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Home >> Oldsmobile >> 1994 >> Achieva SL, 2.3 D >> 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. Turn ignition on, engine not running. Check Malfunction Indicator Light (MIL). If MIL is on go to next step. If MIL is off, refer to A-1, MIL INOPERATIVE.
  2. Ground diagnostic test connector "B". See Figure. If MIL did not flash Code 12, go to next step. If MIL flashed Code 12, check serial data circuit No. 461 (Orange wire) for open or short to ground between DLC and PCM. If circuit is okay, check for faulty PROM or PCM.
  3. Turn ignition off. Disconnect PCM connectors. Turn ignition on. If MIL came on, repair short to ground in circuit No. 419 (Brown/White wire) to PCM. If MIL did not come on, go to next step.
  4. Turn ignition off. Reconnect PCM connectors. Turn ignition on, engine off. Ensure DLC test terminal is not grounded. Using test light connected to ground, backprobe PCM circuit No. 451 (White/Black wire). If MIL did not flash Code 12, go to next step. If MIL flashed Code 12, check for open in circuit No. 451 (White/Black wire) between DLC and PCM. If circuit is okay, check for open between DLC test terminal "A" and ground.
  5. Check PROM for proper installation. If okay, replace PCM using original PROM. Recheck for Code 12. If Code 12 is now present, system is okay. If Code 12 is still not present, replace PROM.
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