The P068A error code indicates a problem with the power supply to your car’s Engine Control Module (ECM) or Powertrain Control Module (PCM). Specifically, it means the relay responsible for delivering voltage to the ECM/PCM has de-energized prematurely. This article delves into the intricacies of this error code, outlining its causes, symptoms, and diagnostic procedures.
A typical PCM (Powertrain Control Module)
What Does the P068A Code Mean?
The P068A diagnostic trouble code is a generic code applicable to most OBD-II compliant vehicles manufactured from 1996 onwards. This code signifies that the ECM/PCM has detected a fault in the de-energization process of its power relay. The relay, responsible for supplying voltage to the ECM/PCM, has switched off too early.
The PCM power relay is crucial for safely supplying battery voltage to the necessary PCM circuits. Activated by a signal from the ignition switch, this relay utilizes a controlled de-energization process to prevent voltage spikes that could damage the controller. A typical five-wire configuration includes wires for constant battery voltage, ground, ignition switch signal, PCM voltage supply, and a power relay sense circuit for PCM monitoring. When the PCM detects a fault in this de-energization sequence, the P068A code is stored, and the malfunction indicator lamp (MIL) might illuminate.
Severity and Symptoms of the P068A Code
The P068A code is considered severe and demands immediate attention. Ignoring this error could lead to a no-start condition or various drivability problems.
Symptoms associated with the P068A code can include:
- No-Start Condition: The engine may crank but fail to start.
- Delayed Start: The engine may take longer than usual to start.
- Drivability Issues: This can manifest as rough idling, misfires, stalling, or a lack of power.
Common Causes of the P068A Code
Several factors can contribute to the P068A error code:
- Faulty PCM Power Relay: The relay itself may be malfunctioning, causing premature de-energization.
- Blown Fuse or Fusible Link: A blown fuse or fusible link in the power supply circuit to the relay can interrupt the voltage supply.
- Open or Short Circuit: Damaged wiring or a short circuit between the power relay and the PCM can disrupt the signal or voltage flow.
Diagnosing the P068A Code
Diagnosing the P068A code requires a diagnostic scanner and a digital volt/ohmmeter (DVOM), along with a reliable source of vehicle-specific information like wiring diagrams, connector pinouts, and diagnostic flow charts.
- Scan for Codes: Connect the scanner to the vehicle’s diagnostic port, retrieve all stored codes and freeze frame data, and clear the codes.
- Test Drive: Test drive the vehicle to see if the code resets or the PCM enters readiness mode. If the code is intermittent, diagnosis becomes more challenging.
- Check for TSBs: Consult Technical Service Bulletins (TSBs) for known issues related to the P068A code and your specific vehicle.
- Visual Inspection: Inspect all related wiring, connectors, and harnesses for damage or disconnections.
- Test Fuses and Relays: Using the DVOM, test all system fuses and relays, particularly the PCM power relay’s supply voltage.
- Check Relay Output: Test the PCM power relay’s output voltage at the appropriate connector pins using the DVOM and compare it to specifications.
- Test PCM Input: If relay output is within specifications, test the corresponding circuits at the PCM connector for the relay’s signal.
If a signal is present at the PCM, suspect a faulty PCM or a programming error. If no signal is present, suspect an open or short circuit between the relay and the PCM. Remember to test fuses and fusible links under load to avoid misdiagnosis.
Conclusion
The P068A error code signifies a potentially serious issue with your vehicle’s ECM/PCM power supply. Addressing this issue promptly is crucial to prevent further damage and ensure safe and reliable vehicle operation. Utilizing the diagnostic steps outlined above can aid in identifying the root cause and implementing the necessary repairs. If you lack the necessary tools or expertise, consulting a qualified automotive technician is recommended.
