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P2136 Throttle/Pedal Position Sensor/Switch A/C Voltage Correlation
The P2136 Throttle/Pedal Position Sensor/Switch A/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 A and C are not maintaining the expected voltage relationship.
In simple terms, the vehicle's computer is comparing two throttle or accelerator pedal position signals and has determined that Sensor A and Sensor C do not agree with each other as expected.
Modern vehicles use multiple position sensors as part of the electronic throttle control system. These redundant signals allow the ECM to verify accelerator pedal and throttle position and detect faults before they cause unsafe throttle operation.
If the relationship between Sensor A and Sensor C falls outside the manufacturer's programmed limits, the ECM may store P2136 and activate a protective strategy.
Depending on the vehicle, symptoms may include 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 A and C vary between manufacturers. The affected circuits may be located in the accelerator pedal assembly, electronic throttle body, or another throttle/pedal position sensing system.
What Does P2136 Mean?
P2136 means that the ECM/PCM has detected a correlation problem between two position-related signals identified as A and C.
The two sensors do not necessarily produce identical voltage readings.
Instead, the ECM expects them 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 two sensors may operate across different voltage ranges.
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One signal may increase while another decreases.
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The signals may change at different rates.
The important factor is that the relationship between the signals must remain within a predefined range.
If Sensor A changes incorrectly relative to Sensor C, P2136 may be stored.
Why Do Vehicles Use Multiple Throttle and Pedal Position Sensors?
Modern electronic throttle control systems use redundant position signals for safety and reliability.
Unlike older vehicles that used a mechanical throttle cable, many modern vehicles electronically transmit the driver's accelerator input to the ECM.
A typical system works as follows:
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The driver presses the accelerator pedal.
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Position sensors detect pedal movement.
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The ECM monitors the sensor signals.
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The ECM compares the signals with each other.
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The ECM calculates the driver's requested engine torque.
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The ECM commands the electronic throttle actuator.
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Throttle position sensors report actual throttle movement.
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The ECM continuously checks the signals for consistency.
If the signals do not correlate correctly, the ECM can reduce engine power or enter a fail-safe mode.
What Does "Voltage Correlation" Mean?
The word correlation is important in P2136.
This code does not necessarily mean that Sensor A or Sensor C simply has a high or low voltage.
Instead, it means that the relationship between the two signals is outside the expected range.
For example, when the accelerator pedal moves:
-
Sensor A should follow its programmed signal pattern.
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Sensor C should follow its own programmed signal pattern.
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The relationship between both signals should remain predictable.
A correlation fault may occur when:
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Sensor A changes but Sensor C does not.
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Sensor C changes but Sensor A 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 becomes stuck at one value.
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The difference between the two signals becomes excessive.
Where Are Sensors A and C Located?
The exact location depends on the vehicle.
The affected sensors may be:
Inside the accelerator pedal assembly
Many accelerator pedal assemblies contain multiple integrated position sensors.
Inside the electronic throttle body
Some throttle bodies contain multiple throttle position sensors.
Part of another throttle or pedal position system
Some manufacturers use different sensor configurations.
For this reason, the exact meaning of Sensor A and Sensor C should be confirmed using vehicle-specific service information.
Symptoms of P2136
The symptoms depend on the vehicle and how far the sensor signals have deviated from the expected relationship.
Check Engine Light
The Check Engine Light is one of the most common symptoms.
Reduced Engine Power
The ECM may limit engine output to protect the vehicle.
Poor Throttle Response
The engine may respond slowly or inconsistently to accelerator input.
Poor Acceleration
The vehicle may have noticeably reduced acceleration.
Limp Mode
The vehicle may enter a protective operating mode.
Engine Hesitation
Hesitation may occur when pressing the accelerator.
Inconsistent Acceleration
Engine response may not match pedal movement normally.
Engine Surging
Some vehicles may experience irregular changes in engine speed.
Rough Idle
Electronic throttle problems can affect idle quality.
Engine Stalling
A severe position-sensor fault can contribute to stalling.
Cruise Control Problems
Cruise control may be disabled.
Warning Messages
Depending on the vehicle, the dashboard may display 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 P2136
Faulty Accelerator Pedal Position Sensor
The accelerator pedal may contain multiple internal sensors.
If Sensor A and Sensor C no longer maintain their expected relationship, P2136 can be triggered.
Possible failures 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 position sensors are integrated into the accelerator pedal and the complete pedal assembly may need to be replaced.
Faulty Electronic Throttle Body
An electronic throttle body may contain:
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Multiple throttle position sensors
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An electric actuator motor
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Internal electronic circuits
An internal sensor failure can cause an A/C correlation fault.
Possible problems include:
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Failed position sensor
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Internal electrical failure
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Actuator problems
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Incorrect position feedback
Damaged Wiring
A damaged wire can affect one sensor signal while the other continues working.
Possible causes include:
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Chafing
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Broken wires
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Melted insulation
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Exhaust heat
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Engine vibration
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Corrosion
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Previous repair damage
Corroded Electrical Connectors
Corrosion can create electrical resistance or interrupt a sensor signal.
Inspect 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 may appear properly connected while one terminal has poor contact.
Possible problems include:
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Loose terminal tension
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Bent terminal
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Backed-out terminal
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Corrosion
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Partially disconnected terminal
This can cause an intermittent P2136.
Short to Ground
A sensor signal wire may contact ground.
