Decoding OBD-II Code P068A: ECM/PCM Power Relay De-Energized Too Early

Understanding the P068A Trouble Code

The OBD-II trouble code P068A, a common diagnostic flag in modern vehicles (1996 onwards), signals an issue with the ECM/PCM (Engine Control Module/Powertrain Control Module) power relay. This code, applicable across various makes like Audi, Chrysler, Dodge, Jeep, Ram, and Volkswagen, indicates that the ECM/PCM has detected the power relay de-energizing prematurely. While considered a generic code, the precise diagnostic steps can vary depending on your vehicle’s specific year, make, model, and engine configuration.

In essence, the P068A code means the relay responsible for supplying battery voltage to your car’s computer (ECM/PCM) is shutting off sooner than expected. This relay is crucial as it safely delivers power to the sensitive electronic circuits of the PCM. Activated by the ignition switch, this relay is designed to de-energize in a controlled manner to prevent damaging voltage spikes. These relays typically feature a five-wire configuration: constant battery voltage, ground, an ignition switch signal, voltage supply to the PCM, and a power relay sense circuit for voltage monitoring by the PCM.

When the PCM detects an anomaly in this de-energizing process, specifically if it happens too early, the P068A code is triggered. This may also lead to the malfunction indicator lamp (MIL), or check engine light, illuminating on your dashboard.

A typical PCM powertrain control module, opened up:

Alt text: A detailed internal view of a vehicle’s Powertrain Control Module (PCM), highlighting its complex electronic components and circuitry, relevant for understanding engine management systems and diagnostics related to OBD-II code P068A.

Severity of DTC P068A

The P068A code is categorized as severe. It should not be ignored as it can lead to significant operational problems, ranging from a no-start condition to various engine drivability issues. Prompt diagnosis and repair are recommended to prevent further complications.

Common Symptoms of Code P068A

If your vehicle has stored a P068A code, you might experience several noticeable symptoms:

• Start-up Problems: This can manifest as a delayed engine start or a complete no-start condition, where the engine fails to crank or turn over.
• Engine Drivability Issues: Once started, the vehicle might exhibit various performance problems such as stalling, hesitation, rough idling, or reduced power. These symptoms occur because the premature de-energization of the power relay can disrupt the PCM’s ability to properly control engine functions.

Potential Causes of a P068A Code

Several factors can contribute to a P068A trouble code. Here are some of the common culprits:

• Faulty PCM Power Relay: The most likely cause is a defective power relay itself. The relay might be failing internally, causing it to de-energize prematurely or erratically.
• Blown Fuse or Fusible Link: A blown fuse or a damaged fusible link in the power supply circuit to the PCM power relay can interrupt the proper voltage supply, leading to the relay malfunctioning.
• Wiring Problems: An open or shorted circuit in the wiring between the power relay and the PCM can disrupt the signal and power flow, causing the relay to de-energize at the wrong time. This could be due to damaged wires, corroded connectors, or loose connections.

Diagnosing and Troubleshooting P068A

Diagnosing a P068A code requires a systematic approach using professional tools and reliable vehicle-specific information. Here’s a step-by-step troubleshooting guide:

Tools You’ll Need:

• OBD-II Diagnostic Scanner: To read and clear trouble codes, and access freeze frame data.
• Digital Volt/Ohmmeter (DVOM): For testing voltage, continuity, and resistance in circuits.
• Vehicle-Specific Service Information: Access to wiring diagrams, diagnostic flow charts, connector pinouts, component locations, and testing procedures for your specific vehicle model. This information is crucial for accurate diagnosis.

Diagnostic Steps:

1. Initial Scan and Data Collection:

   • Connect your diagnostic scanner to the OBD-II port.
   • Retrieve all stored trouble codes and freeze frame data. Freeze frame data captures the engine parameters at the moment the P068A code was set, which can provide valuable clues.
   • Record this information for future reference, especially if the code turns out to be intermittent.
   • Clear the codes and attempt to test drive the vehicle (if it’s drivable) to see if the code resets.

2. Verify Code Persistence:

   • If the PCM enters readiness mode after clearing the code and test driving, the issue might be intermittent. Intermittent faults are often harder to diagnose, as the problem may need to worsen to be consistently detectable.
   • If the code immediately resets or returns during the test drive, proceed with further diagnosis.

3. Check for Technical Service Bulletins (TSBs):

   • Consult your vehicle information source for Technical Service Bulletins (TSBs) related to the P068A code, your vehicle’s year, make, model, engine, and the symptoms you are experiencing. TSBs are manufacturer-issued guides that can offer known solutions for common problems.

4. Visual Inspection:

   • Perform a thorough visual inspection of all wiring and connectors related to the PCM power relay circuit.
   • Look for any obvious signs of damage, such as frayed or broken wires, corroded connectors, or loose connections. Repair or replace any damaged components as needed.

5. Circuit Testing:

   • Using your vehicle-specific wiring diagrams and connector pinout charts, identify the PCM power relay and its associated circuits.
   • Test Fuses and Fusible Links: Check all relevant fuses and fusible links in the PCM power relay circuit. Crucially, test fuses under load to ensure they are not falsely showing continuity when they are actually failing under current. Replace any blown fuses or fusible links with the correct amperage rating.
   • Verify Power Relay Input Voltage and Ground: Use your DVOM to confirm that the PCM power relay is receiving proper battery voltage and ground at the correct terminals. Refer to your wiring diagrams for pin locations.
   • Test Relay Output Performance: With power and ground confirmed at the relay input, use your DVOM to test the relay output voltage at the appropriate connector pins when the ignition is switched on. Compare your readings to the vehicle manufacturer’s specifications. If the output voltage is inadequate or missing, suspect a defective power relay and replace it.

6. PCM Circuit Testing:

   • If the power relay output is within specification, test the corresponding relay output circuits at the PCM connector. This will verify the integrity of the wiring between the relay and the PCM.
   • Check for Relay Output Signal at PCM: If you find the correct relay output voltage signal at the PCM connector, it suggests the wiring is intact up to the PCM. In this scenario, a defective PCM or a PCM programming error becomes a possibility, although less common.
   • No Relay Output Signal at PCM: If there’s no relay output voltage signal at the PCM connector, suspect an open or shorted circuit in the wiring between the PCM power relay and the PCM. Carefully trace the wiring and repair any faults.

Important Note: Always consult vehicle-specific repair information for accurate procedures and specifications. Improper diagnosis can lead to unnecessary component replacements and further complications.

Need Further Assistance with P068A?

If you’re still struggling to diagnose or resolve the P068A trouble code, consider seeking advice from experienced automotive technicians or utilizing online resources and forums dedicated to vehicle repair. Sharing your specific vehicle details and the steps you’ve already taken can help others provide more targeted and effective guidance.