P0500: OBD-II code P0500 flags a fault in the vehicle speed sensor circuit — the PCM is losing the speed signal used for shifts, cruise control, and the speedometer.

Symptoms

• The speedometer reads zero or fluctuates erratically while driving, and the odometer may stop counting mileage.
• Cruise control refuses to engage or drops out mid-drive, and the transmission may shift harshly or hold gears longer than usual.
• The ABS and traction control warning lamps can also illuminate if they share the same wheel/vehicle speed input.

Common causes

• A failed vehicle speed sensor (VSS) mounted on the transmission — most common on older non-CAN vehicles.
• On newer vehicles, a fault on the ABS wheel-speed circuit or the CAN bus link between the ABS module and the PCM.
• Damaged wiring or a corroded connector at the VSS, or a stripped drive gear inside the transmission housing.

What to do?

On older cars, test the VSS with a DMM (AC voltage while spinning the driveshaft) or replace and retest. On newer CAN-based cars, scan every module for U-codes and ABS wheel-speed codes and fix those first. Inspect wiring at the sensor for oil, corrosion, or damage. Replace the sensor or repair wiring as needed.