C1278
STEERING Wheel Angle 1and 2 Signal Faulted
Chassis Chassis/Safety Steering Angle Sensor 🔴 Serious — Stop or limit driving
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What This Actually Means
In plain language — no jargon

Your car's steering wheel angle sensors aren't communicating properly with the stability control system, like a compass giving conflicting readings. The vehicle can't accurately track how much you're turning the wheel, which affects safety features.

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Symptoms You May Notice
3 known symptoms for this code
Stability control or traction control warning light illuminated
Steering wheel angle display shows erratic or frozen values
Loss of electronic stability control or lane-keeping assist function
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors two redundant steering angle sensor signals to ensure accurate wheel position for stability and safety systems. It compares both signals for consistency and checks that values fall within expected physical limits based on steering input rate and vehicle dynamics.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Steering Angle Signal Voltage 0.5–4.5V with smooth variation Voltage out of range, signal dropout, or mismatch >10° between sensors
Signal Rate of Change <100°/second >100°/second or abrupt jumps indicating electrical noise
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Steering wheel angle sensor connectors
Inspect and clean the two sensor connectors at the base of the steering column for corrosion or loose pins.
2
Steering wheel angle sensor wiring harness
Check the wiring harness for cuts, pinches, or damage along the steering column and beneath the dash.
3
Steering wheel angle sensor (redundant unit)
Replace the faulty sensor unit if voltage readings are unstable; typically requires steering wheel removal and recalibration.