C0038

Code

Generic C — Chassis

Left Rear Wheel Speed Sensor Supply

Brand: Generic

Type: C — Chassis

Views: UK: 23 EN: 46 RU: 30

AI status

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Page language: EN

Causes

Damaged or corroded connector at left rear wheel speed sensor
Broken, pinched, chafed, or shorted wiring between sensor and ABS/BCM
Faulty left rear wheel speed sensor (open/shorted or failed electronics)
Loss of reference supply or ground from ABS control module (blown fuse, bad ground)
Faulty ABS/traction control module or internal driver circuit
Intermittent connection due to water intrusion, bent terminal, or poor crimp

Symptoms

ABS warning lamp and/or traction control/ESP light illuminated
ABS or traction control may be disabled or operate in degraded mode
Possible braking pulsation or reduced ABS function during stops
Inconsistent or zero wheel speed reading for left rear on scan tool
Cruise control or stability control may be disabled
Intermittent faults that can come and go with wheel movement

What to check

Read freeze frame and live data with a scan tool — note left rear wheel speed value vs other wheels
Visual inspection of left rear sensor, harness, and connector for damage, corrosion, or water
Wiggle test harness and connector while monitoring live data for intermittent changes
Check ABS/BCM fuses and module grounds related to sensor supply
Back-probe the sensor connector to check reference supply voltage and ground at rest and while rotating wheel
Measure sensor resistance (for passive sensors) or output signal with wheel rotation

Signal parameters

Active (Hall/3-wire) sensors: reference supply typically ~5 V (±0.5 V). Signal toggles between ~0.5–4.5 V with wheel rotation.
Passive (2-wire) sensors: coil resistance commonly ~500–2,000 ohms (varies by make). Open circuit: >>10 kΩ.
Passive sensor AC output: small mV–V AC that increases with wheel speed (e.g., 0.2–1.5 VRMS at low speeds; higher at speed).
Expected signal frequency proportional to wheel speed: ~tens to hundreds of Hz depending on vehicle and speed.
Short to battery: near battery voltage at sensor signal pin; short to ground: ~0 V at signal/reference pin.

Diagnostic algorithm

Safety: Park on level ground, chock wheels, set parking brake. Use jack stands if wheel removal is required.
Scan tool: Read and record codes and live wheel speed readings. Confirm C0038 present and look for related ABS/traction codes.
Visual: Inspect left rear sensor, tone ring, harness, and connector for physical damage, contamination, or missing teeth on tone ring.
Wiggle Test: With ignition on (engine off) or as directed by scan tool, wiggle harness and connector while monitoring left rear wheel speed value for intermittent changes.
Power & Ground: Back-probe sensor connector. With ignition on, verify reference supply voltage (typically ~5 V) and a good ground. If no supply, inspect fuses and module power/ground.
Resistance/Continuity: With connector disconnected, measure sensor resistance (passive) and compare to spec. Check continuity from sensor pins to ABS module pins, and check for short to ground or battery.
Dynamic Output: Spin the wheel (lift vehicle safely) and observe sensor output on oscilloscope or scan tool. For active sensor expect square/pulse; for passive expect AC waveform whose amplitude increases with speed.
Isolate: If wiring and supply are good but no proper signal, replace the left rear sensor. If a known-good sensor still fails, suspect wiring harness or ABS module driver.
Repair: Repair or replace damaged wiring, connector, sensor, or blown fuse. If ABS module is suspected after wiring and sensor checks, consult manufacturer procedures for module testing/replacement.
Verify: Clear codes, perform a test drive and re-scan to ensure code does not return and the left rear wheel speed reads consistently with other wheels.

Likely causes

Corroded connector or water intrusion at the sensor harness
Open or short in the sensor supply wire caused by suspension movement
Failed wheel speed sensor (common on high-mileage vehicles)
Blown ABS power fuse or bad module ground
Internal ABS module supply/driver fault (less common)

Fault status

⚠️ Status

Left Rear Wheel Speed Sensor Supply: circuit fault detected (open/short/intermittent or supply/ground failure) causing invalid or missing left rear wheel speed input to ABS/traction control module.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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