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P2137 Throttle/Pedal Position Sensor/Switch B/C Voltage Correlation
The P2137 Throttle/Pedal Position Sensor/Switch B/C Voltage Correlation diagnostic trouble code indicates that the Engine Control Module (ECM/PCM) has detected that the signals from Throttle/Pedal Position Sensor or Switch circuits B and C are not maintaining the expected voltage relationship.
In simple terms, the vehicle's computer compares two electronic throttle or accelerator pedal position signals and determines that Sensor B and Sensor C are not responding in the expected relationship.
Modern vehicles commonly use multiple throttle or accelerator pedal position signals as a safety measure. The ECM continuously compares these signals to make sure the driver's accelerator input can be interpreted correctly. If the relationship between Sensor B and Sensor C falls outside the manufacturer's programmed limits, the ECM can store P2137.
Depending on the vehicle, P2137 may cause the Check Engine Light, reduced engine power, poor throttle response, hesitation, limp mode, poor acceleration, engine surging, rough running, or stalling.
The exact meaning and physical location of Sensors B and C can vary between manufacturers, engines, and model years. The affected circuits may be located in the accelerator pedal assembly, electronic throttle body, or another throttle-position sensing system.
What Does P2137 Mean?
P2137 means that the ECM/PCM has detected a correlation problem between two position-related signals identified as B and C.
The two signals do not necessarily produce the same voltage.
Instead, the ECM expects the signals to maintain a specific relationship as the accelerator pedal or throttle position changes.
For example:
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Both signals may increase as the accelerator pedal is pressed.
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The sensors may operate over different voltage ranges.
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One signal may increase while another decreases.
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The two signals may change at different rates.
The important factor is that their relationship must remain within the expected range.
If Sensor B changes incorrectly relative to Sensor C, the ECM may store P2137.
Why Do Vehicles Use Multiple Throttle and Pedal Sensors?
Modern electronic throttle control systems use redundant position signals for safety.
Unlike older vehicles that used a mechanical throttle cable, many modern vehicles use electronic signals between the accelerator pedal and the engine computer.
A typical system works like this:
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The driver presses the accelerator pedal.
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Accelerator pedal position sensors detect the movement.
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The ECM compares the sensor signals.
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The ECM determines the requested engine torque.
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The ECM commands the electronic throttle actuator.
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Throttle position sensors report actual throttle position.
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The ECM continuously checks the signals for consistency.
If one signal disagrees with the others, the ECM can recognize the problem and activate a protective strategy.
What Does "Voltage Correlation" Mean?
The word correlation is particularly important in P2137.
This code does not simply mean that Sensor B or Sensor C has a high or low voltage.
It means the relationship between the two signals is incorrect.
For example, as the accelerator pedal moves from closed to fully depressed:
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Sensor B should follow its programmed voltage curve.
-
Sensor C should follow its own programmed voltage curve.
The ECM compares both signals.
A correlation fault can occur when:
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Sensor B changes but Sensor C does not.
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Sensor C changes but Sensor B does not.
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One signal suddenly drops.
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One signal suddenly increases.
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One signal becomes intermittent.
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One sensor remains stuck at one value.
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The difference between the two signals becomes excessive.
Where Are Sensors B and C Located?
The location depends on the vehicle.
The affected sensors may be:
Inside the accelerator pedal assembly
Many electronic accelerator pedals contain two or more integrated position sensors.
Inside the electronic throttle body
Electronic throttle bodies may contain multiple throttle position sensors.
Part of another throttle or pedal position system
Some vehicles use different sensor arrangements.
For this reason, the exact meaning of B and C should always be confirmed using vehicle-specific service information.
Symptoms of P2137
Symptoms vary depending on the vehicle and the severity of the sensor disagreement.
Check Engine Light
The Check Engine Light is one of the most common symptoms.
Reduced Engine Power
The ECM may activate a reduced-power strategy.
Poor Throttle Response
The engine may respond slowly or inconsistently to accelerator pedal input.
Poor Acceleration
Engine power may be limited.
