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Home >> Oldsmobile >> 1995 >> Achieva SC, 2.3 D, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Testing >> Diagnostic Circuit Check >> A-2, Mil On Steady Or Won't Flash Code 12 >> 2.3L
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A-2, Mil On Steady Or Won't Flash Code 12: 2.3L

  1. Install Tech 1 scan tool to Data Link Connector (DLC). Turn ignition on, with engine off. Check Malfunction Indicator Light (MIL). If MIL is on, go to next step. If MIL is off, see A-1, MIL INOPERATIVE  .
  2. Observe Tech 1 scan tool display for scan data. Is scan data displayed? If yes, go to next step. If no DLC or scan data is displayed, check serial data circuit (Tan wire) for open, short to ground or short to voltage. See WIRING DIAGRAMS  . Repair as necessary. If serial data circuit is okay, replace faulty PCM or EPROM.
  3. Using scan tool, command MIL on and off. Does MIL turn on and off when commanded? If no, go to next step. If yes, check for DTCs. If DTC(s) is present, diagnose affected DTC(s). Refer to appropriate SELF-DIAGNOSTICS article. If no DTC(s) is present, system is okay.
  4. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Observe MIL. If MIL is off, repair short to ground in MIL circuit (Brown/White wire) to PCM connector. See WIRING DIAGRAMS  . If MIL is on, go to next step.
  5. Turn ignition off. Check EPROM for proper installation. If installation is okay, replace PCM using original EPROM. Turn ignition on, with engine off. Using scan tool, command MIL on and off. If MIL turns on and off as commanded, system is okay. If MIL does not turn on and off as commanded, replace EPROM.
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