P2108 Throttle Actuator Control Module Performance

The P2108 Throttle Actuator Control Module Performance diagnostic trouble code indicates that the Engine Control Module (ECM/PCM) has detected a performance problem with the Throttle Actuator Control (TAC) system or its control module.

In simple terms, the vehicle's computer has determined that the electronic throttle-control system is not operating as expected.

Modern vehicles use an Electronic Throttle Control (ETC) system instead of a traditional mechanical accelerator cable. The system electronically controls the throttle opening based on accelerator-pedal input, engine operating conditions, traction requirements, emissions demands, and other parameters.

When the ECM/PCM detects that the throttle actuator control system or its control module is not performing within the expected parameters, it can store P2108.

Depending on the vehicle, the fault may cause:

• Check Engine Light

• Reduced engine power

• Limp mode

• Limited engine RPM

• Poor accelerator response

• Throttle hesitation

• Unstable idle

• Cruise-control deactivation

• Electronic throttle warning

• Reduced Power warning

P2108 is a system-performance code, so it does not automatically mean that the throttle-control module itself has failed. The underlying problem may be the throttle body, actuator motor, position sensors, wiring, power supply, grounds, communication circuit, accelerator pedal, or software/calibration.

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What Does P2108 Mean?

P2108 means that the ECM/PCM has detected that the Throttle Actuator Control system is not performing correctly.

The code description contains several important terms:

Throttle Actuator Control

The TAC system controls the electronic throttle plate.

It generally includes:

• Accelerator-pedal position sensors

• Throttle actuator motor

• Throttle-position sensors

• Electronic throttle body

• Wiring and connectors

• ECM/PCM or a dedicated throttle-control module

• Related software and calibration

Module

Depending on the vehicle, throttle control may be handled directly by the ECM/PCM or through a separate control module.

The exact architecture varies considerably between manufacturers.

Performance

"Performance" means the control system has detected that its operation does not match the expected behavior.

This can involve:

• Throttle position

• Throttle movement

• Motor operation

• Sensor feedback

• Module communication

• Electrical supply

• Internal control logic

• Learned/adapted throttle values

Therefore, P2108 should be treated as a system-level fault rather than proof that one particular component is defective.

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How Does the Throttle Actuator Control System Work?

A typical electronic throttle-control system operates through several coordinated components.

1. The driver presses the accelerator pedal.

2. Accelerator-pedal position sensors detect pedal movement.

3. Redundant pedal signals are transmitted to the ECM/PCM.

4. The ECM calculates the driver's requested torque.

5. The ECM determines the appropriate throttle opening.

6. The throttle actuator motor moves the throttle plate.

7. Throttle-position sensors report the actual throttle position.

8. The ECM compares commanded and actual throttle positions.

9. The ECM continuously checks sensor correlation and actuator performance.

10. If the throttle system does not respond as expected, a fault can be stored.

The system is designed with redundancy because electronic throttle control directly affects engine torque.

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Why Does the Vehicle Need Electronic Throttle Control?

Electronic throttle control provides the ECM with precise control over engine airflow.

It allows the vehicle to manage:

• Engine idle speed

• Acceleration

• Fuel economy

• Emissions

• Cruise control

• Traction control

• Stability-control interventions

• Engine torque management

• Automatic-transmission torque reduction

Because the throttle system is integrated with many vehicle functions, a TAC fault can produce symptoms beyond simple engine hesitation.

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Symptoms of P2108

Symptoms vary by vehicle and by the underlying cause.

Check Engine Light

The Check Engine Light is one of the most common symptoms.

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Reduced Engine Power

The ECM may limit engine torque when it cannot reliably control the throttle.

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Limp Mode

The vehicle may enter a fail-safe operating mode.

Possible limitations include:

• Maximum engine RPM

• Throttle opening

• Engine torque

• Accelerator response

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Poor Accelerator Response

The accelerator pedal may feel delayed or less responsive.

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Limited Acceleration

The vehicle may struggle to accelerate normally.

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Throttle Hesitation

There may be a delay between pressing the accelerator and the engine responding.

