P2636 – Fuel Pump ‘B’ Low Flow / Performance

P2636 Possible Causes

  • Faulty fuel pump relay
  • Defective fuel pump
  • Fuel pump wiring harness is open or shorted
  • Poor electrical connection in the fuel pump circuit
  • Faulty fuel pump control module (if applicable)

How to Fix Code P2636

Check the “Possible Causes” listed above. Visually inspect the wiring harness and related connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Illuminated engine light (or service engine soon warning light)

P2636 Meaning

The Engine Control Module (ECM) monitors the fuel pump control circuit. The ECM sets the OBDII code when the fuel pump control circuit is outside factory specifications.

P2637 – Torque Management Return Signal “A

P2637 Possible Causes

  • Faulty Engine Control Module (ECM)
  • Faulty Transmission Control Module (TCM)
  • Engine Control Module (ECM) software update
  • Transmission Control Module (TCM) software update
  • Engine Control Module (ECM) harness is open or shorted
  • Poor electrical connection in Engine Control Module (ECM) circuit

How to Fix Code P2637

Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Illuminated engine light (or service engine soon warning light)

P2637 Meaning

To improve shift feel, the Transmission Control Module (TCM) may request that the Engine Control Module (ECM) reduce engine torque during shift events. When such a request is received, the ECM responds by retarding base ignition timing and notifying the TCM that the request was successful. If the ECM is unable to comply with the request, the ECM sends a message to the TCM indicating that the request failed.

The torque reduction request is sent to the ECM via a communication network called CAN (Controller Area Network). Two circuits are used to communicate CAN data between the ECM and TCM.

A fault in the CAN will not cause the ECM to set Diagnostic Trouble Codes (DTCs). If a CAN fault occurs, other DTCs will be set before this code.

The ECM sets the OBDII code when the TCM receives a torque reduction failure message from the ECM.

P2638 – Torque Management Feedback Signal “A” Range/Performance

P2638 Possible Causes

  • Faulty Engine Control Module (ECM)
  • Faulty Transmission Control Module (TCM)
  • Engine Control Module (ECM) software update
  • Transmission Control Module (TCM) software update
  • Engine Control Module (ECM) harness is open or shorted
  • Poor electrical connection in Engine Control Module (ECM) circuit

How to Fix Code P2638

Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Illuminated engine light (or service engine soon warning light)

P2638 Meaning

To improve shift feel, the Transmission Control Module (TCM) may request that the Engine Control Module (ECM) reduce engine torque during shift events. When such a request is received, the ECM responds by retarding base ignition timing and notifying the TCM that the request was successful. If the ECM is unable to comply with the request, the ECM sends a message to the TCM indicating that the request failed.

The torque reduction request is sent to the ECM via a communication network called CAN (Controller Area Network). Two circuits are used to communicate CAN data between the ECM and TCM.

A fault in the CAN will not cause the ECM to set diagnostic trouble codes (DTCs). If a CAN fault occurs, other DTCs will be set before this code.

The ECM sets the OBDII code when the TCM receives a torque reduction failure message from the ECM.

P2639 – Low Torque Management “A” Return Signal

P2639 Possible Causes

  • Faulty Engine Control Module (ECM)
  • Faulty Transmission Control Module (TCM)
  • Engine Control Module (ECM) software update
  • Transmission Control Module (TCM) software update
  • Engine Control Module (ECM) harness is open or shorted
  • Poor electrical connection in Engine Control Module (ECM) circuit

How to Fix Code P2639

Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Illuminated engine light (or service engine soon warning light)

P2639 Meaning

To improve shift feel, the Transmission Control Module (TCM) may request that the Engine Control Module (ECM) reduce engine torque during shift events. When such a request is received, the ECM responds by retarding base ignition timing and notifying the TCM that the request was successful. If the ECM is unable to comply with the request, the ECM sends a message to the TCM indicating that the request failed.

The torque reduction request is sent to the ECM via a communication network called CAN (Controller Area Network). Two circuits are used to communicate CAN data between the ECM and TCM.

A fault in the CAN will not cause the ECM to set diagnostic trouble codes (DTCs). If a CAN fault occurs, other DTCs will be set before this code.

The ECM sets the OBDII code when the TCM receives a torque reduction failure message from the ECM.

P2640 – High Torque Management “A” Return Signal

P2640 Possible Causes

  • Faulty Engine Control Module (ECM)
  • Faulty Transmission Control Module (TCM)
  • Engine Control Module (ECM) software update
  • Transmission Control Module (TCM) software update
  • Engine Control Module (ECM) harness is open or shorted
  • Poor electrical connection in Engine Control Module (ECM) circuit

How to Fix Code P2640

Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Engine Light On (or Service Engine Soon Warning Light)

P2640 Meaning

To improve shift feel, the Transmission Control Module (TCM) may request that the Engine Control Module (ECM) reduce engine torque during shift events. When such a request is received, the ECM responds by retarding base ignition timing and notifying the TCM that the request was successful. If the ECM is unable to comply with the request, the ECM sends the TCM a message indicating the request failed.

The torque reduction request is sent to the ECM via a communication network called CAN (Controller Area Network). Two circuits are used to communicate CAN data between the ECM and TCM.

A fault in the CAN will not cause the ECM to set Diagnostic Trouble Codes (DTCs). If a CAN fault occurs, other DTCs will be set before this code.

The ECM sets the OBDII code when the TCM receives a torque reduction failure message from the ECM.

