C0038 indicates the ABS/ESC system has detected a fault in the voltage supply circuit to the left rear wheel speed sensor. This means the sensor is not receiving the reference voltage it needs to operate, or the circuit has an abnormal voltage condition. The code points to an electrical problem in the supply line rather than a weak sensor signal.
The sensor can develop an internal open or short that disrupts the supply voltage circuit, causing the ABS module to detect an out-of-specification condition on the supply line.
Road debris, corrosion, or flexing at the rear suspension can damage the harness, creating an open or short-to-ground in the voltage feed to the sensor.
Moisture and salt intrusion at the in-line or sensor connector can increase resistance or cause intermittent loss of supply voltage to the left rear sensor.
A compromised ground circuit for the sensor can alter current flow and voltage levels, leading the control module to flag a supply-side circuit error.
In rare cases, the module’s internal voltage driver for the left rear sensor circuit fails; this should only be considered after the sensor, wiring, and connectors are proven fault-free.
Base braking remains functional, but ABS and stability control may be disabled. You should diagnose and repair the fault promptly, especially in adverse weather.
Not necessarily. C0038 specifically relates to the supply voltage circuit that feeds the sensor, which is separate from the signal or tone-wheel circuit.
No. The sensor and its wiring are the most common causes. Module failure is uncommon; replacing a control module before verifying the sensor and harness is usually an unnecessary expense.
A severely worn bearing can allow the sensor to contact the reluctor ring and fail electrically, but the code itself reflects a supply circuit fault. Check for physical damage if bearing play is excessive.