Check as follows: 1 Disconnect the Optimized Idle Thermostat connector. 2 Inspect the sensor harness for bent, spread, or corroded pins. 2a If damage is found, repair as necessary. 2b If no damage is found, Go to step 3.
3Turn the key to the on position, engine off.
4Measure the voltage between pin 5 of the Optimized Idle Thermostat harness side connector, and ground. Is the voltage within 1.5 volts of battery voltage.
4a Yes, Go to step 5. 4b No, repair the circuit short between pin 5 of the Optimized Idle Thermostat connector and ignition feed.
5.Measure the resistance between pin 6 of Optimized Idle Thermostat harness side connector and ground. Is the resistance greater than 5 ohms?
5a Yes, repair the open circuit between pin 6 of Optimized Idle Thermostat connector and vehicle ground. 5b No, replace the Optimized Idle Thermostat.