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Rough or Unstable Idle

A throttle-control problem can interfere with precise idle-air management.

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High Idle

If the throttle plate does not return correctly, engine airflow may remain higher than commanded.

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Engine Stalling

A severe throttle-control fault can contribute to stalling, especially when the throttle closes toward idle.

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Engine Surging

Incorrect throttle control can sometimes cause unwanted changes in engine speed.

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Cruise Control Not Working

Cruise control may be disabled when a TAC fault is present.

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Electronic Throttle Warning

Some vehicles may illuminate a dedicated electronic throttle-control warning.

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Reduced Power Message

Certain vehicles may display a Reduced Engine Power or similar warning when the ECM enters fail-safe operation.

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Common Causes of P2108

Faulty Throttle Body

A defective electronic throttle body is one possible cause.

The throttle body may contain:

• Actuator motor

• Throttle-position sensors

• Internal gears

• Throttle plate

• Position-sensor electronics

An internal failure can prevent the throttle from responding correctly.

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Throttle Actuator Motor Problem

The electric motor may have:

• Excessive current draw

• Open circuit

• Short circuit

• Internal wear

• Mechanical binding

• Intermittent operation

A motor problem can prevent the throttle plate from reaching the commanded position.

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Dirty Throttle Body

Carbon and deposits can interfere with throttle-plate movement.

Deposits may form around:

• Throttle plate edges

• Throttle bore

• Throttle shaft

A dirty throttle body may cause the motor to work harder or prevent consistent movement.

However, P2108 should not automatically be diagnosed as a dirty throttle body.

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Throttle Plate Binding

The throttle plate may stick or move inconsistently.

Possible causes include:

• Carbon deposits

• Dirt

• Foreign material

• Damaged throttle plate

• Bent shaft

• Internal mechanical wear

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Faulty Throttle Position Sensor

Electronic throttle bodies normally use one or more position sensors.

A faulty sensor can cause the ECM to see:

• Incorrect throttle position

• Signal dropout

• Erratic readings

• Incorrect minimum position

• Incorrect maximum position

• Sensor correlation problems

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Accelerator Pedal Position Sensor Problem

The accelerator pedal typically contains redundant position sensors.

A problem with the pedal signal can prevent the ECM from correctly determining the driver's requested throttle position.

Possible problems include:

• Internal sensor wear

• Signal dropout

• Incorrect voltage

• Wiring damage

• Connector problems

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Damaged Wiring

The TAC system depends on multiple electrical circuits.

Possible wiring problems include:

• Broken wires

• Chafing

• Heat damage

• Melted insulation

• Pinched wires

• Short circuits

• Open circuits

• Poor previous repairs

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Corroded Connectors

Water intrusion or corrosion can increase resistance or interrupt electrical signals.

Inspect for:

• Corroded terminals

• Loose pins

• Bent pins

• Water intrusion

• Poor terminal tension

• Damaged connector housings

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Power Supply Problem

The throttle-control system requires stable electrical power.

Problems can result from:

• Weak battery

• Poor battery connections

• Blown fuse

• Voltage drop

• Damaged power wire

• Poor ground

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Poor Ground Connection

A bad ground can cause abnormal module or sensor operation.

Possible causes include:

• Corrosion

• Loose ground connection

• Damaged ground cable

• High resistance

• Poor engine-to-chassis ground

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Low Battery Voltage

Low system voltage can interfere with electronic throttle operation.

A weak battery may be particularly relevant if the code appears:

• During starting

• After the vehicle has been parked

• During cold weather

• Alongside other low-voltage codes

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Charging-System Problems

A failing alternator or voltage regulator can produce unstable electrical voltage.

This can affect electronic throttle control.

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Throttle Adaptation Problem

Many vehicles require the ECM to learn throttle-body positions.

An adaptation problem may occur after:

• Throttle-body cleaning

• Throttle-body replacement

• Battery disconnection

• ECM replacement

• Software updates

If the required adaptation is not completed, the ECM may detect abnormal throttle performance.

