P2639 OBD-II Trouble Code: Torque Management Feedback Signal A Low

P2639 code definition

This DTC indicates Torque Management Feedback Signal A Low.

What the P2639 code means

This code sets when one of the components involved in torque management sends a signal to one of the supporting control modules which falls outside of the expected voltage range. These controllers may include the transmission control module (TCM), the antilock brake control module, the body control module, the fuel injection control module, or a range of other modules which monitor the vehicle’s systems. The letter A refers to a specific area of the involved circuitry.

What causes the P2639 code?

One of the most common culprits in this fault is a driver problem within the PCM or other supporting controller. Another frequent issue is a bad connection in the circuitry. Other possible causes may include:

• An open or short due to damaged CAN bus (the complex network of harnesses and wires connecting various control modules together) wires or connectors
• A loose ground strap or damaged ground wire to the involved control module
• A faulty CAN bus harness

What are the symptoms of the P2639 code?

The Service Engine Soon light may come on, but it may take up to eight drive cycles for this to occur. Other signs could include harsh shifting, poor drivability, engine stalls, rough idling, sluggish acceleration, and/or reduced fuel efficiency. In addition, if the Check Engine light has not illuminated yet, the DTC may show as “pending”.

How does a mechanic diagnose the P2639 code?

Accurate diagnosis of this condition may require:

• Scanning the vehicle to check for any concurrent codes and to record freeze frame data
• Clearing the DTCs to see if they return (in an attempt to diagnose an intermittent condition)
• Using a specialized CAN scanner to detect control module operation and pin values
• Visually inspecting all involved wiring and connectors to check for damage or loose connections
• Testing for continuity to the battery ground
• Testing of the control modules related to the torque management feedback signal

Common mistakes when diagnosing the P2639 code

The most common error in diagnosing this condition is failure to follow the recommended procedure of diagnosing and repairing other DTCs present with the torque converter management signal fault. Transmission or drivability codes that may accompany the controller communication fault include lean exhaust, fuel injector, engine misfire, or other codes.

How serious is the P2639 code?

While this fault may not cause serious fallout, it can impair the way the vehicle runs, potentially causing you to stall out at an inconvenient time. Rough shifting may also occur, affecting drivability, as well as decreased fuel efficiency. It’s best to have this DTC diagnosed and repaired promptly.

What repairs can fix the P2639 code?

Your technician may perform the following repairs:

• Verifying the set code and any other faults that are present, and recording freeze frame data
• Clearing the data from the vehicle’s computer to see if the problem returns (otherwise an intermittent condition may exist)
• Repairing faulty wiring and connections involved in the relevant control modules
• Repairing any problems in the complex collection of harnesses and connectors which make up the CAN bus network
• Replacing any faulty control modules

Additional comments for consideration regarding the P2639 code

This diagnosis and repair could involve extensive procedures to find the source of the fault, and often requires specialized equipment like a CAN bus scanner in order to pinpoint problems without painstaking hours of examination. In addition, some vehicle models may contain up to 18 different control modules, making it a challenging undertaking to identify the source of the problem.

For these reasons, it’s often most economical and efficient to leave P2639 repair to a qualified technician.

Need help with a P2639 code?

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