Code Severity and Symptoms

The severity of this code is moderate but will progress if not corrected in a timely manner. Symptoms of a P2629 fault code may include:

• Poor performance that worsens
• Engine running lean
• Engine running rich
• Engine light illuminated
• Smoke from the exhaust pipe
• Increased fuel consumption

Common Causes of a P2629 Code

Possible causes of this code may include:

• Faulty O2 sensor
• Carbon buildup on the O2 sensor
• Blown fuse (if applicable)
• Fuel pressure too high
• Fuel pressure too low
• Engine vacuum leak
• Excessive exhaust leak
• Corroded or damaged connector
• Faulty or damaged wiring
• Faulty PCM

P2629 Diagnostic and Repair Procedures

Check TSBs

The first step in troubleshooting any malfunction is to search for Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and powertrain. In some circumstances, this can save significant time in the long run by pointing you in the right direction.

The second step is to locate the pre-catalytic converter O2 sensor. Perform a thorough visual inspection to check the associated wiring for obvious defects such as scraping, rubbing, bare wires, or burns. Then, check the connector for security, corrosion, and damaged pins. With the engine running, the visual inspection should include identifying possible exhaust leaks. Based on fuel consumption and fuel pressure tests, engine operation adjustments may be recommended. You should consult specific technical data to determine this requirement.

Advanced Steps

Advanced steps become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and vehicle-specific technical references. Voltage requirements will be highly dependent on the specific vehicle’s year, model, and engine.

Voltage Checks

When the fuel mixture is balanced at approximately 14.7 to 1, which is normal for most engines to achieve optimal performance, the sensor will read about 0.45 volts. An oxygen sensor typically generates up to about 0.9 volts when the fuel mixture is rich and there is unburned oxygen in the exhaust gases. When the mixture is lean, the sensor’s output voltage will drop to about 0.1 volt.

If this process identifies the absence of a power source or ground, continuity tests may be required to check the wiring integrity. Continuity tests should always be performed with the power disconnected from the circuit, and normal readings should be 0 ohms of resistance unless otherwise indicated by technical data. Resistance or lack of continuity indicates faulty wiring that is open or short-circuited and must be repaired or replaced.

Common Repairs

• Replacing or cleaning the O2 sensor
• Replacing a blown fuse (if applicable)
• Adjusting fuel pressure
• Repairing engine vacuum leaks
• Repairing exhaust leaks
• Cleaning connector corrosion
• Repairing or replacing wiring
• PCM replacement

I hope the information in this article has helped guide you in the right direction to correct the issue with your O2 sensor pump current compensation circuit. This article is strictly informational, and the technical data and service bulletins specific to your vehicle should always take priority.

How Severe is This DTC?

This specific fault code is a moderately serious issue for your vehicle. You can still use your vehicle despite the problem. However, it is strongly advised against doing so, as you risk intermittently supplying fuel to the engine, and an erratic or fluctuating fuel mixture could permanently cause severe engine damage.

What Are Some Symptoms of the Code?

Symptoms of a P2632 fault code may include:

• Check engine light is on
• Engine does not start
• Engine misfires/stalling
• Engine starts but dies
• Fuel economy is reduced
• Engine cranks but does not start
• Engine dies when reaching operating temperature

Note: It is always possible that the issue is not resolved, even if the check engine light does not come on immediately. Always ensure your vehicle has undergone a few driving cycles, i.e., drive the car for a week; if the CEL (check engine light) is not on by the end, the problem is most likely resolved.

What Are Some Common Causes of the Code?

Causes

of this code may include:

• Issues with the fuel pump itself
• Cut or damaged ground wire in the control module
• Unsecured ground strap in the control module
• Open, shorted, or corroded wiring in the CAN bus
• A faulty CAN bus
• Unsecured harness and wires causing chafing or broken circuits
• High resistance in the circuit (e.g., melted/corroded connectors, internal wire corrosion)

What Are the Troubleshooting Steps for P2632?

The first thing I recommend doing is searching for Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and powertrain. In some circumstances, this can save you a lot of time in the long run by pointing you in the right direction.

Basic Step 1

You should always scan and test each module immediately using an OBD-II scanner to get a good idea of the overall electrical condition of your vehicle and its modules. You should also always perform a visual inspection of connectors and wiring in case something is obviously damaged, in which case it should be repaired or replaced. Often, these are located under the vehicle near the fuel tank. They are sensitive to road debris and the elements, so pay close attention to their condition.

