U0306 code meaning
Software Incompatibility With Fuel Injector Control Module
What U0306 means
Some diesels fire their injectors through a separate fuel injector control module that raises the voltage and opens each injector when the engine controller commands it; Ford's 6.0 L Power Stroke used such a FICM at about 48 V, and GM's 2005 Duramax table watches its injector driver by a CAN status bit that must toggle every 20 ms. U0306 means the controllers judge the module's software or calibration as not matching, for example after a used or remanufactured FICM was fitted. Ford's 2014 OBD-II code interpretation carries U0306 without its MIL marker; other makers may rate it differently, because injection timing and quantity decide emissions. U0105 stands for lost contact, U0406 for invalid data. Depending on the strategy the engine runs roughly, drops into reduced power or will not start.
U0306 at a glance
- Check engine lightUsually not
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0306
- Hard start or no start, engine may crank without firing
- Rough running, misfire or reduced power
- Further injector or injector module codes stored
Common causes of U0306
- Most likelyUsed, remanufactured or wrong-variant injector module fitted without programming
- PossibleEngine controller reflashed or replaced while the injector module kept old software
- Less likelyProgramming of the injector module interrupted, e.g. by low battery voltage
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Injector driver moduleECMControl module software
What each part of U0306 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 06 | The exact fault in that area. |
What to do next
- Note U0306 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 U0306
What does U0306 mean?
U0306 means "Software Incompatibility With Fuel Injector Control Module". Some diesels fire their injectors through a separate fuel injector control module that raises the voltage and opens each injector when the engine controller commands it; Ford's 6.0 L Power Stroke used such a FICM at about 48 V, and GM's 2005 Duramax table watches its injector driver by a CAN status bit that must toggle every 20 ms. It is a generic code, so it means the same on every make.
Is it safe to drive with U0306?
Drive gently and only to a workshop. With U0306 the car can go into limp mode (reduced power) to protect itself.
Will U0306 fail an emissions test?
Yes, it can. U0306 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 U0306 to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will U0306 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.