U0403 code meaning
Invalid Data Received From Transfer Case Control Module
Network system Generic code U04xx codes Check engine light
What U0403 means
U0403 points to data from the transfer case control module, the unit that engages four-wheel drive and selects the range: its frames keep coming, yet the listener rejects what they carry. In GM's 2025 tables the ECM watches the secondary-axle signals from this module for faulty rolling counter, protection value or checksum, needs 8 bad results out of 18 to fail and assigns Type B (MIL on the second trip), whereas the lost-contact code U0102 there is Type C. On 2014-2016 Silverado, Sierra, Tahoe and Escalade GM saw U0403 with a Service 4WD message when ignition 1 voltage dropped out at fuse block terminals (PIT5391A). On 2019-2020 Ram 1500 with electronic transfer cases, U0403 and U1440 with traction lamp, driveline bumps and motor clicking were fixed by new drivetrain module software (08-083-20). U0303 is a software conflict.
U0403 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.3 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0403
- Service 4WD message
- Traction control or check engine light on
- Driveline bumps or clicking from the transfer case motor
Common causes of U0403
- Most likelySoftware of the transfer case or drivetrain control module (update available)
- PossibleIgnition voltage dropping out at fuse block terminals or relays
- PossibleFaulty range position sensor making the module send implausible values
- Less likelyTransfer case control module internally faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Transfer case control moduleCAN bus wiring
What each part of U0403 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 03 | The exact fault in that area. |
What to do next
- Note U0403 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 U0403
What does U0403 mean?
U0403 means "Invalid Data Received From Transfer Case Control Module". U0403 points to data from the transfer case control module, the unit that engages four-wheel drive and selects the range: its frames keep coming, yet the listener rejects what they carry. It is a generic code, so it means the same on every make.
Is it safe to drive with U0403?
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 U0403 fail an emissions test?
Yes, it can. U0403 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 U0403 to fix?
Difficulty: medium. A typical repair takes 0.3 to 3 hours of work. This is a job for a workshop.
Will U0403 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.