Technical Description of OBD-II Trouble Code
Performance of ECM/PCM Power Relay De-Energized – Occurring Too Early
What does that signify?
This is a generic diagnostic trouble code (DTC) that is applicable to numerous OBD-II vehicles (1996-newer). This includes vehicles from Audi, Chrysler, Dodge, Jeep, Ram, Volkswagen, and others. While it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration.
When code P068A is stored, it indicates that the engine/powertrain control module (ECM/PCM) has detected a flaw in the de-energizing procedure for the relay that supplies it with voltage. In this case, the relay has de-energized prematurely.
The PCM power relay is utilized to safely apply battery voltage to the appropriate PCM circuits. It is a contact type relay that is activated by a signal wire from the ignition switch. This relay must be gradually de-energized in a controlled manner to prevent voltage spikes and potential damage to the controller. This type of relay typically employs a five-wire design. One wire carries constant battery voltage, another wire is for ground, a third wire carries a signal from the ignition switch, a fourth wire supplies voltage to the PCM, and the fifth wire is the power relay sense circuit used by the PCM to monitor power relay voltage.
If the PCM detects a malfunction in de-energizing the ECM/PCM power relay, it will store a code P068A and may illuminate a malfunction indicator lamp (MIL).
A typical opened up PCM powertrain control module:
What is the severity of this DTC?
A P068A should be considered severe and addressed accordingly. It may result in a no start condition and/or various drivability issues.
What are some of the symptoms of the code?
Symptoms of a P068A trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P068A troubleshooting steps?
To diagnose a code P068A, you will need a diagnostic scanner and a digital volt/ohmmeter (DVOM).
You will also require a reliable source of vehicle information that provides diagnostic flow charts, wiring diagrams, connector face views, connector pin-out charts, component locators, component and circuit testing procedures, and specifications. All of this information is necessary for a successful diagnosis of a code P068A.
Connect the scanner to the vehicle diagnostic port and retrieve all stored codes and freeze frame data. Take note of this information as it may be useful if the code is intermittent.
After recording all relevant information, clear the codes and, if possible, test drive the vehicle until the code is reset or the PCM enters readiness mode.
If the PCM enters readiness mode, the code is intermittent and will be even more challenging to diagnose. The condition that caused the P068A to be stored may need to worsen before an accurate diagnosis can be made. However, if the code fails to reset and there are no drivability symptoms, the vehicle can be operated normally.
Refer to your vehicle information source for any technical service bulletins (TSB) that match the stored code, vehicle (year, make, model, and engine), and exhibited symptoms. If you find the appropriate TSB, it may provide helpful diagnostic information.
If the P068A code is immediately reset, visually inspect the system-related wiring and connectors. Repair or replace any broken or unplugged harnesses as necessary.
If the wiring and connectors appear to be functional, use your vehicle information source to obtain the necessary wiring diagrams, connector face views, connector pin-out charts, and diagnostic flow charts.
Once you have the relevant information, test all system fuses and relays to ensure that the PCM power supply relay is receiving battery voltage.
Obtain the PCM power relay de-energizing parameters and apply them to the following diagnostic steps.
If constant (or switched) voltage is not present at the power relay connector, trace the appropriate circuit back to the fuse or relay from which it originates. Repair or replace any defective fuses or fusible links as necessary.
If power relay supply input voltage and ground are present on all appropriate terminals, use your DVOM to test the relay output performance at the appropriate connector pins. If the power supply relay output circuit voltage is inadequate, suspect that the relay is defective.
If the PCM power supply relay output voltage is within specifications on all terminals, test the corresponding relay output circuits at the PCM.
If a relay output voltage signal is discovered at the PCM connector, suspect a defective PCM or a PCM programming error.
If there is no appropriate PCM power relay output voltage signal discovered at the PCM connector, suspect an open or shorted circuit between the PCM power relay and the PCM.