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Software or Calibration Problem

A software issue can sometimes cause incorrect TAC monitoring.

Possible solutions may include:

• ECM software update

• Module programming

• Calibration update

• Throttle relearn

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Communication Problem

On vehicles with a separate throttle-control module, communication between modules may be relevant.

Possible causes include:

• CAN-bus wiring problems

• Communication interruption

• Module power-supply problems

• Ground problems

• Connector damage

• Module software problems

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Faulty Throttle Actuator Control Module

Some vehicles use a dedicated TAC module.

If the module itself has an internal fault, P2108 may be stored.

However, the module should not be replaced simply because P2108 is present.

Power, ground, communication, input signals, output signals, and related components should be tested first.

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Faulty ECM/PCM

In some vehicles, the ECM/PCM directly controls the throttle actuator.

An internal ECM/PCM problem is possible but is generally less common than problems involving:

• Throttle body

• Position sensors

• Wiring

• Connectors

• Battery voltage

• Grounds

• Adaptation

• Software

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Vehicles Commonly Affected by P2108

P2108 can occur on many OBD-II vehicles equipped with electronic throttle-control systems.

Examples may include:

• Ford F-150

• Ford Mustang

• Ford Explorer

• Ford Focus

• Ford Escape

• Ford Fusion

• Ford Ranger

• Chevrolet Silverado

• Chevrolet Tahoe

• Chevrolet Suburban

• Chevrolet Camaro

• Chevrolet Malibu

• GMC Sierra

• GMC Yukon

• Cadillac Escalade

• Dodge Charger

• Dodge Challenger

• Ram 1500

• Jeep Grand Cherokee

• Jeep Wrangler

• Chrysler Pacifica

• Toyota Camry

• Toyota Corolla

• Toyota Tundra

• Toyota Tacoma

• Honda Accord

• Honda Civic

• Honda CR-V

• Nissan Altima

• Nissan Pathfinder

• Nissan Titan

• BMW 3 Series

• BMW 5 Series

• Mercedes-Benz C-Class

• Mercedes-Benz E-Class

• Volkswagen Golf

• Volkswagen Passat

• Audi A4

• Audi A6

This list is not exhaustive.

P2108 is a generic OBD-II code, but the exact throttle-control architecture and diagnostic procedure can differ significantly between manufacturers.

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How Is P2108 Diagnosed?

P2108 should be diagnosed as a system-performance problem rather than simply replacing the throttle body or control module.

A systematic diagnostic process is important.

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Check for Additional Trouble Codes

Perform a complete scan of the vehicle.

Pay particular attention to codes involving:

• Throttle position

• Accelerator pedal position

• Throttle actuator motor

• Minimum-stop performance

• Maximum-stop performance

• Sensor correlation

• 5-volt reference

• Battery voltage

• CAN communication

Related codes may include:

• P2100

• P2101

• P2102

• P2103

• P2104

• P2105

• P2106

• P2107

• P2109

• P2110

• P2111

• P2112

• P2113

• P2114

• P2115

• P2116

• P2117

• P2118

• P2119

• P2120

• P2121

• P2122

• P2123

• P2124

• P2125

• P2126

• P2127

• P2128

• P2129

• P2130

• P2131

• P2132

• P2133

• P2134

• P2135

• P2136

• P2137

• P2138

• P2139

• P2140

The presence of additional codes can significantly narrow the diagnostic path.

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Check Freeze-Frame Data

Review the operating conditions when P2108 was stored.

Important information includes:

• Engine RPM

• Vehicle speed

• Accelerator-pedal position

• Commanded throttle position

• Actual throttle position

• Throttle sensor values

• Battery voltage

• Engine coolant temperature

• Engine load

Determine whether the fault occurred:

• During startup

• At idle

• During acceleration

• During deceleration

• During rapid throttle movement

• At a specific temperature

• Under high electrical load

This can be particularly useful for intermittent faults.

