Code 45, Idle Switch Circuit Grounded Or MISADJUSTED

This code will set if ECM sees an open switch or circuit at idle conditions. When properly adjusted, the TPS idle switch will pull ECM circuit low (to ground) when throttle is closed. If idle switch is measured separately, it will show little or no resistance when closed. When throttle is opened, the circuit will go high at the ECM. If idle switch is measured separately, it will show open or infinite resistance.

1. With throttle wide open, TPS idle switch should be open.
2. This checks for TPS harness shorted to ground at throttle body.
3. This checks for short to ground or circuits shorted together on ECM side of TPS connector.

Fig 1: Code 45, Circuit Wiring Diagram & Flow Chart

Courtesy of GENERAL MOTORS CORP.