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

The engine module switches its main relay coil to ground (control circuit), reads the switched voltage back on a sense line and keeps the relay on briefly after ignition off to save learned values. P068B is the counterpart of P068A: after ignition off and the module's switch-off command the relay voltage remains – the relay drops out late or not at all. GM Europe's 2.0 diesel runs this check from ignition off until the module shuts down and names a control line shorted to ground (coil stays energised), an output line shorted to voltage or a sticking contact as causes, without lighting the MIL. Modules and loads then stay powered and the battery drains. GM reports the same electrical faults as P0686/P0690 instead. A Ford diesel table lists 'P068B' for a memory error, which is evidently a typo for P06B8.

Medium severity. Can I keep driving?It depends on the symptoms. If the car is running normally you can go to a repair shop; if it goes into limp mode, drive as little as possible.

Symptoms

Relay or module stays active after ignition off (fan or pump keeps running)
Battery drains
Possibly check engine light (depending on the maker)

Most likely causes

Relay contact sticking or welded
Relay control wire shorted to ground (coil stays energised)
Relay output or load line shorted to voltage
Module driver or software

What to check, in order

Start with the simplest. You can tick off each step.

Check the battery and grounds
Compare the reading with other engine data while varying the engine speed.
Clear the code and see if it returns
If it is a reference voltage code, disconnect sensors one at a time and see if the voltage recovers
Check whether a software update is available
Do not replace the control module without a full diagnosis

Good to know

Repair difficulty: easy

What each character of P068B means

P: Powertrain: engine and transmission
0: Generic code: same on every make
6: Control modules and outputs
8B: Specific fault in that system

Frequently asked questions

Can I keep driving with code P068B?

It depends on the symptoms. If the car is running normally you can go to a repair shop; if it goes into limp mode, drive as little as possible.

What causes code P068B?

The most common causes are: relay contact sticking or welded; relay control wire shorted to ground (coil stays energised); relay output or load line shorted to voltage.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.