P068B: ECM or PCM Power Relay De-Energized Performance Too Late

What it means

Same as P068A with the relay dropping out later than the calibrated window allows - keeps the ECU powered too long after key-off, drains the battery.

At a glance

• Usually lights the check-engine light

How it works

After key-off, the ECM or PCM power relay should disconnect controller power within a calibrated window. P068B sets when the relay stays energized too long, potentially keeping the controller awake and drawing down the battery.

Common causes

Most likely first.

1. Power relay contacts sticking or welded
2. Faulty relay
3. Damaged relay-control wiring
4. Powertrain control module fault

Symptoms

• Check engine light on
• Possible limp mode or no-start
• Multiple follow-up faults across modules
• Reset/relearn may be needed after repair

How to diagnose it

1. Record freeze-frame data and scan for related relay, voltage, and controller-awake codes.
2. Check whether the battery goes flat after the vehicle is parked and whether the controller or related systems remain awake after key-off.
3. Inspect the relay, socket, and control wiring for sticking contacts, heat damage, corrosion, or shorts.
4. Monitor relay output and control after key-off using the manufacturer’s diagnostic procedure to confirm that power persists too long.
5. Test for a sticking or welded relay and check whether the control circuit or controller is keeping it energized.

Common fixes

• Replace a relay with sticking or welded contacts.
• Repair damaged or shorted relay-control wiring.
• Clean or repair corroded relay and socket connections.
• Repair or replace the controller only after confirming the relay and control circuit are not the cause.

Can I keep driving?

The vehicle may be drivable, but a relay that stays energized can drain the battery and leave you unable to start. Avoid leaving it parked for long periods until the fault is repaired.