U049D code meaning
Invalid Data Received From Glow Plug Control Module 2
Network system Generic code U04xx codes Check engine light
What U049D means
U049D is logged when a controller, normally the engine control module, still hears from the second glow plug control module but cannot trust what it reports, for instance because a counter, checksum or plug status value is out of line. A second unit is found on diesels that split their glow plugs between two drivers. No manufacturer documents this code publicly; it mirrors U0407, which covers module 1. CARB 1968.2 obliges diesel OBD to verify that glow plugs respond to commands and draw proper current, a check the engine controller can only make with valid module data. A GM patent shows both controllers exchanging timed messages and flagging late ones as faults. U019C means the module is silent, U030B a software mismatch. Hard cold starts and a lit MIL are likely.
U049D at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U049D
- Check engine or glow plug warning light on
- Long cranking or misfire on cold starts
- White smoke until the engine warms up
Common causes of U049D
- Most likelyCorroded or loose connector or data wire at glow plug module 2
- PossibleSupply voltage sagging while the glow plugs draw high current
- PossibleGlow plug control module 2 internally faulty
- Less likelyModule or engine controller software not matched after replacement
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Glow plug module 2
What each part of U049D means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 9D | The exact fault in that area. |
What to do next
- Note U049D 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 U049D
What does U049D mean?
U049D means "Invalid Data Received From Glow Plug Control Module 2". U049D is logged when a controller, normally the engine control module, still hears from the second glow plug control module but cannot trust what it reports, for instance because a counter, checksum or plug status value is out of line. It is a generic code, so it means the same on every make.
Is it safe to drive with U049D?
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 U049D fail an emissions test?
Yes, it can. U049D 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 U049D to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will U049D clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.