31-01-2025
12 min.
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P2142 Exhaust Gas Recirculation (EGR) Throttle Control Circuit "A" High

The P2142 Exhaust Gas Recirculation (EGR) Throttle Control Circuit "A" High diagnostic trouble code indicates that the Engine Control Module (ECM/PCM) has detected an electrical voltage or signal that is higher than expected in the EGR throttle control circuit identified as "A."

In simple terms, the vehicle's computer is seeing too much voltage in part of the electrical system used to control the EGR throttle.

The EGR throttle is often used to help regulate airflow and create the conditions required for proper exhaust gas recirculation. This component is especially common on many modern diesel engines, although similar systems may also be found on certain gasoline engines.

When the EGR throttle control circuit signal becomes too high, the ECM may no longer be able to accurately control the component. This can cause problems with EGR operation, engine airflow, emissions, performance, and fuel efficiency.

Depending on the vehicle, P2142 may cause the Check Engine Light, reduced engine power, hesitation, poor acceleration, rough running, increased emissions, poor fuel economy, or limp mode.

The exact meaning of Circuit "A" and the EGR throttle configuration can vary by manufacturer, engine, and model year. Therefore, diagnosis should always use vehicle-specific service information.

What Does P2142 Mean?

P2142 means that the ECM/PCM has detected a higher-than-expected electrical condition in the EGR throttle control circuit "A."

The word "High" normally refers to an electrical voltage or control signal, not necessarily excessive airflow or excessive exhaust gas flow.

Possible causes include:

Short to battery voltage
Shorted control wiring
Damaged wiring harness
Faulty EGR throttle actuator
Internal actuator electrical fault
Corroded or damaged connector
Incorrect voltage supply
Faulty power-distribution circuit
Incorrect previous wiring repair
Aftermarket electrical modifications
Faulty ECM/PCM

A P2142 code does not automatically mean that the throttle plate is physically stuck open.

The fault may be entirely electrical.

What Is the EGR Throttle?

The term EGR throttle can describe an electronically controlled air-management component that works with the EGR system.

Depending on the engine design, the throttle may:

Restrict intake airflow when required
Help create a pressure difference for EGR flow
Support exhaust gas recirculation
Assist emissions control
Help manage engine shutdown on some diesel engines
Control airflow during certain operating conditions

On diesel engines, the EGR throttle can sometimes be called:

Intake throttle valve
Air shutoff valve
Anti-shudder valve
Intake air control valve
Throttle valve actuator

The exact terminology varies by manufacturer.

How Does the EGR Throttle System Work?

The ECM/PCM constantly monitors engine operating conditions and controls airflow as necessary.

Information can come from sensors such as:

Mass airflow sensor
Manifold absolute pressure sensor
Throttle position sensor
EGR position sensor
Exhaust pressure sensor
Engine coolant temperature sensor
Crankshaft position sensor
Camshaft position sensor

When the ECM requires exhaust gas recirculation, it may command the EGR valve and adjust the EGR throttle to create the correct airflow and pressure conditions.

If the electrical signal in Circuit A becomes too high, the ECM may store P2142 and limit or disable part of the system.

What Does "Circuit A" Mean?

The letter "A" identifies a specific circuit or component within the manufacturer's control strategy.

It does not always mean:

The first physical wire
The first throttle
A specific cylinder
A specific engine bank

Circuit A may refer to:

A particular control wire
A specific actuator circuit
One control channel
One section of a multi-circuit component

The exact meaning must be confirmed using the vehicle's wiring diagram.

What Does "Circuit High" Mean?

A circuit high code generally means that the ECM is detecting a voltage that is above its expected operating range.

Possible examples include:

A control wire shorted to battery voltage
An actuator receiving incorrect power
A damaged wire contacting a positive circuit
An internal actuator fault
Incorrect reference voltage
A faulty ECM/PCM driver

It does not necessarily mean that the EGR throttle is producing excessive airflow.

Symptoms of P2142

Symptoms vary depending on the vehicle and the EGR throttle system design.

Check Engine Light

The Check Engine Light is the most common symptom.

Reduced Engine Power

Many vehicles may enter a reduced-power or limp-home mode.

