Code
C0309
HUMMER
C — Chassis
Right Rear Wheel Speed Sensor Circuit Intermittent
AI status
Completed
Completed
100%
Causes
- Damaged or chafed wiring harness to right rear wheel sensor
- Corroded/loose connector or poor terminal contact at sensor
- Faulty right rear wheel speed sensor (passive VR or active Hall/IC)
- Damaged or missing tone ring / reluctor teeth or heavy debris
- Intermittent short to chassis ground or battery voltage
- Poor sensor air gap or incorrect sensor mounting
Symptoms
- ABS warning light illuminated
- Traction control / stability control (TC/ESC) warning lights
- Intermittent ABS operation or unexpected ABS activation
- ABS or traction control disabled until code cleared and fault resolved
- Possible uneven braking or diagnostic trouble during low-speed maneuvers
What to check
- Read and record codes and freeze frame with a scan tool; note any related codes
- Check live wheel speed data while rotating each wheel (drive or lift and spin) and compare sensors
- Visually inspect sensor, connector and wiring for damage, corrosion, broken pins or loose clips
- Backprobe connector while spinning wheel to observe signal behavior (use proper safety and wheel support)
- Measure sensor resistance (passive) or supply/reference/ground and signal (active) per manufacturer spec
- Wiggle wiring harness and connectors while monitoring live data to reproduce intermittent behavior
Signal parameters
- Passive (variable reluctance) sensor: DC resistance typically from several hundred to a few thousand ohms; generates AC sine-wave whose amplitude increases with wheel speed.
- Active (Hall/IC) sensor: requires reference voltage (commonly 5 V) and ground; signal typically a square/pulse wave from ~0–5 V with frequency proportional to wheel speed.
- Normal behavior: stable, continuous pulse stream proportional to wheel speed. Intermittent faults: dropouts, noise, or irregular amplitude/frequency.
Diagnostic algorithm
- Use a scan tool to record C0309 and any other ABS/traction codes. Note when the fault occurs (vehicle speed, turns, bumps).
- Visually inspect right rear hub area: sensor, bracket, tone ring, wheel bearing seal, and wiring routing for chafing or damage.
- With vehicle safely supported, spin the right rear wheel and observe wheel speed values on scan tool. Compare to other wheels for dropouts or noise.
- Backprobe the sensor connector while spinning wheel. For passive sensors check AC output; for active sensors check reference voltage, ground, and signal waveform with an oscilloscope or DSO.
- Perform a wiggle test on the harness and connector while monitoring live data to reproduce intermittent behavior. Repair any damaged wiring or connectors found.
- Measure sensor resistance (disconnect sensor) and compare to specification. If signal absent or out of range, replace sensor.
- Inspect and, if necessary, clean or replace the tone ring/reluctor; correct excessive air gap or damaged mounting.
- Repair or replace wiring/connector as required (solder and heat-shrink or replace pigtail/connector). Avoid using temporary splices in ABS circuits.
- After repairs, clear codes and test drive under the same conditions to confirm fault does not return. Re-scan to ensure no additional faults.
Likely causes
- Broken/chafed wiring or pinched harness at suspension pivot/wheel
- Corroded or water-intruded sensor connector
- Failed wheel speed sensor at the right rear wheel
- Contaminated/damaged tone ring causing sporadic pulses
Fault status
Status
Intermittent signal detected from the right rear wheel speed sensor circuit. The ABS/ESC module observed irregular or missing wheel speed pulses from the right rear sensor. This may trigger ABS and traction/stability warnings and may disable related functions until repaired.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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