Powertrain, generic · Computer and auxiliary outputs

P0612 Fuel Injector Control Module Relay Control

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

Some diesels have a separate injector driver module that is powered through a relay switched by the engine module – GM's 6.6 L Duramax LB7/LLY with its injector driver unit, Ford's 6.0 L Power Stroke with its injector control module. P0612 means the commanded relay state and the voltage measured back at the output do not match. GM checks this with ignition on and the CAN link initialised, outside the shutdown phase, and sets the code after 30 of 50 checks at 125 ms; the lamp follows after two trips. If the relay fails, the injector module gets no power – the engine does not start or stalls; if it does not drop out, the module stays powered and drains the battery. Newer diesels have the injector drivers inside the engine module and use P062D/P062E instead. A fault reported by the injector module itself is P0611.

Likely causes

Injector module relay faulty (coil open, contacts welded)
Relay control or feedback wire open or corroded, fuse
Low battery voltage or ground problems
Driver in the engine module faulty

Symptoms

  • Engine does not start or stalls while driving
  • Check engine light (GM after two trips)
  • Battery drain if the relay does not drop out
  • Often together with P0611 or injector codes

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–900
Time0.5–3 h

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

Parts involved

fuel injector control module relayrelay control circuitengine control module

Related codes

P0611P06ECP0201P2146P062D

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com.