P2638 OBD-II Trouble Code: Torque Management Feedback Signal 'A' Range/Performance

P2638 code definition

If the Powertrain Control Module (PCM) stores a P2638 trouble code, it indicates that a signal malfunction has been detected in the PCM or one of the other support modules, dealing specifically with the torque management feedback.

Related trouble codes include a P2639, P2640, P2641, P2642, P2643, or P2644 code.

What the P2638 code means

A torque management feedback signal malfunction is the common cause of a P2638 trouble code. In addition to the vehicle PCM, a P2638 trouble code can also originate from problems in various related control modules, including:

• The transmission control module
• The body control module
• The antilock brake control module
• The instrument panel control module
• The fuel injection control module
• The turbo control module
• The anti-theft module
• The cruise control module
• The traction control module
• The proximity alert module
• The climate control module

What causes the P2638 code?

Contrary to other types of trouble code causes, a P2638 trouble code is usually caused by a defective driver in the PCM, or a related control module, as well as a possible loose electrical connection. Some other causes include shorted or corroded wiring and connectors within the Controller Area Network (CAN) Bus harness, a defective CAN Bus, a broken ground wire, and a loose ground strap on one of the control modules.

What are the symptoms of the P2638 code?

Symptoms of a P2638 trouble code include engine stalling or rough idling, lessened fuel economy, and harsh shifting. In addition to a stored trouble code and illuminated Check Engine light, the PCM might show the trouble code as pending with no lit Check Engine light.

How does a mechanic diagnose the P2638 code?

The equipment needed by a mechanic to successfully diagnose a P2638 trouble code is an advanced scanner and a digital volt/ohmmeter. In addition to the needed equipment, the mechanic should also perform the following steps while diagnosing the problem.

• Begin by visually inspecting the wiring, connector, and other components associated with the torque management feedback signal.

• Retest the system after repairing all wiring, connectors, and components.

• If everything appears normal, connect the advanced scanner to the diagnostic connector and download the freeze frame data and any stored codes.

• Clear the code and test drive the vehicle to see if the problem returns.

• In addition to an advanced scanner, a mechanic can use a specialized scanner to pinpoint the general area of the problem quicker.

• The mechanic can also use a specialized diagnostic CAN scanner to more easily show the pin values and control module operation. Otherwise, the process can be time consuming and cost prohibitive for the mechanic.

• In addition to the control modules themselves, the mechanic should check the ground circuits for continuity with the ground of the battery.

• The mechanic should likewise look for any loose connectors while diagnosing a P2638 trouble code, as this is a common cause of such a code.

• The mechanic should compare any finding with the manufacturer's referenced values before attempting any repairs.

• Once the mechanic has made all the necessary repairs, they should clear the code and retest the system to see if the code returns.

Common mistakes when diagnosing the P2638 code

By not following the order that any codes were stored when diagnosing a P2638 trouble code can lead to a misdiagnosis on the mechanic's part. This misdiagnosis can lead to the replacement or repair of parts not associated with the trouble code being stored and the Check Engine light being lit in the first place. The resulting repair would not fix the problem at hand, with the code more than likely returning.

How serious is the P2638 code?

Not fixing a P2638 trouble code can lead to the fuel mileage of the vehicle worsening, as well as the engine idling rough and stalling. Another common problem with a P2638 trouble code is harsh shifting from the transmission.

What repairs can fix the P2638 code?

Once the mechanic has diagnosed the P2638 trouble code, they should attempt to repair the problem and clear the code by performing the following steps:

• Repair any faulty or damaged wiring, connectors, and components
• Make sure that all connections are secure before retesting the system

Additional comments for consideration regarding the P2638 code

Before diagnosing a P2638 trouble code, install a memory-saving device to keep from having to reprogram the PCM and related control modules following a potential loss of memory during the diagnostic process.

Need help with a P2638 code?

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