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Monitor Throttle Position Data

Use a capable scan tool to compare:

• Commanded throttle position

• Actual throttle position

• Accelerator-pedal position

• Redundant sensor signals

The throttle position should follow the commanded value smoothly.

Look for:

• Delayed movement

• Signal dropouts

• Sudden jumps

• Incorrect closed-throttle value

• Incorrect maximum value

• Inconsistent sensor correlation

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Command the Throttle Actuator

Where supported by the diagnostic equipment and manufacturer procedure, command the throttle actuator through different positions.

Observe whether:

• The throttle moves smoothly.

• The motor responds consistently.

• The actual position follows the commanded position.

• The throttle returns correctly.

• The position sensors remain stable.

A failure to respond to a commanded position can help distinguish an actuator/mechanical problem from a sensor problem.

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Inspect the Throttle Body

Inspect the throttle body for:

• Carbon deposits

• Dirt

• Foreign objects

• Damaged throttle plate

• Binding

• Internal gear damage

• Signs of overheating

If cleaning is appropriate, follow the manufacturer's procedure.

Do not force an electronic throttle plate manually if the manufacturer prohibits doing so.

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Check Throttle Actuator Motor Current

If specifications are available, check actuator motor current.

Abnormal current can indicate:

• Mechanical binding

• Motor wear

• Internal damage

• Electrical resistance

• Short circuit

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Check Accelerator Pedal Signals

Monitor the accelerator-pedal position sensors.

The signals should change smoothly as the pedal is pressed and released.

Look for:

• Dead spots

• Signal dropout

• Sudden jumps

• Incorrect minimum values

• Incorrect maximum values

• Correlation errors

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Check the 5-Volt Reference

Measure the relevant reference voltage according to the manufacturer's procedure.

If several sensors share the same reference circuit, determine whether another component is affecting the reference voltage.

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Check Sensor Grounds

Check the sensor and module grounds for:

• High resistance

• Voltage drop

• Corrosion

• Loose connections

• Damaged wiring

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Inspect Wiring and Connectors

Inspect the complete TAC circuit.

Pay particular attention to areas near:

• Throttle body

• Accelerator pedal

• Engine harness

• Exhaust components

• Battery

• Ground points

Look for:

• Broken wires

• Chafing

• Melted insulation

• Corrosion

• Water intrusion

• Loose pins

• Backed-out terminals

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Perform a Wiggle Test

While monitoring throttle and pedal sensor data, carefully move the relevant harnesses and connectors.

If the signal changes unexpectedly, investigate the wiring or connector.

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Check Battery and Charging Voltage

Verify:

• Battery condition

• Battery terminals

• Charging voltage

• Alternator operation

• Engine grounds

• Chassis grounds

A throttle-control fault accompanied by low system voltage should be investigated for a power-supply problem before replacing expensive components.

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Check Module Communication

If the vehicle uses a separate throttle actuator control module, verify communication between the module and ECM/PCM.

Inspect:

• CAN wiring

• Module power

• Module grounds

• Communication connectors

• Related communication codes

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Perform Throttle Relearn or Adaptation

If required by the manufacturer, perform the appropriate throttle adaptation procedure.

This may be necessary after:

• Throttle-body cleaning

• Throttle-body replacement

• Accelerator-pedal replacement

• Battery disconnection

• ECM replacement

• Module replacement

A generic internet throttle-relearn procedure should not automatically be used on every vehicle.

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Check Technical Service Bulletins

Manufacturer service information may identify known issues involving:

• TAC module failures

• Throttle-body failures

• Sensor calibration

• Wiring defects

• Software problems

• Connector issues

• Required adaptations

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How to Fix P2108

The correct repair depends on the confirmed cause.

Clean the Throttle Body

If deposits are preventing proper throttle movement, clean the throttle body according to the manufacturer's procedure.

Perform the required adaptation afterward.

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Repair Mechanical Throttle Binding

If the throttle plate or internal mechanism is binding, repair or replace the affected throttle-body assembly.

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Replace the Throttle Body

If testing confirms an internal failure involving the actuator motor, position sensors, gears, or electronics, replace the throttle body.

