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Service Engine Soon Indicator Stays On At All Times Or Inoperative

NOTE: To prevent any misdiagnosis, zero DVOM before taking any measurements.
  1. If SERVICE ENGINE SOON indicator continuously illuminates, go to next step. If SERVICE ENGINE SOON indicator does not continuously illuminate, go to step  8 .
  2. Connect scan tool. Using scan tool, check for instrument cluster DTCs. If no DTCs exist, go to next step. If any DTCs exist, go to SELF-DIAGNOSTIC SYSTEM  .
  3. Disconnect Powertrain Control Module (PCM) Clear 80-pin connector C2. Start engine, and allow it to idle. If SERVICE ENGINE SOON indicator illuminates, go to next step. If SERVICE ENGINE SOON indicator does not illuminate, go to step  7 .
  4. Turn ignition switch to OFF position. Disconnect instrument cluster Gray 24-pin connector. Using DVOM, check resistance between instrument cluster harness connector terminal B5 (Brown/White wire) and ground. If resistance is 0-3 ohms, go to next step. If resistance is not 0-3 ohms, go to step  6 .
  5. Repair short to ground in Brown/White wire between instrument cluster and PCM connector C2. Recheck system operation.
  6. Replace instrument cluster. See INSTRUMENT CLUSTER  under REMOVAL & INSTALLATION. Recheck system operation.
  7. Check for poor connections at PCM. Repair as necessary and recheck system operation. If connections are okay, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. Recheck system operation.
  8. If SERVICE ENGINE SOON indicator is inoperative when ignition switch is in RUN position and engine is not running, go to next step. If SERVICE ENGINE SOON indicator operates when ignition switch is in RUN position and engine is not running, system is operating properly.
  9. Disconnect Powertrain Control Module (PCM) Clear 80-pin connector C2. Connect a 3-amp fused jumper wire between PCM harness connector C2, terminal No. 5 (Brown/White wire) and ground. If SERVICE ENGINE SOON indicator illuminates, go to step  7 . If SERVICE ENGINE SOON indicator does not illuminate, go to next step.
  10. Turn ignition switch to OFF position. Leave jumper wire connected as specified in step 9)  . Disconnect instrument cluster Gray 24-pin connector. Using DVOM, check resistance between instrument cluster harness connector terminal B5 (Brown/White wire) and ground. If resistance is 0-3 ohms, go to step  6 . If resistance is not 0-3 ohms, go to next step.
  11. Repair poor connection, open or short to voltage in Brown/White wire between instrument cluster and PCM connector C2. Recheck system operation.
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