Limp Mode
The vehicle may enter a protective operating mode.
Engine Hesitation
The engine may hesitate when the accelerator is pressed.
Inconsistent Acceleration
Throttle response may feel different from normal.
Engine Surging
Some vehicles may experience irregular engine-speed changes.
Rough Idle
An electronic throttle problem may affect idle quality.
Engine Stalling
A severe throttle-control problem can contribute to stalling.
Cruise Control Disabled
Cruise control may be disabled when a throttle or pedal fault is detected.
Warning Messages
Depending on the vehicle, the driver may see messages such as:
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Reduced engine power
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Service throttle system
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Electronic throttle control fault
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Engine fault
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Drive system fault
Common Causes of P2137
Faulty Accelerator Pedal Position Sensor
The accelerator pedal assembly may contain multiple internal sensors.
If Sensor B and Sensor C no longer maintain their expected relationship, P2137 may be triggered.
Possible problems include:
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Internal sensor wear
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Electrical failure
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Signal dropout
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Contamination
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Internal resistance changes
On many vehicles, the sensors are integrated into the pedal assembly, requiring replacement of the complete assembly.
Faulty Electronic Throttle Body
The electronic throttle body may contain:
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Multiple throttle position sensors
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An actuator motor
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Internal electronics
An internal position sensor failure can cause the ECM to detect a B/C correlation problem.
Possible faults include:
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Failed position sensor
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Actuator problem
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Internal electrical failure
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Incorrect throttle-position feedback
Damaged Wiring
A damaged wire can affect one sensor signal while leaving the other signal functional.
Possible causes include:
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Chafing
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Broken wires
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Melted insulation
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Heat damage
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Corrosion
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Engine vibration
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Previous repairs
Corroded Connectors
Corrosion can increase electrical resistance or interrupt a sensor signal.
Inspect connectors for:
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Green corrosion
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White deposits
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Moisture
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Oxidized terminals
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Loose pins
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Damaged connector housings
Loose or Damaged Terminals
A connector can look properly installed while one terminal has poor contact.
Possible problems include:
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Loose terminal tension
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Bent pin
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Backed-out terminal
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Corrosion
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Partially disconnected terminal
This can cause an intermittent P2137.
Short to Ground
A sensor signal wire may contact ground.
This can pull the signal voltage lower than expected and create a disagreement between Sensor B and Sensor C.
Short to Power
A damaged sensor wire may contact:
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Battery voltage
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Ignition power
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Another positive circuit
This can raise the sensor signal above the expected range.
Open Circuit
A broken wire or disconnected connector can interrupt one of the sensor signals.
Possible causes include:
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Broken wiring
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Failed splice
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Damaged connector
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Internal harness damage
Reference-Voltage Problems
Many electronic position sensors use a regulated reference voltage.
A reference-voltage problem can affect one or more sensors simultaneously.
Possible causes include:
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Shorted sensor
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Damaged reference circuit
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Wiring failure
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ECM/PCM circuit problem
Poor Sensor Ground
A poor ground connection can alter the voltage reported by a sensor.
Possible causes include:
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Corroded ground
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Loose terminal
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Damaged sensor ground wire
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ECM/PCM ground problem
Low Battery or Charging-System Voltage
Electronic throttle systems can be sensitive to system voltage.
Possible causes include:
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Weak battery
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Faulty alternator
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Poor battery terminals
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Charging-system wiring problems
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Poor engine grounds
If multiple electrical codes appear at the same time, the vehicle's charging and ground systems should be checked.
Throttle Plate Contamination
Carbon deposits can interfere with throttle plate movement.
Possible symptoms include:
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Sticking throttle plate
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Rough idle
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Poor acceleration
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Reduced throttle response
However, carbon buildup does not automatically mean the throttle position sensors have failed. The throttle body should be tested before replacement.
Mechanical Throttle Binding
A throttle plate that does not move freely may cause abnormal position feedback.