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Replace a Faulty Accelerator Pedal

If testing confirms an internal accelerator-pedal position sensor fault, replace the pedal assembly where required.

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Repair Wiring

Repair damaged wiring caused by:

• Chafing

• Heat

• Vibration

• Corrosion

• Pinching

• Previous repairs

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Repair Connectors

Replace damaged terminals or connector housings and restore proper terminal tension.

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Repair Power or Ground Problems

Correct:

• Low battery voltage

• Poor grounds

• Voltage drops

• Blown fuses

• Damaged power circuits

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Repair Communication Problems

If a separate TAC module is used, repair CAN-bus or other communication faults.

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Replace the TAC Module

If the vehicle has a dedicated throttle actuator control module and testing confirms an internal module failure, replace and program the module according to manufacturer procedures.

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Update or Reprogram the ECM/PCM

If manufacturer information identifies a software or calibration problem, update or reprogram the relevant module.

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Replace the ECM/PCM

ECM/PCM replacement should only be considered after all related sensors, actuators, wiring, power supplies, grounds, communication circuits, and software have been properly tested.

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What Happens If P2108 Is Ignored?

P2108 should not be ignored because the throttle actuator control system directly affects engine torque.

Possible consequences include:

• Reduced engine power

• Limp mode

• Limited acceleration

• Poor throttle response

• Unstable idle

• Engine stalling

• Cruise-control deactivation

• Additional throttle-control codes

• Increased emissions

In severe cases, the vehicle may enter a fail-safe mode with very limited throttle operation.

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Can You Drive With P2108?

Driving with P2108 depends heavily on the symptoms.

A vehicle that still has normal and predictable accelerator response may be temporarily driveable, but the fault should be diagnosed promptly.

A short trip may be possible if:

• The engine runs normally.

• Accelerator response is predictable.

• There is no significant loss of power.

• The engine does not stall.

• No severe warning messages are displayed.

Avoid continued driving if there is:

• Sudden loss of acceleration

• Unpredictable throttle response

• Severe hesitation

• Repeated stalling

• Reduced-power mode

• Very limited RPM

• Electronic throttle warnings

If throttle response becomes unpredictable, the vehicle should be inspected as soon as possible.

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Is P2108 a Serious Code?

P2108 is generally considered a moderate to high-severity diagnostic trouble code.

The throttle actuator control system is directly responsible for controlling engine airflow and therefore engine torque.

The severity becomes higher when the vehicle experiences:

• Reduced engine power

• Limp mode

• Stalling

• Unpredictable acceleration

• Severe throttle hesitation

• Inability to maintain normal speed

If the vehicle suddenly loses throttle response or enters reduced-power mode, the problem should be treated as a high-priority repair.

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P2108 vs. Related Throttle Actuator Codes

Code	General Description
P2108	Throttle Actuator Control Module Performance
P2109	Throttle/Pedal Position Sensor "A" Minimum Stop Performance
P2110	Throttle Actuator Control System Forced Limited RPM
P2111	Throttle Actuator Control System Stuck Open
P2112	Throttle Actuator Control System Stuck Closed
P2113	Throttle/Pedal Position Sensor "B" Minimum Stop Performance
P2114	Throttle/Pedal Position Sensor "C" Minimum Stop Performance
P2115	Throttle/Pedal Position Sensor "D" Minimum Stop Performance
P2116	Throttle/Pedal Position Sensor "E" Minimum Stop Performance
P2117	Throttle/Pedal Position Sensor "F" Minimum Stop Performance
P2118	Throttle Actuator Control Motor Current Range/Performance
P2119	Throttle Actuator Control Throttle Body Range/Performance
P2120	Throttle/Pedal Position Sensor/Switch "D" Circuit Malfunction
P2121	Throttle/Pedal Position Sensor/Switch "D" Circuit Range/Performance
P2122	Throttle/Pedal Position Sensor/Switch "D" Circuit Low Input
P2123	Throttle/Pedal Position Sensor/Switch "D" Circuit High Input
P2124	Throttle/Pedal Position Sensor/Switch "D" Circuit Intermittent
P2125	Throttle/Pedal Position Sensor/Switch "E" Circuit Malfunction
P2126	Throttle/Pedal Position Sensor/Switch "E" Circuit Range/Performance
P2127	Throttle/Pedal Position Sensor/Switch "E" Circuit Low Input
P2128	Throttle/Pedal Position Sensor/Switch "E" Circuit High Input
P2129	Throttle/Pedal Position Sensor/Switch "E" Circuit Intermittent
P2130	Throttle/Pedal Position Sensor/Switch "F" Circuit Malfunction
P2131	Throttle/Pedal Position Sensor/Switch "F" Circuit Range/Performance
P2132	Throttle/Pedal Position Sensor/Switch "F" Circuit Low Input
P2133	Throttle/Pedal Position Sensor/Switch "F" Circuit High Input
P2134	Throttle/Pedal Position Sensor/Switch "F" Circuit Intermittent
P2135	Throttle Position Sensor A/B Voltage Correlation

