P068B code meaning
ECM/PCM Power Relay De-Energized Performance Too Late
What P068B means
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.
P068B at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P068B
- Relay or module stays active after ignition off (fan or pump keeps running)
- Battery drains
- Possibly check engine light (depending on the maker)
Common causes of P068B
- Most likelyRelay contact sticking or welded
- PossibleRelay control wire shorted to ground (coil stays energised)
- PossibleRelay output or load line shorted to voltage
- Less likelyModule driver or software
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
ECM power relayRelay control circuitEngine control module
What each part of P068B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 6 | Area: computer (engine control module) and output circuits. |
| 8B | The exact fault in that area. |
What to do next
- Note P068B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P068B
What does P068B mean?
P068B means "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. It is a generic code, so it means the same on every make.
Is it safe to drive with P068B?
P068B does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P068B fail an emissions test?
P068B is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P068B to fix?
Difficulty: easy. A typical repair takes 0.3 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P068B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.