C0508 means the ABS or stability-control module has detected a lower-than-expected voltage or signal from the right front wheel speed sensor circuit, often because the circuit is shorted to ground or the sensor itself is failing. The module relies on this signal for anti-lock braking, traction control, and stability control. A 'Circuit Low' code points to the signal voltage dropping below the normal operating range.
The sensor itself is the most common source of a Circuit Low code. Internal wear, coil damage, or a shorted sensor can pull the circuit voltage below the expected threshold.
Chafed, pinched, or melted insulation in the sensor harness can short the signal or power wires to ground. Corroded, loose, or pushed-out connector pins can also cause a low-voltage reading.
A loose sensor, worn wheel bearing, bent axle, or cracked tone ring can weaken the signal amplitude enough that the module interprets it as a low circuit. Physical damage or debris on the sensor tip has the same effect.
Brake dust, road salt, or moisture can degrade the sensor tip or connector terminals, reducing signal strength or creating an unintended path to ground.
The control module that processes the sensor signal can rarely fail internally and misreport a low circuit. This should only be considered after the sensor, wiring, and tone ring have been ruled out.
The vehicle is usually drivable, but ABS, traction control, and stability control may be disabled or operate in a limited failsafe mode. It should be diagnosed and repaired promptly to restore safety systems.
Usually no. The failed sensor, damaged wiring, or connector problem is far more common. Module replacement should only be considered after the sensor circuit and tone ring have been thoroughly tested and ruled out.
A failing wheel bearing can change the sensor air gap and cause erratic speed signals, but the code itself does not prove the bearing is bad. Check the bearing for play and the sensor mounting before replacing it.
That is usually wrong. C0508 is a chassis/ABS circuit code for the right front wheel speed sensor, and the engine computer does not normally process that sensor directly. The fault almost always lies in the sensor, wiring, connector, or — rarely — the ABS/stability-control module.