Lost CAN Communication with Restraint Sensor M
Diagnostic trouble code U017C indicates that the airbag control module (also known as the SDM or SRS module) has lost Controller Area Network (CAN) communication with the restraint system sensor M. This sensor is part of the network of impact, acceleration, or occupant presence sensors that provide critical data to the SRS module for determining airbag deployment strategy in a collision. The loss of communication prevents the SRS module from receiving essential crash detection information, which can disable the airbag system.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Faulty restraint sensor M (internal damage or corrosion)
- Open or short circuit in the wiring between sensor M and the SRS module
- Damaged or corroded connector pins at sensor M
- CAN bus issues (CAN-H or CAN-L lines shorted or open)
- Faulty SRS module (SDM) preventing communication
- Poor ground or voltage reference to sensor M
3. Symptoms You Will Notice
- Airbag warning light illuminated on the dashboard
- Supplemental Restraint System (SRS) warning message displayed
- Airbags may be disabled or fail to deploy in a crash
4. Step-by-Step Diagnosis
Scan the vehicle for all stored codes and freeze frame data
Visually inspect the wiring and connectors for sensor M for damage, corrosion, or loose connections
Check CAN bus resistance and voltage at the sensor connector
Test sensor M per manufacturer specifications (resistance, voltage supply)
If wiring and sensor check out, suspect a faulty SRS module
5. Frequently Asked Questions
Is it safe to drive?▼
No, it is not safe to drive. The airbag system may be disabled, increasing the risk of injury in a collision. Have the vehicle diagnosed and repaired immediately.
How much does it cost to fix?▼
Repair costs typically range from $150 to $600, depending on whether the sensor, wiring, or SRS module needs replacement. Diagnostic fees are usually $100–$150.