Code
C1261
LAND ROVER
C — Chassis
Left rear sensor - wheel speed comparison Failure in the power relay circuit of the ABS valve in the detection of disturbances
Views:
UK: 3
EN: 11
RU: 10
AI status
Completed
Completed
100%
Causes
- Faulty or contaminated left‑rear wheel speed sensor
- Damaged or corroded sensor connector or wiring (open, short to ground, short to battery)
- Damaged or missing reluctor/tone ring (wheel bearing or hub damage)
- Intermittent or failed ABS hydraulic valve relay or its power feed (blown fuse, bad relay contacts)
- Poor ground or low supply voltage to ABS module or relay
- Faulty ABS hydraulic control unit or internal relay/electronics
Symptoms
- ABS warning lamp illuminated (may also illuminate traction/stability lamp)
- ABS/traction control may be disabled or operate unpredictably
- Uneven or non‑functional ABS braking at low speeds or during heavy braking
- Possible brake pedal pulsation or changed brake feel
- Diagnostic trouble codes stored for wheel speed comparison and/or relay/power circuits
- Intermittent fault occurrence depending on speed or vibration
What to check
- Read and record all related codes and freeze frame data with a capable scanner
- Check battery voltage and system supply (12V) with engine off and cranking
- Inspect left‑rear wheel sensor, connector, and harness for corrosion, damage, or contamination
- Visually inspect tone ring/reluctor on hub and wheel bearing for damage or missing teeth
- Backprobe sensor connector and measure sensor resistance and AC output while spinning the wheel
- Check continuity and insulation (short to ground/battery) of wiring between sensor and ABS module
Signal parameters
- Wheel speed sensor resistance (typical magnetic sensor): ~800–2000 ohms (varies by design)
- Wheel speed sensor AC voltage output: 0.2–2.0 V AC at low speeds, increasing with wheel speed (hall sensors will show square/digital pulses and a reference voltage)
- Sensor frequency: increases with wheel rpm (check against other wheels at same speed)
- Reference/supply voltage for hall/active sensors: ~5 V or switched 12 V depending on design
- ABS module supply voltage at relay feed: battery voltage (~12 V) with ignition on
- Relay coil control voltage: switched by ABS module (check for proper ground/drive signal when commanded)
Diagnostic algorithm
- Retrieve all stored codes and freeze frame data. Note whether fault is persistent or intermittent.
- Visually inspect left‑rear wheel area: sensor, cable routing, clips, connector, and tone ring for damage or contamination.
- With wheel off the ground, spin wheel and monitor wheel speed live data. Compare left‑rear value to the other three wheels at low speeds. Look for dropouts or inconsistent readings.
- Measure sensor resistance with multimeter and compare to service specification. For active/Hall sensors check reference voltage and signal output while cranking/spinning.
- Backprobe sensor connector while spinning wheel: verify AC/digital signal present and continuous without dropouts.
- Inspect and test ABS fuse(s) and swap/test the ABS valve power relay. Check that the relay receives proper coil drive from ABS module when system activated.
- Check continuity of power feed and ground for the ABS relay and hydraulic valve (look for opens, high resistance, or shorts).
- Wiggle test wiring and connectors while monitoring live data to reproduce intermittent faults.
- If harness, sensor, fuse, and relay are good but fault persists, check ABS module power/ground pins for correct voltages and communication (CAN/serial).
- If module shows internal power/relay faults or communication errors, consider module diagnostics by a specialist and check for available software updates before module replacement.
- Clear codes and road test to verify repair; re‑scan to confirm no recurrence.
Likely causes
- Left‑rear wheel speed sensor fault or damaged tone ring
- Connector/wiring damage at left‑rear sensor or ABS harness
- Faulty or intermittent ABS valve power relay or blown fuse
- Poor ground or low battery/supply to ABS module
- ABS module/hydraulic unit fault (less common)
Fault status
Status
ABS lamp on — left rear wheel speed mismatch with detected disturbance in ABS valve power/relay circuit (power/relay fault detected).
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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