Hot Light Diagnosis
NOTE:
These checks assume vehicle is not actually overheating. Verify proper operation of cooling system prior to diagnosing hot light.
Hot light is powered by the 10-amp INDIC fuse. Light will turn on when ECM provides a ground for the circuit. If circuit grounds between light and ECM, light will illuminate any time the ignition is turned on.
- Turn ignition on with engine off (bulb test position). If hot light illuminates, go to step 3. If hot light toes not illuminate, check the following:
- 10-amp INDIC fuse
- Faulty instrument cluster bulb
- Open circuit between fuse and hot light
- Backprobe terminal YC9 at ECM with a test light to battery voltage. Turn ignition on. If test light does not illuminate, ECM terminal connection is bad or ECM is faulty. If test light illuminates, turn ignition off. Disconnect ECM connectors. Jumper terminal YC9 to ground. Turn ignition on. If hot light does not illuminate, check for open circuit between hot light and ECM. If light does not illuminate and all circuits are intact and power is available to light, instrument cluster must be replaced.
- Start engine. If test light goes off, no problem is evident. See DIAGNOSTIC AIDS. If test light is on, turn ignition off. Disconnect ECM connector. Probe ECM harness terminal TC9 with a test light to battery voltage. If light is off, replace ECM. If light is on, repair short to ground in circuit No. 35. If no short is present, replace instrument cluster.
This determines which circuit is out of specification. All circuits except SERVICE ENGINE SOON light and hot light should have battery voltage with engine running and ALDL test terminal "B" not grounded.