Code
C05F1
Generic
C — Chassis
Rear Drive Shaft Speed Sensor Circuit High
AI status
Completed
Completed
100%
Causes
- Open or shorted sensor wiring (short to battery voltage)
- Corroded or loose connector at sensor or module
- Failed rear drive shaft speed sensor (Hall or VR type)
- Faulty ABS/TC/transfer case control module or poor ground
- Incorrect sensor air gap or damaged tone ring/reluctor
- Aftermarket or incorrect replacement sensor
Symptoms
- ABS/traction/stability warning lamp illuminated
- Cruise control or speedometer errors or inconsistent readout
- Reduced traction control or limp-in modes engaged
- Erratic or delayed shifting (automatic transmissions that use shaft speed)
- Possible driveline vibration or unusual noises if tone ring damaged
What to check
- Visual inspection of sensor, connector, wiring harness and tone ring for damage or contamination
- Check connector pins for corrosion, bent pins and secure fit
- Measure sensor supply voltage and ground at the connector with ignition on
- Measure sensor output with a multimeter (DC for Hall, AC for VR) and compare to known good values
- Use an oscilloscope to inspect waveform shape, amplitude and frequency while rotating the shaft
- Check continuity and resistance between sensor and module, and for shorts to battery and ground
Signal parameters
- Hall-effect sensor: typical idle resting voltage ~0.4–4.6 V; switching square-wave between ~0.5–4.5 V
- VR (variable reluctance) sensor: open-circuit resistance typically 200–2000 Ω (manufacturer-specific)
- VR AC output: ~0.1–1.5 Vrms at low shaft speed, increasing with rpm
- Pulse frequency: proportional to shaft RPM (example 20–200+ Hz depending on vehicle and speed)
- Expected signal change: clean, regular pulses with amplitude and frequency proportional to rotation; a constant high DC indicates failure or short to battery
Diagnostic algorithm
- Read and record freeze-frame and any other stored codes. Note conditions when C05F1 set (speed, temperature, ignition state).
- Visually inspect sensor, tone ring, and wiring for damage, contamination, missing teeth, or loose connectors. Repair or replace damaged parts as needed.
- With ignition ON, backprobe sensor connector: verify reference voltage/pull-up (for Hall) or continuity to ground (for VR) per vehicle specs. If reference voltage present, proceed; if not, check upstream fuses/relays and module.
- Measure sensor output while slowly rotating the drive shaft/wheel. For Hall sensor expect a switching DC waveform; for VR expect AC voltage that increases with speed. Use an oscilloscope for best view.
- If output is stuck high (constant battery voltage) or excessively high, disconnect sensor and measure voltage at harness. If high voltage remains at harness, suspect short or module fault. If voltage disappears with sensor disconnected, suspect sensor internal failure.
- Check resistance/continuity of sensor wiring between sensor connector and control module. Repair any short to battery or open circuits found.
Likely causes
- Connector pushed off pin or water ingress causing high/erratic voltage
- Damaged insulation allowing wire to short to battery feed
- Sensor internal electronics failed (Hall sensor output stuck high)
- Wiring routed near high-current harness causing induced voltage
- Broken or missing reluctor teeth causing intermittent high amplitude pulses
Fault status
Status
Rear drive shaft speed sensor circuit reports high signal/voltage — verify sensor, wiring, and module.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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