P2550 - OBD Trouble Code

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Error code P2550? Don’t know what to do about it? Well, Parts Avatar is at your service! Here’s everything you need to know about the error code P2550. One can observe that in order to improvise the shift feel, the transmission control module (TCM) requests the engine control module (ECM) to decrease engine torque during shift events. The ECM responds accordingly by retarding the base ignition timing and updating the TCM about the successful completion of the request, when such requests are made. When the request is not completed by the ECM, the TCM receives a message by the ECM about the unsuccessful request immediately.

Through the controller area network (CAN, a communication network), the torque reduction request is sent to the ECM. In order to communicate the CAN data between the ECM and the TCM, two circuits are used. Also, it should be noted that a failure in the CAN does not cause the ECM to store the diagnostic trouble code (DTC). Other DTCs are stored before the code P2550, if there is a CAN fault recorded. When the TCM receives a torque reduction failure message from the ECM, the code P2550 is stored.

What causes this problem with Torque Management Request Input Signal "B" Low?

• A damaged engine control module (ECM)
• Malfunctioning transmission control module (TCM)
• A software update in the engine control module (ECM)
• A software update in the transmission control module (TCM)
• Open or shorted harness in the engine control module (ECM)
• A poor electrical connection running in the engine control module (ECM)

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Next important thing you need to know about are the common symptoms for this OBD error code P2550 with your fuel volume control:

Common Symptoms

• Problems related to drivability
• Harsh shifting may be observed
• Fall in the fuel economy
• Engine stalling
• Rough at idle
• Bad acceleration

An illuminated service engine soon lamp (may not be illuminated immediately as it may show the code as pending)

Wish to correct this error code with your vehicle? Do you know what all you should do to make your car free from this code? Well, don’t worry! We are here to guide you:

• Repair or replace a faulty engine control module (ECM) or transmission control module (TCM) as per the requirements
• Mend or restore all the corroded or open harness in the engine control module (ECM)
• Make sure you update the software in the engine control module or transmission control module as required
• Fix a weak electrical connection running in the engine control module (ECM)

To do all this, you will need few high quality auto parts such as transmission, transmission control module, engine, PCM, wiring, connectors and so on. From where will you get them? From your local store? Well, why go there when you can order quality parts with us while sitting in the comfort of your home. So, just browse through our website and order your needed parts today.

It is essential to diagnose this fault code. Here are some steps which a mechanic should follow for diagnosing the problem that triggered a P2550 code to be stored:

• In order to enhance automatic transmission shift feel and boost component longevity, the transmission control module may request the PCM to decrease effective engine RPM and torque during specific shifting conditions.
• The PCM responds by retarding the ignition timing and inputting a signal to the transmission control module to indicate the task that has been completed successfully, when it receives such a request.
• A failure message is sent to the TCM, a code is stored followed by an illuminated MIL lamp when if the PCM fails to reduce the degree of torque produced by the engine. Consequently, these reduction requests and failure messages are sent between the controllers through the the controller area network (CAN).
• This controller area network (CAN) symbolizes a communication bus that enables multiple microcontrollers to communicate with one another without the requirement of a host computer. This is a message based protocol that is originally designed for automotive purposes.
• Utilized as a pipeline of information shared between two or more automotive control modules, the CAN bus network is actually a complex conglomeration of wiring harnesses and connectors.
• These controllers perform the task of virtually regulating every electrical function of the vehicle with the PCM being the chief controller.
• Various sensors transmit input data to control modules. Then these control modules emit output signals to the system parts and other control modules. For example: The PCM gets an input signal from the vehicle speed sensor.
• Then, this signal is systematically transferred to affected control modules that make use of the data to complete numerous other tasks.
• It should be noted that the cruise control module utilizes the data for speed control purposes, and the traction control system uses the data to monitor vehicle traction control strategy, and the anti-lock brake controller further compares the vehicle speed from the PCM with data inputs from individual wheel speed sensors in order to operate the anti-lock braking system. A large number of tools will be instrumental in attempting to successfully diagnose this code.
• To perform an accurate diagnosis, one might need a suitable OBD-II scanner (or code reader) and a digital volt/ohmmeter.
• A visual inspection of all wiring and connectors should be performed. Make sure you repair or replace all the loose, defective or corroded wiring and connectors as per the requirements.
• Then retest the system after repairs have been performed to ensure success. If all system wiring, connectors, and components (Including fuses) are functioning in order, the scanner (or code reader) should be connected to the diagnostic connector to record all stored codes and freeze frame data.
• Well, we advise you to register this information down as it can be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored.
• Then continue by clearing the codes again and operating the vehicle to see if it returns. This helps in determining whether or not the malfunction is intermittent.
• Perform a test drive, after the codes have been cleared to see if they return.
• You may have an intermittent condition, if the code fails to return back. These intermittent conditions can at times prove to be quite a task to diagnose and in extreme cases may have to be allowed to worsen before an accurate diagnosis can even be attempted.
• It is advised for you to take professional help if this type of a code is stored as it involves bulk of circuitry.
• With a specialized scanner (Autohex or Tech II) the trained mechanic may be able to determine the general area of the malfunction much more rapidly and easily than someone using a code reader and a digital volt ohmmeter.
• Test and disconnect every single pin of the CAN bus as it could prove to be time taking and cost prohibitive
• We also advise you to install some type of memory saving device, as the PCM and other controllers have chances of losing their memory and may require reprogramming
• Next, a specialized diagnostic CAN scanner will display pin values and control module operation without risking a meltdown. This helps in accurately diagnosing computer and circuitry problems by controlling vehicle operation while the vehicle is being operated
• Also, in order to diagnose this type of code employing a digital volt ohmmeter would entail testing thousands of circuits, independently
• One should be careful as even one misplaced probe could ruin expensive control modules which would require a complete programming of the vehicle. Then you should attempt to perform a continuity test after all control modules have been detached, and this could literally require 40-hours or more, depending upon the vehicle.
• If you choose to complete this monumental task, begin with a visual inspection of all the circuitry, connectors and fuses as some of the applications have 18 separate modules installed. The control modules should be probed for continuity with battery ground.
• Also, defective or disconnected system grounds often lead to the code being stored
• To diagnose the system ground discrepancies, an auxiliary ground cable can be used.
• Engine and transmission ground cables, straps, and wires are sometimes left hanging after all the repairs have been performed.
• Then locate any open or burnt electrical connectors as they may increase circuit resistance and lead to these types of codes to be stored. A CAN bus system wiring diagram and/or pin out value chart should be used. Then a digital volt ohmmeter should be used to probe continuity between individual controller connectors.
• Then compare the results with the manufacturer's referenced values and repair all the loose or corroded circuits as required.
• Well it is much more economical to restore or repair damaged wiring rather than attempting to remove it from the complicated web of wiring harnesses.

Common mistakes made when diagnosing the error code P2550

One of the most common mistakes made by the technician is failing to follow the specified diagnosis protocol. The protocol should be followed strictly and the components should be repaired or replaced in the right order to ensure a precise diagnosis. Failure in doing so results in a wrong replacement of the upstream oxygen sensor when the issue simply lies in electrical components.

P2551 - Torque Management Request Input Signal "B" High