Possible causes include:
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Carbon deposits
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Debris
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Damaged throttle shaft
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Mechanical damage
Incorrect Previous Repairs
Previous repairs can create sensor correlation faults if they result in:
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Incorrect wiring
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Poor splices
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Damaged terminals
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Pinched harnesses
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Incorrect connector installation
Aftermarket Modifications
Possible sources include:
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ECU tuning
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Pedal controllers
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Throttle-response devices
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Modified wiring
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Engine swaps
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Aftermarket engine electronics
Poorly designed modifications can interfere with the expected sensor relationship.
Faulty ECM/PCM
An ECM/PCM fault is possible, but it is generally less common than:
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Sensor failure
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Pedal assembly failure
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Throttle body failure
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Wiring problems
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Connector faults
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Reference-voltage problems
The control module should be considered only after the external circuits have been properly tested.
Vehicles Commonly Affected by P2137
P2137 can occur on many OBD-II vehicles equipped with electronic throttle control systems.
Examples may include:
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Ford F-150
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Ford Explorer
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Ford Mustang
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Ford Focus
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Ford Ranger
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Chevrolet Silverado
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Chevrolet Tahoe
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Chevrolet Malibu
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Chevrolet Camaro
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GMC Sierra
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GMC Yukon
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Cadillac Escalade
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Dodge Charger
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Dodge Challenger
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Ram 1500
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Jeep Grand Cherokee
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Jeep Wrangler
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Chrysler Pacifica
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Toyota Camry
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Toyota Tundra
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Toyota Tacoma
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Honda Accord
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Honda Civic
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Honda CR-V
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Nissan Altima
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Nissan Pathfinder
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Nissan Titan
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BMW 3 Series
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BMW 5 Series
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Mercedes-Benz C-Class
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Mercedes-Benz E-Class
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Volkswagen Golf
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Volkswagen Passat
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Audi A4
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Audi A6
This list is not exhaustive.
P2137 can occur on any compatible vehicle when the ECM detects an abnormal relationship between the relevant B and C throttle/pedal position signals.
Important: Sensor letter assignments are not universal. The exact circuit configuration must be confirmed for the specific vehicle.
How Is P2137 Diagnosed?
Proper diagnosis should identify what Sensors B and C represent on the specific vehicle and determine why their signals no longer correlate.
Check for Additional Trouble Codes
Start with a complete diagnostic scan.
Look for:
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P2137
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Other throttle position codes
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Accelerator pedal position codes
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Throttle actuator codes
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5-volt reference codes
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Sensor circuit codes
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Battery-voltage codes
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Communication codes
Additional codes can significantly narrow down the problem.
Check Freeze-Frame Data
Review the conditions recorded when P2137 was stored.
Important information can include:
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Engine RPM
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Vehicle speed
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Engine load
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Battery voltage
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Accelerator pedal position
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Throttle position
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Coolant temperature
This may reveal whether the problem occurred during acceleration, cruising, idle, or another operating condition.
Identify Sensors B and C
This is one of the most important diagnostic steps.
Use manufacturer service information to identify:
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Sensor B
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Sensor C
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Their physical location
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Their expected voltage ranges
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Their expected relationship
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ECM/PCM terminal locations
Do not assume that Sensor B and Sensor C always refer to the same components on different vehicles.
Monitor Live Data
Use a capable scan tool to monitor:
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Accelerator pedal position
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Throttle position
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Sensor B
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Sensor C
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Commanded throttle position
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Actual throttle position
Slowly operate the accelerator pedal and watch the signals.
A healthy system should show smooth, predictable signal changes.
Look for:
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Dropouts
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Sudden voltage changes
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Frozen readings
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Erratic signals
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One signal changing while the other remains fixed
Check Battery and Charging Voltage
Verify:
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Battery condition
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Battery terminals
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Alternator operation
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Charging voltage
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Engine grounds
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Chassis grounds
Correct system-voltage problems before replacing throttle components.
