C0038 — Left Rear Wheel Speed Sensor Supply (Subfault)

OBD2 code C0038 flags a problem with the ABS / stability control (C0038 — left rear wheel speed sensor supply (subfault): causes, symptoms & fix). Short, gentle driving to a shop is usually possible. Common culprits: failed wheel speed sensor, blown fuse or low voltage to the ABS module, damaged tone (reluctor) ring on the hub.

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Is it safe to drive?

Drive with caution The base brakes usually still work, so careful driving is possible — but ABS and stability control are disabled, which lengthens stopping distances on slippery roads. Fix promptly and avoid harsh driving.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm C0038 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many C0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the ABS / stability control for damage, corrosion, chafing or poor contact.
Subsystem check Read all four wheel speed PIDs while driving slowly — the faulty sensor drops out or reads implausibly.
Subsystem check Inspect the sensor and tone ring for metal debris and damage near the hub.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm C0038 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for C0038 (parts and labor, USD, independent shop rates): ABS module repair or replacement: $400–$1,200; Replace a wheel speed sensor: $120–$350; Repair sensor wiring: $80–$250. Overall, fixing C0038 usually costs between $80 and $1,200. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What are the symptoms of C0038?

Drivers most often notice: ABS not operating during hard braking, brake pedal pulsation changes, stability control disabled message, ABS or ESC warning light on.

How much does it cost to fix C0038?

ABS module repair or replacement — $400–$1,200; Replace a wheel speed sensor — $120–$350; Repair sensor wiring — $80–$250. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Is it safe to drive with C0038?

The base brakes usually still work, so careful driving is possible — but ABS and stability control are disabled, which lengthens stopping distances on slippery roads. Fix promptly and avoid harsh driving.

What does OBD2 code C0038 mean?

How do I diagnose C0038 myself?

Start with a scan: confirm C0038, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the ABS / stability control, and verify the suspect component against live data before buying parts.

C0038 — C0038 — Left Rear Wheel Speed Sensor Supply (Subfault): Causes, Symptoms & Fix

When your vehicle's anti-lock braking system detects that something is wrong with the electrical supply feeding the left rear wheel speed sensor, it logs code C0038. This particular fault means the ABS module is not receiving the expected voltage or signal from that sensor circuit. The wheel speed sensors work alongside the ABS controller to monitor how fast each wheel is rotating; if any sensor fails to deliver reliable data, the system disables its protective functions to prevent unpredictable behavior. C0038 specifically points to a supply-side problem — the power or ground that the sensor needs to operate — rather than a mechanical issue with the sensor itself.

The affected system is the family of stability and braking aids that rely on wheel speed information. These include ABS, electronic stability control (ESC), and often traction control. Each corner of the vehicle has its own speed sensor, and the ECU cross-checks their readings to detect wheel slip or rotation anomalies. When C0038 sets, the module has confirmed the fault condition multiple times under specific driving circumstances before activating the dashboard warning light. The freeze frame data stored alongside C0038 records engine load, RPM, coolant temperature, and vehicle speed at the moment of detection — use those figures to replicate the failure scenario during diagnosis.

Symptoms of C0038

ABS fails to activate during emergency or hard braking, so the brakes may lock up instead of pulsing
Brake pedal pulsation feels different or stops entirely during hard stops
Dashboard displays a stability control disabled or ESC warning message
ABS or ESC warning light stays illuminated after starting the vehicle
Speedometer reads erratically or cruise control refuses to engage

Common Causes of C0038

Damaged or corroded wiring in the left rear wheel speed sensor circuit
Blown fuse or insufficient voltage reaching the ABS module
Failed wheel speed sensor with internal open or short circuit
Loose or corroded electrical connector at the sensor or ABS unit
Faulty ABS control module unable to regulate sensor supply voltage
Tone ring (reluctor ring) on the rear hub bearing damaged or contaminated with debris

Diagnosing C0038 Step by Step

Connect an OBD2 scanner and confirm C0038 is present in the ABS module. Record the freeze frame data — it shows exactly what engine and vehicle conditions existed when the fault was detected.
Pull all related DTCs from every module. Side faults in the same circuit often point to the root cause, and some vehicle manufacturers have technical service bulletins addressing specific C0038 patterns.
Perform a hands-on inspection of the left rear wheel speed sensor harness. Look for cracked insulation, broken strands of wire, chafing from road debris, and any moisture or corrosion at the connector. Wiggle the wiring while monitoring live sensor data to expose intermittent opens.
Measure voltage at the sensor connector with the key on. Compare your readings to manufacturer specifications — the ABS module should be supplying the correct reference voltage.
Remove the sensor and check its magnetic tip for metal shavings, cracks, or physical damage. Inspect the tone ring attached to the hub for missing, bent, or contaminated teeth.
Clear the codes and complete a full drive cycle that reproduces the freeze frame conditions. If C0038 returns, the fault is confirmed and not intermittent.

Repair Options and Costs

Wiring repair for the sensor circuit typically runs $80–$250 depending on the extent of the damage and whether connectors need replacement. A complete wheel speed sensor replacement for the left rear corner generally costs $120–$350 including parts and labor at an independent shop. If the ABS module itself is at fault, repair or replacement ranges from $400–$1,200 depending on whether you choose a rebuilt unit, a new module, or dealer programming of an existing unit.

Total Cost to Fix C0038

The total expense hinges entirely on which component is actually responsible for the supply fault. Most situations involving C0038 are resolved through wiring repairs or a single sensor replacement, putting the bill in the $150–$350 range. The worst-case scenario — an internal ABS module failure — can stretch to $1,200 or beyond. Always verify the exact failing part before committing to the most expensive repair path.

Can You Drive with C0038?

The ordinary friction brakes remain functional, so you can still stop the vehicle. However, ABS and electronic stability control are disabled, meaning wheels can lock up on slick surfaces and the vehicle loses its ability to correct skidding. This is not a code to ignore or delay. Drive cautiously, avoid high-speed travel and wet or icy roads, and schedule the repair as soon as possible.