C1091

Code

Other C — Chassis

Speed Wheel Sensor All Coherency Failure

Brand: Other

Type: C — Chassis

Views: UK: 25 EN: 37 RU: 36

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Open, shorted, or intermittent wiring/connector between wheel sensor(s) and ABS module
Failed wheel speed sensor (magnetic/VR or Hall-effect)
Damaged or contaminated tone ring (reluctor) or sensor mounting
Poor ground or power supply to sensor circuits
ABS/traction control module fault or software/calibration issue
Electrical interference or improper replacement parts

Read all stored/active codes and freeze frame data with a capable scan tool
Compare live wheel speed data for all four wheels at low speed or on a lift
Visually inspect sensor, connector, wiring harness, and tone ring for damage or corrosion
Wiggle harness and connectors while monitoring live data for intermittent changes
Measure sensor supply voltage and ground at connector with ignition on
Measure sensor output with a digital oscilloscope or multimeter (AC for VR, DC/square wave for Hall)

VR (variable reluctance) sensor: AC waveform; low-speed amplitude typically small (tenths of a volt) rising with speed — should be a clean sinusoidal/AC pulse
Hall/active sensor: square wave 0–5 V (some systems 0–12 V) with frequency proportional to wheel speed and roughly 50% duty cycle
Frequency: increases linearly with wheel RPM (verify relative frequency among wheels)
Resistance: some passive sensors have a steady DC resistance (check OEM spec)
Connector supply: reference voltage for active sensors typically 5 V (check vehicle spec) and solid ground

Connect scan tool, record codes and live data for all wheel speed sensors. Note which wheel(s) show incoherent readings.
Visually inspect the suspect wheel sensor, tone ring, mount, and wiring for damage, contamination, or missing teeth.
With ignition ON (engine off), check sensor connector for correct reference voltage and good ground (active sensors).
Backprobe sensor signal and observe waveform while rotating the wheel (use oscilloscope if available). Compare waveform amplitude/frequency and shape to another known-good wheel.
Perform wiggle test on wiring and connectors while monitoring live data to find intermittent faults.
If waveform/output is absent or abnormal, measure sensor resistance (if passive) and compare to OEM spec; replace sensor if out of range.
Repair any damaged wiring, clean/replace corroded connectors, or service/replace a damaged tone ring or hub bearing.
After repairs, clear codes and perform road test or lift wheel rotation test to confirm coherent signals and that the code does not return.
If wiring and sensors are good but problem persists, consider ABS module diagnostics, software update, or module replacement per manufacturer procedures.

Corroded/wet connector at the affected wheel sensor
Frayed or chafed harness near suspension or wheel hub (intermittent contact when steering or moving)
Missing or broken teeth on the tone ring causing irregular pulses
Sensor gap out of specification or sensor misalignment
Short to battery or ground in sensor signal circuit
Failed sensor after recent brake/hub service or wheel bearing replacement