What Does C1278 Mean?
Both steering wheel angle sensor signals (Signal 1 and Signal 2) are reporting faulted or conflicting data. The stability control system uses these redundant sensors to determine steering wheel position and rate of turn. With both signals faulted, the electronic stability control (ESC) system cannot determine driver intent and will be disabled. The ESC and possibly TCS warning lights will illuminate.
Common Causes
35%
Faulty steering wheel angle sensor (SAS) module with dual signal failure
25%
Steering column clockspring damage affecting sensor signal path
20%
Sensor not calibrated after alignment, suspension work, or steering component replacement
15%
Wiring harness fault in the steering column connector or under-dash area
5%
EBCM/stability control module unable to process sensor data
Diagnostic Steps
1
Monitor the steering wheel angle sensor PIDs in live data — observe both Signal 1 and Signal 2 values while slowly turning the steering wheel lock-to-lock. Both should show smooth, matching angle readings that correspond to wheel position.
2
Perform a steering angle sensor zero-point calibration using the scan tool — many vehicles require this after any alignment or steering component service. Follow OEM procedure (typically involves turning lock-to-lock and centering).
3
Inspect the steering column clockspring connector for damage, especially if the airbag light is also on or horn/cruise controls are intermittent — these share the clockspring path.
4
Disconnect and inspect the SAS connector at the steering column base for bent pins, corrosion, or contamination. Measure signal voltages — each signal typically outputs 0.5-4.5V analog or a digital CAN signal.
5
If calibration does not resolve the fault, replace the steering wheel angle sensor. On some vehicles this is integrated with the clockspring and both must be replaced as a unit.
Estimated Repair Cost
$150 - $900
Parts + labor, varies by vehicle and location
Both steering wheel angle sensor signals (Signal 1 and Signal 2) are reporting faulted or conflicting data. The stability control system uses these redundant sensors to determine steering wheel position and rate of turn. With both signals faulted, the electronic stability control (ESC) system cannot...
The most common cause of C1278 (STEERING Wheel Angle 1and 2 Signal Faulted) is: Faulty steering wheel angle sensor (SAS) module with dual signal failure
Typical repair costs for C1278 range from $150 to $900, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Electronic stability control (ESC) will be disabled, significantly reducing the vehicle's ability to correct oversteer or understeer conditions. ABS typically remains operational. Drive conservatively, especially in curves and on slippery surfaces. This repair should be prioritized as ESC is a critical safety system.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1278 to identify the root cause.
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Quick Info
Category
Chassis
System
Electronic Stability Control
Difficulty
Type
Manufacturer
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