U0307 code meaning
Software Incompatibility With Glow Plug Control Module 1
Network system Generic code U03xx codes Check engine light
What U0307 means
Glow plug control module 1 switches the glow plugs of a diesel and exchanges data with the engine controller, usually over LIN. U0307 means that the controller does not accept the module's software. Volkswagen's 2014 Touareg TDI specification book sets it when the software check carried out over the LIN message fails. Ford's diesel OBD summaries of 2015 and 2023 list U0307 among the network faults and trip it when the glow module reports that it has fallen back to a safe glow mode; Ford's 2014 code interpretation marks it as a MIL code. GM tells technicians to check and update the module software on 2017 6.6 L L5P trucks after any glow plug replacement (PIP5524). CARB requires glow plug function to be monitored. Expect hard cold starts, white smoke and a lit MIL. U0106 means lost contact, U0407 invalid data.
U0307 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 U0307
- Long cranking or no start in cold weather
- White smoke and rough idle after a cold start
- MIL and glow plug warning lamp on
Common causes of U0307
- Most likelyGlow plug module software outdated or not matching the engine controller
- PossibleReplacement glow module of another part number or engine variant fitted
- PossibleEngine controller updated or replaced without updating the glow module
- Less likelyDisturbed LIN line corrupting the software check
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Glow plug moduleECMControl module software
What each part of U0307 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 07 | The exact fault in that area. |
What to do next
- Note U0307 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 U0307
What does U0307 mean?
U0307 means "Software Incompatibility With Glow Plug Control Module 1". Glow plug control module 1 switches the glow plugs of a diesel and exchanges data with the engine controller, usually over LIN. It is a generic code, so it means the same on every make.
Is it safe to drive with U0307?
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 U0307 fail an emissions test?
Yes, it can. U0307 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 U0307 to fix?
Difficulty: workshop only. A typical repair takes 0.4 to 2 hours of work. This is a job for a workshop.
Will U0307 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.