Code
C0290
HUMMER
C — Chassis
ABS Wheel Speed Sensor Circuit Fault
AI status
Completed
Completed
100%
Causes
- Damaged or failed wheel speed (ABS) sensor
- Open or shorted wiring harness to the sensor
- Corroded/loose sensor connector or poor pin contact
- Damaged or missing reluctor/tone ring (broken teeth, heavy rust, debris)
- Excessive air gap between sensor and reluctor
- Faulty ABS module or internal connector problem
Symptoms
- ABS warning lamp ON
- Traction control/ESC warning or disabled
- ABS not engaging on hard braking / altered brake pedal feel during ABS events
- Driveability usually unaffected except loss of ABS/traction control functions
- Possible intermittent ABS activation or erroneous ABS events
What to check
- Scan ABS module for active and stored codes and freeze-frame data
- Use a scan tool to monitor raw wheel speed sensor data for all four wheels while spinning each wheel (on lift) or during road test
- Visually inspect sensor, connector, and wiring for damage, corrosion, bent pins, or water intrusion
- Inspect reluctor/tone ring on hub/axle for missing/broken teeth, heavy rust, or debris
- Check sensor mounting and air gap; verify correct orientation and torque of mounting fastener
- Backprobe connector and check for proper reference voltage and ground (if Hall-type sensor)
Signal parameters
- Hall-effect sensor: reference/pull-up typically 5 V; digital square-wave output 0–5 V (low/high switching) with frequency proportional to wheel speed
- Inductive (VR) sensor: AC waveform; amplitude increases with speed — typically tens to hundreds of millivolts up to ~1 V AC or higher depending on speed and sensor design
- Resistance (VR sensor): typically several hundred to a few thousand ohms — consult vehicle service spec for exact value
- Expected continuity: low ohms from sensor signal to module pin; open/infinite indicates broken circuit; short to ground or battery indicates wiring short
- Frequency: proportional to wheel RPM (Hz increases with wheel speed); compare frequency and waveform symmetry to other wheels
Diagnostic algorithm
- Retrieve freeze frame and all stored ABS codes; note which wheel/circuit is indicated and any related codes.
- Visually inspect the suspect wheel sensor, connector, wiring loom, and reluctor/tone ring for damage, corrosion, missing teeth, or debris. Repair obvious damage.
- With ignition ON (engine off) backprobe the sensor connector: for Hall sensors verify reference voltage (≈5 V) and signal toggling while spinning the hub; for VR sensors measure AC voltage while spinning the wheel. Compare to opposite wheel.
- Measure sensor resistance and continuity to the ABS module connector. Replace sensor if open or out of specification. Repair wiring if open/short detected.
- Perform a wiggle test on harness and connector while watching live data for intermittent faults; repair chafing or replace harness as required.
- Inspect and/or measure air gap between sensor tip and tone ring; correct gap and re-secure sensor if out of spec.
- If tone ring is damaged, cleaned, or misaligned, repair or replace it (or hub/axle assembly as required).
- After repairs, clear codes and perform road test or lift-spin test while monitoring wheel speed outputs to confirm proper operation.
- If wiring and sensor check good but fault persists on module input, consider ABS control module connector issues or module failure and follow manufacturer module diagnostics (isolate module inputs before replacement).
Likely causes
- Corroded connector or damaged wiring at wheel (most common)
- Contaminated or cracked sensor (road debris, corrosion)
- Reluctor/tone ring damage or buildup changing tooth signal
- Sensor air gap too large after recent service (wheel bearing/axle work)
- Intermittent open/short in harness due to chafing
Fault status
Status
ABS control module detected abnormal/no signal from wheel speed sensor circuit. Possible open, short, intermittent, or out-of-range sensor signal. Inspection of sensor, tone ring, and wiring is required.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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