Inspect the Accelerator Pedal Connector
Check for:
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Corrosion
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Bent pins
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Loose terminals
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Water intrusion
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Damaged locking tabs
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Backed-out terminals
Inspect the Throttle Body Connector
Check for:
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Corrosion
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Heat damage
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Loose terminals
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Broken wiring
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Oil contamination
Inspect Wiring Harnesses
Inspect wiring between the affected sensors and ECM/PCM.
Look for:
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Chafing
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Broken insulation
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Melted wires
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Exposed conductors
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Pinched harnesses
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Poor previous repairs
Pay particular attention to areas where the harness moves or passes near hot engine components.
Check Reference Voltage
Measure the reference voltage according to manufacturer specifications.
Many systems use a regulated 5-volt reference, but the exact specification should be confirmed for the vehicle.
Check:
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Reference voltage
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Sensor ground
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Sensor output
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Wiring continuity
Check for Short Circuits
Test for:
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Short to ground
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Short to power
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Short between sensor circuits
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Internal component shorts
A short can cause one signal to move outside the expected B/C relationship.
Perform Voltage-Drop Testing
Voltage-drop testing can help identify excessive resistance in:
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Power circuits
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Ground circuits
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Connector terminals
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Wiring splices
Test the Accelerator Pedal Assembly
If Sensors B and C are part of the accelerator pedal assembly, test the pedal signals according to manufacturer specifications.
If an internal sensor has failed, replacement of the complete pedal assembly may be required.
Test the Electronic Throttle Body
If the affected sensors are located in the throttle body, test:
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Power supply
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Ground
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Position sensors
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Actuator motor
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Position feedback
Compare the measured values with the manufacturer's specifications.
Inspect the Throttle Plate
If electrical testing is normal, inspect for:
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Carbon buildup
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Mechanical sticking
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Damaged throttle plate
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Restricted movement
Check for Aftermarket Modifications
Inspect:
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Pedal controllers
-
ECU tuning
-
Throttle-response devices
-
Modified wiring
-
Engine swaps
Remove or correct modifications if they are responsible for the correlation fault.
Check ECM/PCM Power and Grounds
Verify:
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Battery power
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Ignition power
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ECM/PCM grounds
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Sensor reference circuits
How to Fix P2137
The correct repair depends on the cause identified during diagnosis.
Replace a Faulty Accelerator Pedal Assembly
If the internal pedal position sensors have failed, replacement of the pedal assembly may be necessary.
Replace a Faulty Electronic Throttle Body
If testing confirms internal throttle position sensor or actuator failure, replace the throttle body or applicable component.
Repair Damaged Wiring
Repair or replace wiring damaged by:
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Heat
-
Chafing
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Corrosion
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Vibration
-
Previous repairs
Repair or Replace Damaged Connectors
Replace damaged connector housings or terminals and ensure proper terminal tension.
Repair Reference-Voltage Problems
Repair damaged:
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Reference-voltage circuits
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Sensor grounds
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Related sensor wiring
Repair Power and Ground Problems
Restore proper:
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Battery connections
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Engine grounds
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Chassis grounds
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ECM/PCM grounds
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Throttle actuator power circuits
Repair Short Circuits
Locate and repair wiring shorted to:
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Ground
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Battery voltage
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Another electrical circuit
Clean the Throttle Body
If carbon buildup is causing mechanical sticking, clean the throttle body according to the manufacturer's procedure.
Avoid damaging the throttle actuator or integrated position sensors.
Correct Previous Repairs
Repair incorrectly connected or poorly repaired wiring.
Correct Aftermarket Modifications
Restore the original throttle-control configuration when modifications are responsible for the fault.
Perform Required Relearn Procedures
Some vehicles may require:
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Throttle body relearn
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Accelerator pedal calibration
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Idle relearn
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Electronic throttle adaptation
Use the correct manufacturer-specific procedure.
Repair or Replace the ECM/PCM
The ECM/PCM should only be considered after all relevant sensors, wiring, connectors, power supplies, grounds, and reference circuits have been tested.
What Happens If P2137 Is Ignored?
Ignoring P2137 can cause continuing throttle-control problems.
