U030B code meaning
Software Incompatibility With Glow Plug Control Module 2
Network system Generic code U03xx codes Check engine light
What U030B means
U030B is the counterpart of U0307 for a second glow plug control module, used where an engine splits its glow plugs between two drivers, say one per bank. It is stored when the engine controller rejects the software or calibration identity of module 2, typically after only one of the two units was replaced or flashed. No manufacturer documents U030B publicly. A GM patent explains the dialogue behind it: glow plug faults are judged from several messages passed between engine and glow controller, with a strategy that changes with how long the plugs have been on in a drive cycle. GM also asks for the glow module software to be brought up to date after glow plug work (PIP5524). CARB requires glow plugs to be checked for proper response. U019C stands for lost contact, U049D for invalid data. Cold starts suffer; a MIL is likely.
U030B at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyWorkshop only
- Typical labor0.4 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U030B
- Hard cold start, uneven running until warm
- White smoke after starting in the cold
- MIL and glow plug warning on
Common causes of U030B
- Most likelyOnly glow module 2 (or only module 1) replaced, software levels now differ
- PossibleModule of another part number or engine variant installed in position 2
- PossibleEngine controller updated without the second glow module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Glow plug module 2ECMControl module software
What each part of U030B means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 0B | The exact fault in that area. |
What to do next
- Note U030B 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 U030B
What does U030B mean?
U030B means "Software Incompatibility With Glow Plug Control Module 2". U030B is the counterpart of U0307 for a second glow plug control module, used where an engine splits its glow plugs between two drivers, say one per bank. It is a generic code, so it means the same on every make.
Is it safe to drive with U030B?
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 U030B fail an emissions test?
Yes, it can. U030B 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 U030B to fix?
Difficulty: workshop only. A typical repair takes 0.4 to 2 hours of work. This is a job for a workshop.
Will U030B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.