Basic Step 2

When dealing with a component with its own module (e.g., fuel pump module, etc.), you need to examine the ground circuits. You can do this using a separate battery ground. Sometimes, you can do this easily using an auxiliary ground cable. If your problem is resolved with the auxiliary ground attached but returns when the OEM ground is used, it means your ground cable is the source of the issue and needs to be repaired or replaced. Grounds should always be carefully inspected for corroded connections, terminals, pins, etc., that could be causing circuit resistance. A good sign of excessive corrosion is a green ring around the connector attached to the positive battery terminal. If this is present, remove the terminal and clean all contact points, the face of the connector, and the terminal/stud.

Basic Step 3

Since the cause of the P2632 code can be an open circuit, you need to identify the circuit using an electrical wiring diagram in your service manual. Once identified, you can individually trace the fuel pump control wire A to see if there are any obvious breaks in the wire. Repair as necessary by soldering the wire (which I recommend) or using butt connectors with heat shrink to insulate it from the elements. Using your multimeter, you can measure the resistance between the circuit connectors to locate the short/open circuit location. A power probe-style tool is highly recommended here if there is a fault somewhere within the entire circuit.

I hope this article has been helpful in guiding you in the right direction to diagnose the issue with your fuel pump control circuit fault code. This article is strictly informational, and technical data and service bulletins specific to your vehicle should always take priority.

How severe is this DTC?

This particular fault code is a moderately serious issue for your vehicle. You can still use your vehicle despite the problem. However, it is strongly advised not to do so, as you risk intermittently supplying fuel to the engine, and an erratic or fluctuating fuel mixture could permanently cause severe engine damage.

What are some of the symptoms of the code?

Symptoms of a P2633 fault code may include:

• Check engine light is on
• Engine does not start
• Engine misfires/stalling
• Engine starts but dies
• Fuel economy is reduced
• Engine cranks but does not start
• Engine dies when reaching operating temperature

Note: It is always possible that the problem is not resolved, even if the check engine light does not come on immediately. Always ensure your vehicle has undergone a few driving cycles, i.e., drive the car for a week; if the CEL (check engine light) is not on by the end, the issue is most likely resolved.

What are some common causes of the code?

Causes

of this code may include:

• Issues with the fuel pump itself
• Cut or damaged ground wire in the device control module
• Unsecured ground strap in the control module
• Open, shorted, or corroded wiring in the CAN bus
• A faulty CAN bus
• Unsecured harness and wires causing chafing or a broken circuit
• High resistance in the circuit (e.g., melted/corroded connectors, internal wire corrosion)

What are the troubleshooting steps for P2633?

The first thing I recommend doing is searching for Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and powertrain. In some cases, this can save you a lot of time in the long run by pointing you in the right direction.

Basic Step 1

You should always scan and immediately test each module using an OBD-II scanner to get a good idea of the overall electrical state of your vehicle and its modules. You should also always perform a visual inspection of connectors and wiring in case something is obviously damaged, in which case it should be repaired or replaced. Often, these are located under the vehicle near the fuel tank. They are sensitive to road debris and the elements, so pay close attention to their condition.

Basic Step 2

When dealing with a component that has its own module (e.g., fuel pump module, etc.), you need to check the ground circuits. You can do this using a separate battery ground. Sometimes, you can do this easily with an auxiliary ground cable. If your issue is resolved with the auxiliary ground attached but returns when the OEM ground is used, it means your ground cable is the source of the problem and needs to be repaired or replaced. Grounds should always be carefully inspected for corroded connections, terminals, pins, etc., that could be causing circuit resistance. A good sign of excessive corrosion is a green ring around the connector attached to the positive battery terminal. If this is present, remove the terminal and clean all contact points, the face of the connector, and the terminal/stud.

Basic Step 3

Since the cause of the P2633 code could be an open circuit, you need to identify the circuit using an electrical wiring diagram from your service manual. Once identified, you can individually trace the fuel pump control wire A to see if there are any obvious breaks in the wire. Repair as necessary by soldering the wire (which I recommend) or using butt connectors with heat shrink to insulate it from the elements. Using your multimeter, you can measure the resistance between the circuit connectors to locate the short/open circuit location. A power probe-style tool is highly recommended here if there is a fault somewhere within the entire circuit.

