How are Powertrain Control Module issues diagnosed?
When the PCM is suspected of failure, the particular specifications of that unit must be referenced so the technician knows what the correct readings should be. The PCM will be tested by comparing actual readings to specified readings, following any specific diagnostic steps for that PCM, and confirming diagnosis after each pin has been tested for all necessary parameters. Since there are so many possible failure symptoms, it is not possible to speculate which pin to check, but reference materials will guide the technician through the process of locating the pins/wires that correspond to the issue they are chasing.
How are Powertrain Control Modules replaced?
Replacing the PCM is normally easy since diagnostics will require the PCM be accessed for diagnostic testing prior to replacement. The technician may need component location reference material to find where the manufacturer installed the PCM. In most vehicles, the PCM is in the engine bay, but a few manufacturers place the PCM inside the vehicle. In some vehicles, the PCM is even located in the trunk. Once the PCM has been located, any obstructions to testing and replacement must be removed, and testing begins. If the PCM fails diagnostic testing, the PCM will be unplugged, replaced, and reconnected to the vehicle prior to final assembly and testing.
RepairPal Recommendations for Powertrain Control Module issues
Electrical diagnostics in general can be problematic, and there are many variables to account for. When electrical problems arise, diagnostics may take several hours to complete, or just a few minutes. This will significantly impact the cost of repairs. Choosing a facility with proper equipment and training for their staff may significantly reduce diagnostic time needed.
What to look out for when dealing with Powertrain Control Module issues
The battery connects directly to the engine, meaning it is grounded to the same point as many engine sensors. If the battery is incorrectly installed in a vehicle, such as installing or jump-starting the battery backwards, the PCM can be destroyed, along with some sensors and wiring. In many occasions, the PCM connector, harness, or pins inside the connector socket fail, and cannot make a proper connection to the PCM. Except for a broken or missing pin, these items can be replaced, and the vehicle retested.
Can I replace the Powertrain Control Module myself?
Replacing the PCM on most vehicles is fairly easy, but accessing the control module usually requires searching behind panels if the component cannot be identified through a vehicle repair database. In many cases, the PCM looks much like a few other computers that are mounted in the vehicle, and removing a few panels to find the wrong module will quickly become frustrating. If proper experience, and reference materials are available, the PCM can be replaced, but many will need to be calibrated by the manufacturer. If this process is understood, and the PCM is adapted to the vehicle, this is a money saver, however, if diagnostic procedures are not fully understood, this should be trusted to a professional.
