What it means
A control module is not receiving expected messages from Restraints System Sensor M. The code indicates a communication fault; the sensor's specific role depends on the vehicle.
At a glance
- Usually lights the warning light of the system that lost communication
How it works
Restraints System Sensor M supplies vehicle-specific data to the restraint system through the vehicle network. U017C is set when a control module does not receive Sensor M messages for the required time, with possible causes including loss of sensor power, damaged wiring, gateway routing trouble, or a CAN termination fault.
Common causes
Most likely first.
- Sensor unpowered or wiring broken
- Gateway module routing CAN messages incorrectly
- CAN terminating resistor (120 Ω) drifted out of spec
Symptoms
- Airbag or restraint-system warning
- Restraint functions associated with the sensor may be impaired
- Other communication codes
How to diagnose it
- Scan all modules and inspect freeze-frame data to see whether U017C coincided with low voltage or other network codes.
- Use vehicle service information to find Sensor M, then inspect its connector and harness for corrosion, damage, loose pins, or water entry.
- Measure Sensor M power and ground and compare them with the manufacturer's specification.
- Check gateway communication codes and determine whether other modules on the same network are also missing.
- Test CAN wiring and termination with the manufacturer's specified procedure.
- If power, wiring, gateway routing, and network termination check out, test Sensor M using the manufacturer's restraint-system diagnostic steps.
Common fixes
- Restore Sensor M power or ground by repairing the failed connection or circuit.
- Repair damaged wiring or clean and secure the sensor connector.
- Repair a confirmed CAN bus or gateway routing fault.
- Replace Sensor M if testing confirms an internal failure.
Can I keep driving?
The restraint function linked to Sensor M may be impaired in a crash, so arrange prompt diagnosis and drive cautiously. Do not handle the sensor or its wiring without following the vehicle’s restraint-system safety procedure.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.