I hope this article has been helpful in guiding you in the right direction to diagnose the issue with your fuel pump control circuit fault code. This article is strictly informational, and technical data and service bulletins specific to your vehicle should always take priority.

How Severe Is This DTC?

This specific fault code is a moderately serious issue for your vehicle. You can still use your vehicle despite the problem. However, it is strongly advised against doing so, as you risk intermittently supplying fuel to the engine, and an erratic or fluctuating fuel mixture could permanently cause severe engine damage.

What Are Some Symptoms of the Code?

Symptoms of a P2634 fault code may include:

• Check engine light is on
• Engine does not start
• Engine misfires/stalling
• Engine starts but dies
• Fuel economy is reduced
• Engine cranks but does not start
• Engine dies when reaching operating temperature

Note: It is always possible that the issue is not resolved, even if the check engine light does not come on immediately. Always ensure your vehicle has undergone a few driving cycles, i.e., drive the car for a week; if the CEL (check engine light) is not on by the end, the problem is most likely resolved.

What Are Some Common Causes of the Code?

Causes

of this code may include:

• Issues with the fuel pump itself
• Cut or damaged ground wire in the control module
• Unsecured ground strap in the control module
• Open, shorted, or corroded wiring in the CAN bus
• A faulty CAN bus
• Unsecured harness and wires causing chafing or a broken circuit
• High resistance in the circuit (e.g., melted/corroded connectors, internal wire corrosion)

What Are the Troubleshooting Steps for P2634?

The first thing I recommend doing is searching for Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and powertrain. In some cases, this can save you a lot of time in the long run by pointing you in the right direction.

Basic Step 1

You should always scan and test each module immediately using an OBD-II scanner to get a good idea of your vehicle’s overall electrical condition and its modules. You should also always perform a visual inspection of connectors and wiring in case something is obviously damaged, in which case it should be repaired or replaced. Often, these are located under the vehicle near the fuel tank. They are sensitive to road debris and the elements, so pay close attention to their condition.

Basic Step 2

When dealing with a component that has its own module (e.g., fuel pump module, etc.), you need to check the ground circuits. You can do this using a separate battery ground. Sometimes, you can do this easily using an auxiliary ground cable. If your issue is resolved with the auxiliary ground attached but returns when the OEM ground is used, it means your ground cable is the source of the problem and needs to be repaired or replaced. Grounds should always be carefully inspected for corroded connections, terminals, pins, etc., that could be causing circuit resistance. A good sign of excessive corrosion is a green ring around the connector attached to the battery’s positive terminal. If this is present, remove the terminal and clean all contact points, the connector face, and the terminal/stud.

Basic Step 3

Since the cause of the P2634 code could be an open circuit, you need to identify the circuit using an electrical wiring diagram from your service manual. Once identified, you can individually trace the fuel pump control wire A to see if there are any obvious breaks in the wire. Repair as necessary by soldering the wire (which I recommend) or using butt connectors with heat shrink to insulate it from the elements. Using your multimeter, you can measure the resistance between the circuit connectors to locate the short/open circuit’s position. A power probe-style tool is highly recommended here if there is a fault somewhere within the entire circuit.

I hope this article has been helpful in guiding you in the right direction to diagnose the issue with your fuel pump control circuit fault code. This article is strictly informational, and technical data and service bulletins specific to your vehicle should always take priority.

What Does Code P2635 Mean?

Code P2635 indicates that the engine control module (ECM) has detected a malfunction in the fuel pump control circuit. This means the pump is not operating as expected, which can affect the engine’s fuel supply.

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Possible Symptoms:

• Check engine light illuminated on the dashboard
• Engine may have difficulty starting or run irregularly
• Loss of power or possible stalling

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Possible Causes:

• Fuel pump failure
• Fuel pump relay defective
• Damaged wiring (cut wires, short circuit, poor connection)
• Loose or corroded connectors
• Fuel pump control module faulty (if present on the vehicle)

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How to Fix the Problem?

1. Visually inspect the cables and connectors around the fuel pump. Look for cut wires, broken, or oxidized connectors.
2. Test the fuel pump relay – this is often a common cause of failure.
3. Check the pump itself, especially if the vehicle has difficulty starting or engine cutouts.
4. If the vehicle is equipped with one, also check the fuel pump control module.

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🔧 Tip: This type of failure can lead to loss of performance or starting problems. It is recommended to have the vehicle diagnosed quickly, especially if symptoms worsen.

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 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 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 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 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.