ECM/PCM Power Relay De-Energized Performance - Too Late
The P068B code indicates that the powertrain control module (PCM) detected the main power relay de-energized later than expected after the ignition was turned off. This relay supplies battery voltage to the PCM and other components. A delayed de-energization can cause battery drain, erratic system behavior, or failure to shut down properly. The issue often stems from a faulty relay, wiring problems, or a PCM internal fault.
1. Most Common Causes
- Faulty ECM/PCM power relay
- Corroded or loose relay socket terminals
- Short circuit or high resistance in relay control circuit
- Internal PCM failure
2. Symptoms You Will Notice
- Battery drains overnight or after short trips
- Engine may not start or cranks slowly
- Check Engine Light illuminated
- Electrical accessories behave erratically after key off
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Inspect the ECM/PCM power relay and its socket for corrosion, damage, or loose pins.
Step 3: Test relay coil resistance and switching operation with a multimeter.
Step 4: Check for battery voltage at relay terminals with key on and off.
Step 5: If relay and wiring are okay, test PCM ground and power inputs; consider PCM replacement if all else fails.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended because the relay may fail to de-energize, causing battery drain and potential no-start conditions. Have it diagnosed promptly.
How much does it cost to fix?▼
Typically $50-$150 for relay replacement and basic diagnostics. PCM replacement can cost $500-$1000+.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.