Powertrain, generic · Computer and auxiliary outputs

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

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

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.

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

Symptoms

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

Repair estimate

DifficultyEasyDIY possible
Parts and labour€10–250
Time0.3–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

ecm power relayrelay control circuitengine control module

Related codes

P068AP0686P0690P0685P2610

References: law.cornell.edu, saabwisonline.com.