P0612 code meaning
Fuel Injector Control Module Relay Control
Powertrain system Generic code P06xx codes Check engine light
What P0612 means
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.
P0612 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P0612
- 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
Common causes of P0612
- Most likelyInjector module relay faulty (coil open, contacts welded)
- PossibleRelay control or feedback wire open or corroded, fuse
- PossibleLow battery voltage or ground problems
- Less likelyDriver in the engine module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injector control module relayRelay control circuitEngine control module
What each part of P0612 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. |
| 12 | The exact fault in that area. |
What to do next
- Note P0612 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 P0612
What does P0612 mean?
P0612 means "Fuel Injector Control Module Relay Control". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P0612?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0612 fail an emissions test?
Yes, it can. P0612 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0612 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0612 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.