P2641 – Torque Management Return Signal “B

P2641 Possible Causes

  • Faulty Engine Control Module (ECM)
  • Faulty Transmission Control Module (TCM)
  • Engine Control Module (ECM) software update
  • Transmission Control Module (TCM) software update
  • Engine Control Module (ECM) harness is open or shorted
  • Poor electrical connection in Engine Control Module (ECM) circuit

How to Fix Code P2641

Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Illuminated engine light (or service engine soon warning light)

P2641 Meaning

To improve shift feel, the Transmission Control Module (TCM) may request that the Engine Control Module (ECM) reduce engine torque during shift events. When such a request is received, the ECM responds by retarding base ignition timing and notifying the TCM that the request was successful. If the ECM is unable to comply with the request, the ECM sends the TCM a message indicating the request failed.

The torque reduction request is sent to the ECM via a communication network called CAN (Controller Area Network). Two circuits are used to communicate CAN data between the ECM and TCM.

A fault in the CAN will not cause the ECM to set Diagnostic Trouble Codes (DTCs). If a CAN fault occurs, other DTCs will be set before this code.

The ECM sets the OBDII code when the TCM receives a torque reduction failure message from the ECM.

P2642 – Torque Management “B” Feedback Signal Range/Performance

P2642 Possible Causes

  • Faulty Engine Control Module (ECM)
  • Faulty Transmission Control Module (TCM)
  • Engine Control Module (ECM) software update
  • Transmission Control Module (TCM) software update
  • Engine Control Module (ECM) harness is open or shorted
  • Poor electrical connection in Engine Control Module (ECM) circuit

How to Fix Code P2642

Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Illuminated engine light (or service engine soon warning light)

P2642 Meaning

To improve shift feel, the Transmission Control Module (TCM) may request that the Engine Control Module (ECM) reduce engine torque during shift events. When such a request is received, the ECM responds by retarding base ignition timing and notifying the TCM that the request was successful. If the ECM is unable to comply with the request, the ECM sends the TCM a message indicating the request failed.

The torque reduction request is sent to the ECM via a communication network called CAN (Controller Area Network). Two circuits are used to communicate CAN data between the ECM and TCM.

A fault in the CAN will not cause the ECM to set diagnostic trouble codes (DTCs). If a CAN fault occurs, other DTCs will be set before this code.

The ECM sets the OBDII code when the TCM receives a torque reduction failure message from the ECM.

P2643 – Low Torque Management Return Signal “B

P2643 Possible Causes

  • Faulty Engine Control Module (ECM)
  • Faulty Transmission Control Module (TCM)
  • Engine Control Module (ECM) software update
  • Transmission Control Module (TCM) software update
  • Engine Control Module (ECM) harness is open or shorted
  • Poor electrical connection in Engine Control Module (ECM) circuit

How to Fix Code P2643

Check the “Possible Causes” listed above. Visually inspect the wiring harness and related connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Illuminated engine light (or service engine soon warning light)

P2643 Meaning

To improve shift feel, the Transmission Control Module (TCM) may request that the Engine Control Module (ECM) reduce engine torque during shift events. When such a request is received, the ECM responds by retarding base ignition timing and notifying the TCM that the request was successful. If the ECM is unable to comply with the request, the ECM sends the TCM a message indicating that the request failed.

The torque reduction request is sent to the ECM via a communication network called CAN (Controller Area Network). Two circuits are used to communicate CAN data between the ECM and TCM.

A fault in the CAN will not cause the ECM to set Diagnostic Trouble Codes (DTC). If a CAN fault occurs, other DTCs will be set before this code.

The ECM sets the OBDII code when the TCM receives a torque reduction failure message from the ECM.

P2644 – High Torque Management Return Signal “B

P2644 Possible Causes

  • Faulty Engine Control Module (ECM)
  • Faulty Transmission Control Module (TCM)
  • Engine Control Module (ECM) software update
  • Transmission Control Module (TCM) software update
  • Engine Control Module (ECM) harness is open or shorted
  • Poor electrical connection in Engine Control Module (ECM) circuit

How to Fix Code P2644

Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Illuminated engine light (or service engine soon warning light)

P2644 Meaning

To improve shift feel, the Transmission Control Module (TCM) may request that the Engine Control Module (ECM) reduce engine torque during shift events. When such a request is received, the ECM responds by retarding base ignition timing and notifying the TCM that the request was successful. If the ECM is unable to comply with the request, the ECM sends the TCM a message indicating the request failed.

The torque reduction request is sent to the ECM via a communication network called CAN (Controller Area Network). Two circuits are used to communicate CAN data between the ECM and TCM.

A fault in the CAN will not cause the ECM to set diagnostic trouble codes (DTCs). If a CAN fault occurs, other DTCs will be set before this code.

The ECM sets the OBDII code when the TCM receives a torque reduction failure message from the ECM.

P2645 – Rocker Actuator Control Circuit ‘A’ / Bank 1 Open

P2645 Possible Causes

  • Low or overfilled engine oil
  • Incorrect engine oil type
  • Faulty rocker arm actuator ‘A’
  • Rocker arm actuator ‘A’ circuit is open or shorted
  • Poor electrical connection in rocker arm actuator ‘A’ circuit

How to Fix Code P2645

Check the “Possible Causes” listed above. Visually inspect the wiring harness and related connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Illuminated engine light (or service engine soon warning light)

P2645 Meaning

The Engine Control Module (ECM) commands the rocker arm actuator to control the hydraulic oil circuit. Oil flows through the rocker arm actuator to the variable valve timing system to adjust engine valve timing. The Variable Valve Timing (VVT) system is used to improve engine performance, fuel economy, or emissions. The ECM monitors the rocker arm actuator circuit and sets the OBDII code when the rocker arm actuator ‘A’ circuit is outside factory specifications.