Hot Light Or Coolant Temperature Light
- Turn ignition on and note indicator light. Light should be on as a bulb check. If light is not on, go to step 2). Start engine. Light should go off. If light stays on and engine temperature is low, scan coolant temperature sensor reading. If reading indicates a false high reading, see COOLANT TEMPERATURE SENSOR in this article. If reading is low, check for a short in the bulb ground circuit. If short is not present, connect a test light to battery voltage and touch ECM temperature light driver terminal. If test light illuminates, ECM is faulty.
- Disconnect ECM connector containing temperature light driver terminal. Turn ignition on. Using a jumper wire, ground ECM temperature light driver terminal. If light does not illuminate, check for an open in the temperature light circuit, including a bad bulb. If light does illuminate, ECM driver is faulty.