The distinction is important:

• P2108 focuses on Throttle Actuator Control Module/system performance.

• P2109 focuses on minimum-stop performance of throttle/pedal sensor "A".

• P2110 indicates that the TAC system has forced the engine to limited RPM.

• P2111 indicates that the throttle-control system is stuck open.

• P2112 indicates that the throttle-control system is stuck closed.

• P2113–P2117 concern minimum-stop performance of specific throttle/pedal sensor channels.

• P2118 concerns throttle actuator motor current range/performance.

• P2119 concerns throttle-body range/performance.

• P2120–P2124 concern the "D" throttle/pedal sensor circuit.

• P2125–P2129 concern the "E" throttle/pedal sensor circuit.

• P2130–P2134 concern the "F" throttle/pedal sensor circuit.

• P2135 concerns throttle-position sensor A/B voltage correlation.

If P2108 appears together with another throttle or pedal-position code, the combination can be much more useful diagnostically than P2108 by itself.

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How to Prevent P2108

Recommended practices include:

• Keep the throttle body clean according to manufacturer recommendations.

• Follow the correct procedure when cleaning an electronic throttle body.

• Perform required throttle adaptation after applicable repairs.

• Protect throttle and accelerator-pedal wiring from heat.

• Prevent wiring from rubbing against metal.

• Keep electrical connectors clean and dry.

• Maintain battery terminals.

• Maintain engine and chassis grounds.

• Maintain the charging system.

• Address low-voltage problems promptly.

• Use correct throttle-body and accelerator-pedal components.

• Avoid poorly installed throttle-control modifications.

• Address Check Engine Light warnings promptly.

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Final Thoughts

The P2108 Throttle Actuator Control Module Performance diagnostic trouble code indicates that the ECM/PCM has detected abnormal performance from the electronic throttle actuator-control system.

Possible causes include:

• Faulty throttle body

• Throttle actuator motor problems

• Dirty or binding throttle plate

• Faulty throttle-position sensors

• Accelerator-pedal position sensor problems

• Damaged wiring

• Corroded connectors

• Poor power supply

• Poor grounds

• Low battery voltage

• Charging-system problems

• Throttle adaptation problems

• CAN-bus or module communication faults

• Software/calibration problems

• Faulty TAC module

• ECM/PCM problems

The most important point is that P2108 does not automatically mean the throttle-control module or throttle body needs to be replaced.

A proper diagnosis should begin with a complete scan for related codes and freeze-frame data. The technician should then compare commanded and actual throttle position, monitor accelerator-pedal and throttle-position sensor signals, inspect the throttle body and actuator, check motor operation and current where applicable, verify the 5-volt reference and sensor grounds, inspect wiring and connectors, test battery and charging voltage, verify module communication where applicable, and perform the required throttle adaptation or relearn procedure.

If the vehicle has severe power loss, unpredictable accelerator response, repeated stalling, or reduced-power mode, the fault should be diagnosed promptly because the electronic throttle system is directly responsible for controlling engine airflow and engine torque.