This can pull one signal lower than expected and cause a mismatch between Sensor A and Sensor C.
Short to Power
A sensor signal wire may contact:
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Battery voltage
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Ignition power
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Another positive electrical circuit
This can force the signal higher than expected.
Open Circuit
A broken wire or disconnected connector can interrupt one of the position sensor signals.
Possible causes include:
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Broken wiring
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Damaged connector
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Failed splice
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Internal harness damage
Reference-Voltage Problems
Many electronic position sensors use a regulated reference voltage.
A problem with the reference circuit can affect one or more sensors.
Possible causes include:
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Shorted sensor
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Damaged reference-voltage wire
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Wiring failure
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ECM/PCM circuit problem
Poor Sensor Ground
A poor ground can change the voltage reported by a position sensor.
Possible causes include:
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Corroded ground connection
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Loose terminal
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Damaged sensor ground
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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 several unrelated electrical codes appear together, battery and charging-system testing should be performed.
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
Carbon buildup does not automatically mean that the position sensors have failed. The throttle body should be tested before replacement.
Mechanical Throttle Binding
A throttle plate that does not move freely can cause abnormal position feedback.
Possible causes include:
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Carbon buildup
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Debris
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Damaged throttle shaft
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Mechanical damage
Incorrect Previous Repairs
Previous repairs can cause sensor correlation problems if they result in:
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Incorrect wiring
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Poor splices
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Pinched wiring
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Damaged terminals
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Incorrect connector installation
Aftermarket Modifications
Potential 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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Accelerator pedal 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 ECM/PCM should only be considered after the relevant external circuits have been properly tested.
Vehicles Commonly Affected by P2136
P2136 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.
P2136 can occur on any compatible vehicle when the ECM detects an abnormal relationship between the relevant A and C position sensor signals.
Important: Sensor letter assignments are not universal. Always verify the exact circuit identification for the vehicle being diagnosed.
How Is P2136 Diagnosed?
Proper diagnosis should identify what Sensors A and C represent on the specific vehicle and determine why their signals no longer correlate correctly.
Check for Additional Trouble Codes
Start with a complete diagnostic scan.
Look for:
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P2136
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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 help identify whether the problem is related to the pedal, throttle body, wiring, or power supply.
Check Freeze-Frame Data
Review the freeze-frame information captured when P2136 was stored.
Important parameters may 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 can help determine the conditions under which the sensor correlation failed.
Identify Sensors A and C
This is one of the most important diagnostic steps.
Use manufacturer service information to identify:
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Sensor A
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Sensor C
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Their physical location
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Expected voltage ranges
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Expected signal relationship
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ECM/PCM terminal locations
Do not assume that Sensor A and Sensor C have the same meaning on another vehicle.
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 A
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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 observe the signals.
A healthy system should show smooth and predictable changes.
Look for:
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Signal dropouts
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Sudden jumps
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Frozen values
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Erratic changes
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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 terminal connections
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Alternator output
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Charging voltage
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Engine grounds
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Chassis grounds
Repair system-voltage problems before replacing throttle-control 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 the 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 close to hot engine components.
Check Reference Voltage
Measure the relevant reference voltage according to manufacturer specifications.
Many systems use a 5-volt reference, but the exact specification must 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 circuit can cause one signal to move outside the expected A/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 A and C are part of the accelerator pedal assembly, test the individual signals according to manufacturer specifications.
If an internal sensor has failed, the complete accelerator pedal assembly may require replacement.
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 results with manufacturer specifications.
Inspect the Throttle Plate
If electrical testing is normal, inspect the throttle body for:
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Carbon buildup
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Mechanical sticking
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Damaged throttle plate
-
Restricted movement
Check for Aftermarket Modifications
Inspect:
-
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 P2136
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
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Chafing
-
Corrosion
-
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
-
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
-
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 P2136 Is Ignored?
Ignoring P2136 can cause continuing throttle-control problems.
Possible consequences include:
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Reduced engine power
-
Poor acceleration
-
Limp mode
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Engine hesitation
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Rough running
-
Engine stalling
-
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, P2136 should not be ignored.
Can You Drive With P2136?
Driving with P2136 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
If the vehicle enters reduced-power mode or throttle response becomes unpredictable, it should be inspected before continued driving.
Is P2136 a Serious Code?
P2136 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 identify incorrect throttle information.
When the ECM detects that the A 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
-
Acceleration
-
Driveability
-
Fuel efficiency
The vehicle should be diagnosed promptly, especially if reduced-power mode or unpredictable throttle behavior is present.
How to Prevent P2136
Recommended 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.
-
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.
P2136 vs. Related Codes
| Code | General Description |
|---|---|
| P2136 | Throttle/Pedal Position Sensor/Switch A/C Voltage Correlation |
| 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 |
| P2135 | Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation |
The primary difference is the pair of sensor signals being compared.
P2136 specifically identifies a correlation problem between Sensor A and Sensor C.
Final Thoughts
The P2136 Throttle/Pedal Position Sensor/Switch A/C Voltage Correlation diagnostic trouble code indicates that the ECM/PCM has detected that two position-related signals identified as A and C are no longer maintaining their expected electrical relationship.
Common causes include:
-
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 A 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.
P2136 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 failure.
Finding the actual reason why the A and C signals no longer agree is essential for restoring reliable throttle operation, proper engine performance, and safe vehicle driveability.
