A-1, SERVICE ENGINE SOON LIGHT INOPERATIVE

1. If SERVICE ENGINE SOON light does not illuminate with ignition on and engine off, attempt to start engine. If engine starts, go to step 3). If engine does not start, check fusible links at battery. Also check ECM fuse. If fusible links or ECM fuse are blown, repair short to ground.

2. If fusible links and ECM fuse are okay, turn ignition on, and check power circuits to ECM, including keep-alive memory and ignition feed. If power is not available to power terminals of ECM, check for opens in power circuits. If power is available to ECM power terminals, check for poor ECM ground circuits. If circuits are okay, replace faulty ECM.

3. If engine starts and SERVICE ENGINE SOON light does not illuminate, turn ignition off. Disconnect ECM connectors. Turn ignition on, and jumper ECM SERVICE ENGINE SOON light driver terminal to ground using a test light.

4. If light is now on, repair light driver terminal connections at ECM or replace faulty ECM. If light stays off when test light is used to ground light driver terminal, check for blown instrument panel fuse, faulty bulb, open in light driver circuit between ECM and bulb, short in driver circuit to voltage or open in ignition feed to SERVICE ENGINE SOON light.

Answered by KHLow2008 (expert)
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