Code
C1156
Other
C — Chassis
Speed Wheel Sensor LF Circuit Open
Views:
UK: 18
EN: 25
RU: 24
AI status
Completed
Completed
100%
Causes
- Broken or disconnected wiring between LF wheel speed sensor and ABS module
- Corroded or loose sensor connector or terminals
- Failed/defective LF wheel speed sensor (internal open)
- Damaged sensor tone ring or hub that prevents signal generation
- Poor ground or blown fuse affecting sensor power/reference (for active sensors)
- Intermittent connector contact from water/road contamination
Symptoms
- ABS and/or traction control warning lamp illuminated
- Possible speedometer or cruise control issues (in some vehicles)
- ABS may not engage or may behave incorrectly under braking
- Traction/stability control disabled or limited
- Diagnostic trouble code C1156 stored in ABS/traction control module
What to check
- Scan ABS module for stored codes and freeze frame data; note status bits
- Perform a careful visual inspection of LF wheel sensor, tone ring, harness and connector
- Check for corrosion, bent pins, water intrusion or broken wires at the connector
- Wiggle wiring and connector while monitoring live wheel speed data for dropouts
- Measure continuity between the sensor connector and the ABS module harness connector
- Measure sensor resistance and compare to specification (or compare with same-side/right-front sensor)
Signal parameters
- Passive (magnetic) sensor: typical resistance range ~800–2500 Ω (varies by vehicle) — produces AC voltage when wheel spins (0.1–2.0 Vrms at low speed). Verify OEM spec.
- Active (Hall) sensor: reference supply typically ~5 V (check with key ON), signal toggles between ~0–5 V when wheel rotates. Open circuit may show no output or no reference.
- Continuity: near 0 Ω between sensor housing ground and chassis ground (if sensor ground is separate); otherwise no open between sensor pins and module pins.
- If circuit is open: infinite resistance between sensor terminals or between sensor and module connector.
Diagnostic algorithm
- Retrieve and record all stored codes and live data from the ABS module; note LF wheel speed reading with ignition ON and while driving slowly.
- Visually inspect the LF sensor, tone ring, harness routing, and connector for damage, corrosion, or disconnection.
- With vehicle safely supported, unplug the LF sensor connector. Check for corrosion, pushed-back pins or water. Repair or clean as needed.
- Use a multimeter to measure resistance across sensor terminals. If passive sensor shows open (infinite), replace sensor. If active, check for reference voltage and ground with key ON.
- Check continuity between the sensor connector pins and the ABS module wiring connector pins. Repair any open wires (splice or replace harness) found.
- If wiring is intact, spin the wheel and measure sensor output (AC for passive, pulsed DC for active). No measurable signal indicates sensor or tone ring issue.
- If wiring and sensor check good, inspect tone ring/reluctor for damage or missing teeth and verify correct air gap. Repair or replace hub/reluctor if necessary.
- After repair, clear codes, perform a road test while monitoring wheel speed sensor data to confirm proper operation and that C1156 does not return.
- If the fault persists after sensor and wiring repairs, test or consult procedure for ABS module input driver; consider module diagnosis by a specialist.
Likely causes
- Wiring harness chafed or fractured at suspension pivot or near wheel
- Connector separated or pins pushed back/corroded at sensor
- Sensor damaged by impact, rust, or hub corrosion
- Open internal sensor winding (sensor resistance out of range)
- Short/open in sensor power/reference circuit (for active sensors)
- Connector filled with water or salt causing open circuit
Fault status
Status
Left Front wheel speed sensor circuit open — no valid signal detected from LF wheel speed sensor. ABS/traction control disabled for that input until fault is resolved.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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