Possible consequences include:
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Reduced engine power
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Poor acceleration
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Limp mode
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Engine hesitation
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Rough running
-
Engine stalling
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Poor fuel economy
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Additional throttle-control codes
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Increased emissions
Because redundant throttle and pedal signals are an important safety feature, P2137 should not be ignored.
Can You Drive With P2137?
Driving with P2137 may be possible, but the vehicle should be diagnosed promptly.
A short trip may be possible if:
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The engine runs smoothly.
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Throttle response remains predictable.
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There is no major power loss.
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The vehicle is not stalling.
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The Check Engine Light is not flashing.
Avoid driving if you experience:
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Sudden power loss
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Severe reduction in engine power
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Repeated stalling
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Unpredictable throttle response
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Severe hesitation
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Flashing Check Engine Light
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Multiple warning messages
A serious electronic throttle fault may cause the vehicle to enter reduced-power or limp mode.
Is P2137 a Serious Code?
P2137 is generally considered a moderate to potentially high-severity diagnostic trouble code because it involves electronic throttle or accelerator pedal position signals.
The redundant sensor system is designed to detect incorrect throttle information.
When the ECM detects that the B and C signals no longer correlate correctly, it may limit engine power as a safety precaution.
The fault can affect:
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Throttle response
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Engine power
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Acceleration
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Driveability
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Fuel efficiency
The vehicle should be diagnosed promptly, particularly if reduced-power mode or unpredictable throttle behavior is present.
How to Prevent P2137
Recommended maintenance practices include:
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Keep electrical connectors clean and dry.
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Repair damaged wiring promptly.
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Secure wiring harnesses correctly.
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Maintain battery terminals.
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Maintain engine and chassis grounds.
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Address charging-system problems quickly.
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Keep the throttle body clean when appropriate.
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Avoid poorly designed throttle modifications.
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Avoid low-quality electrical repairs.
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Inspect wiring after major engine repairs.
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Use correct replacement parts.
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Do not ignore Check Engine Light warnings.
P2137 vs. Related Codes
| Code | General Description |
|---|---|
| P2137 | Throttle/Pedal Position Sensor/Switch B/C Voltage Correlation |
| P2138 | Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation |
| P2139 | Throttle/Pedal Position Sensor/Switch D/F Voltage Correlation |
| P2140 | Throttle/Pedal Position Sensor/Switch E/F Voltage Correlation |
| P2136 | Throttle/Pedal Position Sensor/Switch C/D Voltage Correlation |
| P2135 | Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation |
The primary difference is the pair of sensor signals being compared.
P2137 specifically identifies a correlation problem between Sensor B and Sensor C.
Final Thoughts
The P2137 Throttle/Pedal Position Sensor/Switch B/C Voltage Correlation diagnostic trouble code indicates that the ECM/PCM has detected that two position-related signals identified as B and C are no longer maintaining their expected electrical relationship.
Common causes include:
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Faulty accelerator pedal position sensor
-
Faulty electronic throttle body
-
Internal position sensor failure
-
Damaged wiring
-
Corroded connectors
-
Loose terminals
-
Short circuits
-
Open circuits
-
Reference-voltage problems
-
Poor sensor grounds
-
Low system voltage
-
Throttle plate contamination
-
Mechanical throttle binding
-
Incorrect previous repairs
-
Aftermarket modifications
-
ECM/PCM faults
Correct diagnosis begins by identifying exactly what Sensors B and C represent on the specific vehicle.
A capable scan tool should then be used to monitor the sensor signals while the accelerator pedal and throttle position change.
The wiring, connectors, reference voltage, grounds, and power supply should be tested before replacing components.
P2137 does not automatically mean that the accelerator pedal assembly or throttle body needs to be replaced. A damaged wire, poor connector, bad ground, reference-voltage problem, or another electrical fault can produce the same correlation code.
Finding the actual reason why the B and C signals no longer agree is essential for restoring reliable throttle operation, proper engine performance, and safe vehicle driveability.