Poor Acceleration

The vehicle may feel slow or unresponsive.

Engine Hesitation

The engine may hesitate when accelerating.

Poor Fuel Economy

Incorrect airflow control can reduce engine efficiency.

Increased Emissions

The EGR system may not operate correctly, increasing emissions.

Rough Engine Operation

Some engines may idle or operate unevenly.

Engine Surging

The engine may experience inconsistent power delivery.

Stalling

In some cases, abnormal throttle control can contribute to stalling.

Hard Starting

Depending on the system design, starting may become more difficult.

Additional Warning Messages

Some vehicles may display messages such as:

Reduced engine power
Engine fault
Emissions system fault
Service engine

Common Causes of P2142

Short to Battery Voltage

A short to battery voltage is one of the most important causes of a circuit-high fault.

A damaged wire may contact:

Battery power wiring
Ignition power
Another positive voltage source

Possible causes include:

Melted insulation
Chafed wiring
Incorrect wiring repair
Harness damage
Aftermarket electrical modifications

Damaged Wiring Harness

The EGR throttle harness may be exposed to:

High temperatures
Engine vibration
Oil contamination
Moisture
Chafing
Abrasion

Inspect for:

Melted insulation
Exposed conductors
Broken wires
Incorrect repairs
Heat damage

Faulty EGR Throttle Actuator

The EGR throttle actuator may develop an internal electrical failure.

Possible problems include:

Internal short circuit
Internal control failure
Motor fault
Damaged actuator electronics
Incorrect internal resistance

Corroded Electrical Connector

Corrosion can affect the electrical characteristics of the control circuit.

Look for:

Green corrosion
White deposits
Moisture
Oxidized terminals
Loose pins
Damaged connector housing

Loose or Damaged Terminals

A connector may appear correctly installed while a terminal inside is:

Loose
Bent
Pushed backward
Corroded
Damaged

Terminal tension should be checked where appropriate.

Incorrect Power Supply

The EGR throttle control system may receive power through a dedicated or shared electrical circuit.

Possible problems include:

Incorrect voltage supply
Damaged fuse-box terminal
Faulty relay
Power-distribution problem
Incorrect wiring repair

Incorrect Previous Repair

A previous engine or wiring repair may have introduced an electrical problem.

Possible causes include:

Wrong wire connection
Incorrect splice
Pinched harness
Reversed wiring
Incorrect connector installation

Aftermarket Modifications

Electrical modifications can interfere with the EGR throttle control system.

Potential causes include:

ECU modifications
Engine swaps
Modified wiring harness
Performance electronics
Emissions-system modifications
Incorrectly installed accessories

Mechanical EGR Throttle Problems

Carbon buildup can cause an EGR throttle plate to stick.

Possible symptoms include:

Poor airflow
Hesitation
Rough running
Reduced performance

However, carbon buildup alone does not normally cause a circuit-high electrical code.

A mechanical inspection may still be necessary if electrical tests are normal or additional airflow-related codes are present.

Faulty ECM/PCM

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

Wiring faults
Connector problems
Actuator failures
Power-supply faults

The ECM/PCM should only be suspected after the external circuit has been properly tested.

Vehicles Commonly Affected by P2142

P2142 can occur on various OBD-II vehicles equipped with electronically controlled EGR throttle or intake-air control systems.

Examples may include:

Ford F-Series
Ford Ranger
Ford Transit
Ford Explorer
Chevrolet Silverado
Chevrolet Colorado
GMC Sierra
GMC Canyon
Ram 1500
Ram 2500
Jeep Grand Cherokee
Jeep Wrangler
Volkswagen Touareg
Volkswagen Passat
Audi Q7
Audi A6
BMW X5
BMW 3 Series
Mercedes-Benz Sprinter
Mercedes-Benz E-Class
Nissan Navara
Nissan Pathfinder
Toyota Hilux
Toyota Land Cruiser
Toyota Tundra

This list is not exhaustive.

P2142 is more likely to be associated with vehicles using electronically controlled EGR and intake-air systems, particularly many modern diesel engines.

Important: The exact EGR throttle system varies significantly by engine. A specific vehicle may not use the same component layout as another model from the same manufacturer.

How Is P2142 Diagnosed?

