Invalid Steering Wheel Angle Sensor ID
The steering wheel angle sensor is sending an unrecognized identification signal to the vehicle's computer, like a keycard reader rejecting a valid card due to a communication error. The ECU cannot verify the sensor's legitimacy and won't trust its steering angle data.
The ECU communicates with the steering wheel angle sensor via CAN bus or dedicated circuit to verify its identity code. The sensor broadcasts an ID string that the ECU cross-references against a valid list. If the ID doesn't match expected values or is corrupted, the fault triggers.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Sensor ID Code | Matches programmed sensor identification string | ID mismatch, invalid format, or communication timeout |
| Signal Integrity | Clear CAN message with valid checksum | Corrupted data frame or failed handshake protocol |
Code C1938 is classified as a serious fault. If your check engine light is flashing — not just steady — pull over safely and do not continue driving. A flashing CEL indicates an active misfire or critical failure that can cause catalytic converter damage within minutes or permanent engine harm within miles. Contact a certified mechanic immediately. Do not attempt roadside repairs on high-severity codes unless you are trained to do so.
Once the fault is repaired, C1938 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.