The Gear Shift Control Module is present on the data bus but the values it reports are implausible — out of range, frozen, or failing the checksum or rolling-count check. The receiving modules reject the data. Shift-by-wire gear selection may be wrong or blocked. Causes include a faulty sensor feeding the module, internal computation errors, a software or calibration mismatch after a repair, or bus interference corrupting the frames.
Medium severity. Can I keep driving?It depends on which control module has dropped out. If it affects the engine, brakes, or steering, do not continue your trip: call for roadside assistance.
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Most likely causes
- Shift module internal fault
- CAN corruption causing checksum errors
- Gateway module routing CAN messages incorrectly
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It can trigger limp mode.
What each character of U0404 means
- U: Communication network
- 0: Generic code: same on every make
- 4: Subsystem depends on the code range
- 04: Specific fault in that system
Frequently asked questions
Can I keep driving with code U0404?
It depends on which control module has dropped out. If it affects the engine, brakes, or steering, do not continue your trip: call for roadside assistance.
What causes code U0404?
The most common causes are: shift module internal fault; cAN corruption causing checksum errors; gateway module routing CAN messages incorrectly.
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.