The purpose of diagnosis is to determine why the EGR throttle control circuit voltage is higher than expected.

Check for Additional Trouble Codes

Perform a complete diagnostic scan.

Look for:

P2142
Other EGR codes
Throttle actuator codes
Intake-air control codes
Mass airflow codes
Manifold pressure codes
Battery-voltage codes
Communication codes

Related codes can help determine whether the problem is limited to the EGR throttle circuit.

Check Freeze-Frame Data

Review the conditions recorded when P2142 was stored.

Useful information includes:

Engine RPM
Vehicle speed
Engine load
Battery voltage
Coolant temperature
Throttle command
EGR command
EGR position

This can help determine when the circuit-high condition occurred.

Identify the Correct Circuit A

Use the vehicle-specific wiring diagram to identify:

EGR throttle actuator
Circuit A
Power supply
Ground
Control wires
Feedback circuits
Fuse
Relay
ECM/PCM terminals

Do not assume that Circuit A has the same configuration on all vehicles.

Inspect the EGR Throttle and Wiring

Perform a visual inspection of the component and harness.

Check for:

Broken wires
Melted insulation
Chafing
Oil contamination
Loose connectors
Corrosion
Incorrect repairs

Pay close attention to wiring located near hot exhaust components.

Measure Circuit Voltage

Measure the appropriate circuit voltage according to manufacturer procedures.

Compare the measured voltage with the expected specification.

If the voltage is too high, trace the circuit toward:

Battery power
Ignition power
Fuse
Relay
Power-distribution system
Wiring harness
Actuator
ECM/PCM

Check for a Short to Battery Voltage

With the circuit safely isolated according to manufacturer procedures, check for an unintended connection to a positive voltage source.

This is especially important for a circuit-high code.

Inspect the Electrical Connector

Check for:

Bent terminals
Corrosion
Moisture
Loose pins
Damaged locking tabs
Backed-out terminals

Test the EGR Throttle Actuator

Depending on the system design, test:

Power supply
Ground
Motor resistance
Control circuit
Feedback signal
Actuator response

Compare all measurements with manufacturer specifications.

Check for Excessive Resistance

Perform voltage-drop testing on:

Power circuits
Ground circuits
Connector terminals
Relay contacts

High resistance can cause unusual control behavior.

Inspect Power and Ground Circuits

Verify that the EGR throttle actuator receives:

Correct power
Reliable ground
Correct control signal

A poor ground or incorrect power supply can produce misleading circuit readings.

Check Throttle Position Feedback

If the EGR throttle contains a position sensor, verify:

Reference voltage
Sensor ground
Feedback signal
Signal response

A faulty position circuit may cause the ECM to detect abnormal operation.

Inspect for Carbon Buildup

If the electrical circuit is operating correctly, inspect the EGR throttle for:

Carbon deposits
Sticking throttle plate
Restricted movement
Mechanical damage

This is especially important when performance symptoms are present.

Check ECM/PCM Power and Grounds

Verify:

Battery voltage
Ignition power
ECM/PCM grounds
Related reference-voltage circuits

Check for Aftermarket Modifications

Inspect modifications involving:

ECU tuning
Engine wiring
EGR systems
Engine swaps
Performance electronics

Incorrect modifications can affect the EGR throttle circuit.

How to Fix P2142

The correct repair depends on the fault identified during diagnosis.

Repair a Short to Battery Voltage

If the control circuit is shorted to battery voltage, repair the damaged wiring and restore the correct harness routing.

Repair Damaged Wiring

Repair or replace wiring affected by:

Heat
Chafing
Corrosion
Vibration
Oil contamination

Repair or Replace Damaged Connectors

Replace damaged connector housings or terminals when necessary.

Ensure proper terminal tension.

Replace a Faulty EGR Throttle Actuator

If testing confirms an internal actuator failure, replace the EGR throttle or related intake-air control component.

Repair Power-Supply Problems

Repair:

Fuse connections
Relay circuits
Power-distribution wiring
Incorrect voltage supplies

Repair Ground Problems

Restore proper:

Engine grounds
Chassis grounds
Actuator grounds
ECM/PCM grounds

Clean the EGR Throttle

If carbon buildup is causing mechanical sticking, clean the component according to manufacturer procedures.

