Anti-lock brakes not working? It might be a broken vehicle speed sensor

20120911032504CEL_AmberYour car’s “Check Engine” or “Service Engine Soon” light can flash on for more than 1,400 different reasons, and in the coming months, we’re going to share with you what some of those reasons are. The light is part of your vehicle’s on-board diagnostics (OBD) system and can indicate anything from a quick fix like a loose gas cap to a major repair like a catalytic converter.

Trouble code: P0500

This means the vehicle speed sensor is not reading the vehicle’s speed correctly.

Symptoms of a P0500 IAC Malfunction may include:

  • Loss of anti-lock brakes.
  • The “anti-lock” or “brake” warning lamps on the dash may be lit (in addition to the check engine light).
  • The speedometer or odometer may not work properly (or at all).
  • Your vehicle’s RPM limiter may be decreased.
  • The shifting of an automatic transmission may become erratic.

Potential causes of a P0500 code include:

  • The vehicle speed sensor is not functioning properly.
  • There is a broken/frayed wire leading to the vehicle speed sensor.
  • The vehicle’s powertrain control module is not correctly configured for the actual tire size on the vehicle.

Possible solutions

  • Reset the code and see if it comes back.
  • Check all wiring and connectors that lead to the speed sensor.
  • Check the voltage at the speed sensor.
  • If everything looks OK, replace the sensor.
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