Code
C0155
Generic
C — Chassis
Wheel Speed Sensor Circuit Fault (Sensor 1)
Views:
UK: 2
EN: 7
RU: 7
AI status
Completed
Completed
100%
Causes
- Damaged or failed wheel speed sensor (sensor 1)
- Open, shorted or chafed wiring between sensor and ABS module
- Corroded or loose sensor connector or pins
- Contaminated, broken or missing tone ring (reluctor) or excessive air gap
- Short to voltage or ground from a nearby damaged circuit
- Faulty ABS/traction control module or internal input driver
Symptoms
- ABS warning light and/or traction control light illuminated
- Loss or reduced function of ABS/ESC/traction control
- Inconsistent wheel speed reading on scan tool for sensor 1 (stuck at zero or erratic)
- Possible ABS activation at low speed or unavailable ABS
- Cruise control may be disabled or speedometer issues on some vehicles (if speed input used)
What to check
- Read ABS module fault code(s) and live data with a scan tool. Note freeze-frame data and stored events.
- Compare wheel speed values: sensor 1 versus opposite wheel while wheel is rotated.
- Visually inspect sensor, connector and wiring for damage, corrosion, chafing or pin push-out.
- Backprobe connector: check supply/reference voltage (if active sensor), ground, and signal while rotating wheel.
- Measure sensor resistance (passive type) with ohmmeter and compare to specification.
- Inspect tone ring for missing/broken teeth, heavy rust, metal debris or excessive air gap.
Signal parameters
- Passive (VR) sensor resistance typically in the range ~700–1500 ohms (varies by vehicle) — consult OEM spec
- When wheel is rotated, passive VR sensor should produce an AC voltage that increases with speed (tens of mV at very low speed to several hundred mV or more at higher speed)
- Active (Hall/IC) sensor: reference supply typically 5V (or 12V on some designs) and output is a digital square wave 0–5V (or switching to ground) with frequency proportional to wheel speed
- Open-circuit: infinite resistance; short to ground/voltage: near 0 ohms or constant supply voltage on signal line
- Typical frequency range: low Hz at crawling speed up to hundreds of Hz at higher road speeds (varies by tooth count)
Diagnostic algorithm
- Retrieve all ABS/traction codes and freeze-frame data with a scan tool. Note which wheel is labeled sensor 1 (consult vehicle-specific mapping).
- Visually inspect the sensor, tone ring, and harness for damage, debris, or corrosion. Repair obvious mechanical issues.
- With the connector disconnected, measure sensor resistance (for passive sensors). Replace if open or out of spec.
- For active sensors, reconnect and backprobe: verify reference supply voltage and ground with ignition on. Replace sensor if supply is correct but no signal present.
- Spin the wheel or rotate tone ring while watching live data or using an oscilloscope: look for clean pulse waveform (digital) or AC sine waveform (VR). Compare amplitude and frequency to opposite wheel.
- Check continuity and insulation of sensor wiring from connector to ABS module; repair any opens, shorts, or high-resistance joints. Pay attention to common failure points (strut, knuckle, harness clamps).
- Inspect tone ring runout and tooth condition; remove debris or replace damaged ring/assembly as needed.
- If sensor, wiring, and tone ring are good but fault persists, verify ABS module input circuits and grounds. Probe at the ABS module connector for signal; consider module fault if wiring good and sensor signals absent.
- After repairs, clear codes and perform a road test or wheel spin test to confirm code does not return and ABS functions normally.
Likely causes
- Moisture-corroded connector at the sensor
- Wire harness rubbed through at strut/knuckle causing intermittent open
- Sensor damaged by impact or road debris
- Missing/broken teeth on tone ring or magnetic debris on ring
- Connector pin pushed out or bent causing poor contact
Fault status
Status
Wheel Speed Sensor Circuit Fault — ABS control module indicates invalid/absent signal from wheel speed sensor 1 (open, short, or out-of-range signal).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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