Idle, Speed and Auxiliary System Codes

Codes for idle control, the vehicle speed sensor, cruise control and some auxiliary systems such as coolant temperature and the thermostat.

A rough or high idle usually has a simple mechanical cause: a dirty throttle body or an air leak. Vehicle speed codes also affect the speedometer, automatic transmission shifts and stability control.

Most searched codes in this system

• P0505 to P0507: idle control out of range.
• P0500 to P0503: vehicle speed sensor.
• P0128: coolant does not reach thermostat temperature.
• P0562 and P0563: system voltage low or high.

What to check first

1. Clean the throttle body and run the idle relearn if the manufacturer requires it.
2. Look for air leaks after the throttle plate.
3. Check the thermostat if the engine takes a long time to warm up.
4. Measure the charging voltage: 13.5 to 14.7 V with the engine running.