Do not damage electronic sensors or actuator components during cleaning.

Correct Previous Wiring Repairs

Repair incorrect splices and restore the original wiring configuration.

Correct Aftermarket Modifications

Restore modified EGR throttle wiring to the correct manufacturer configuration when modifications are responsible for the fault.

Repair or Replace the ECM/PCM

The ECM/PCM should only be considered after the wiring, actuator, connectors, power supply, ground circuits, and related sensors have been thoroughly tested.

What Happens If P2142 Is Ignored?

Ignoring P2142 can result in continued engine and emissions problems.

Possible consequences include:

Reduced engine power
Poor acceleration
Increased emissions
Failed emissions inspection
Poor fuel economy
Engine hesitation
Rough running
Limp mode
Additional EGR-related trouble codes

If the electrical fault is caused by damaged wiring, continued operation may also lead to further harness damage.

Can You Drive With P2142?

Driving with P2142 may be possible, but the vehicle should be diagnosed promptly.

A short drive may be possible if:

The engine runs smoothly.
There is no major loss of power.
The vehicle is not stalling.
The Check Engine Light is not flashing.
No serious warning messages are displayed.

Avoid driving if you experience:

Severe loss of power
Repeated stalling
Severe engine hesitation
Flashing Check Engine Light
Multiple warning lights
Strong electrical smell or visible wiring damage

Is P2142 a Serious Code?

P2142 is generally considered a moderate-severity diagnostic trouble code.

The code does not necessarily indicate that the engine is internally damaged.

However, an EGR throttle control circuit fault can affect:

Engine airflow
EGR operation
Emissions
Engine performance
Fuel efficiency

If the circuit-high condition is caused by a short to battery voltage, the electrical problem should be repaired promptly.

How to Prevent P2142

Recommended maintenance practices include:

Inspect engine wiring regularly.
Keep wiring away from hot exhaust components.
Repair damaged wiring promptly.
Keep electrical connectors clean and dry.
Maintain engine and chassis grounds.
Address charging-system problems quickly.
Inspect the EGR throttle for carbon buildup when appropriate.
Use correct replacement components.
Secure wiring harnesses properly.
Avoid poorly designed electrical modifications.
Inspect wiring after major engine repairs.
Do not ignore Check Engine Light warnings.

P2142 vs. Related Codes

Code	General Description
P2142	EGR Throttle Control Circuit "A" High
P2143	EGR Vent Control Circuit/Open
P2144	EGR Vent Control Circuit Low
P2145	EGR Vent Control Circuit High
P2146	Fuel Injector Group "A" Supply Voltage Circuit/Open
P2147	Fuel Injector Group "A" Supply Voltage Circuit Low
P2148	Fuel Injector Group "A" Supply Voltage Circuit High

The important difference is that P2142 relates to the EGR throttle control circuit, while P2143 through P2145 relate to the EGR vent control circuit.

Final Thoughts

The P2142 Exhaust Gas Recirculation (EGR) Throttle Control Circuit "A" High diagnostic trouble code indicates that the ECM/PCM has detected a higher-than-expected electrical signal in the EGR throttle control circuit identified as "A."

Common causes include:

Short to battery voltage
Damaged wiring
Faulty EGR throttle actuator
Corroded connectors
Loose or damaged terminals
Incorrect power supply
Faulty relay or power-distribution circuit
Incorrect wiring repairs
Aftermarket modifications
ECM/PCM faults

The correct diagnosis starts with checking related codes and freeze-frame data, identifying the exact Circuit A using the vehicle's wiring diagram, inspecting the wiring and connectors, measuring circuit voltage, checking for a short to battery voltage, and testing the EGR throttle actuator.

If electrical testing does not reveal a fault, the EGR throttle and intake-air passages should be inspected for carbon buildup or mechanical sticking.

P2142 does not automatically mean that the EGR throttle assembly needs replacement. A shorted wire, damaged connector, incorrect power supply, or faulty electrical control circuit can produce the same code.

Finding the actual source of the high electrical signal is essential for repairing P2142 correctly and restoring proper airflow, EGR operation, engine performance, and emissions control.