What does it mean?
U1051 is a Network (CAN bus, module communications) fault code. It indicates: Data Circuit Message .
Symptoms
- ABS, stability and brake warning lamps illuminated
- Brake lights not working, staying on, or working intermittently
- Cruise control refusing to engage because the system cannot confirm brake status
- Automatic transmission will not shift out of park without extra effort
- Engine idle or throttle response changing when the brake is applied
- Stop-start system disabled and hill hold unavailable
Likely causes
- Brake pedal position switch or sensor circuit fault, so no valid brake status can be transmitted
- Open circuit, high resistance or short on the data line between the brake module and the receiving modules
- Corroded or loose connector at the brake control module or at the pedal switch
- Transmitting module without proper power or ground because of a fuse, relay or corroded earth point
- Damaged bus wiring in the pedal box area, a common place for chafing and previous repairs
- Brake light circuit fault taking the pedal switch signal out of range
- Internal fault in the module that originates the brake message
How to fix it
- Have an assistant press the brake pedal while you watch the brake switch status in live data across several modules
- Inspect the brake pedal switch, its adjustment and its connector at the pedal box
- Check the brake light circuit and bulbs, since a shorted lamp circuit can corrupt the brake signal
- Test the serial data circuit between the sending and receiving modules for continuity, shorts to ground and to battery voltage
- Inspect the harness in the pedal box for chafing, crushed sections and poor previous repairs
- Do voltage drop tests on the transmitting module's power and ground circuits
- Clear the codes, then road test and recheck which modules still report the missing brake message
- Replace the pedal switch or the transmitting module as the tests indicate, then verify brake status is now seen by all modules