C1370

Code

Generic C — Chassis

ABS wheel speed sensor circuit fault

Brand: Generic

Type: C — Chassis

Views: UK: 18 EN: 25 RU: 15

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Damaged or corroded wheel speed sensor connector or wiring
Open or short circuit in sensor wiring (chafing, pinched, broken wire)
Failed wheel speed sensor (passive or active type)
Faulty tone ring/reluctor (missing, cracked, excessive air gap, or magnetic contamination)
Poor ground or supply voltage to the sensor/ABS module
Faulty ABS control module or internal driver circuit

ABS warning lamp and/or traction/stability lamp illuminated
Loss or intermittent operation of ABS and traction control
Unusual brake pedal feel or ABS activation when not expected
Inoperative or erratic speedometer (on some vehicles)
Possible diagnostic trouble codes for wheel speed sensors or ABS module communication

Scan vehicle with a compatible scan tool; record C1370 and any other ABS/communication codes and freeze frame data
Visually inspect sensor, connector, and wiring harness at the affected wheel for damage, corrosion or water ingress
Check tone ring (reluctor) for missing/chipped teeth, heavy corrosion or excessive air gap
Backprobe sensor connector and check for proper supply/reference voltage and ground (if active/Hall sensor)
Measure sensor resistance with ohmmeter (for passive sensors) and compare to service spec
Use a scope or AC voltmeter to observe sensor waveform while wheel is rotated — look for clean sine/square pulses without dropouts

Passive (magnetic) sensor: DC resistance typically ranges widely (≈800–4000 Ω depending on design); produces AC voltage output that increases with wheel speed (tens of mV at very low speed up to several volts at higher speed)
Active (Hall/VR with electronics): requires ~5 V reference and ground; signal is a square wave 0–5 V (or 0–12 V depending on vehicle) with frequency proportional to wheel speed
Pulse frequency and pulses-per-revolution vary by vehicle — consult service manual for tone ring tooth count and expected Hz at test speed
Typical expected waveform: consistent amplitude and frequency with no dropouts, no prolonged zero or constant voltage during rotation

Retrieve all codes and freeze-frame data with scan tool; note vehicle speed, conditions, and any other codes.
Visually inspect affected wheel sensor, harness, connector and tone ring for damage, debris, or corrosion. Repair physical damage before electrical testing.
With ignition on (engine off), backprobe sensor connector: for active sensors verify reference voltage (≈5 V) and ground; for passive sensors measure resistance across sensor leads and compare to spec.
Spin wheel by hand (or raise vehicle safely and rotate wheel) while monitoring live wheel speed data from scan tool — note if sensor reports speed and if values are steady.
Using an oscilloscope (preferred) or an AC voltmeter (for passive sensors), observe waveform while wheel is rotated; look for clean repetitive pulses and no dropouts. Wiggle wiring to detect intermittent faults.
If reference and ground are present but no signal, substitute known-good sensor or bench-test suspect sensor to confirm failure.
Inspect wiring continuity from sensor connector to ABS module; check for shorts to battery or ground and repair as needed.
Inspect tone ring for missing/chipped teeth or excessive air gap; replace or correct alignment as required.
If wiring and sensor test good, check ABS module power/ground and input driver circuits; consider module fault if module input is not responding or shows internal fault.
Clear codes and perform test drive to confirm repair; re-scan to ensure code does not return.