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Home >> Buick >> 1994 >> Roadmaster Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Testing >> Diagnostic Circuit Check >> A-2, Mil On Steady Or Won't Flash Code 12
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A-2, Mil On Steady Or Won't Flash Code 12

  1. Start engine. Check MIL. If MIL is not flashing, go to next step. If MIL is flashing, turn ignition off. Disconnect PCM connector "D". Using test light connected to battery voltage, probe DLC test terminal "B". See Figure . If test light illuminated, output/field service enable circuit (12-pin DLC terminal "B") is shorted to ground. If test light did not illuminate, replace faulty PCM.
  2. Connect DVOM between ground and DLC output/field service enable terminal (12-pin DLC terminal "B"). DVOM should read 5 volts. If reading is as specified, check for faulty PCM connection or faulty PCM. If reading is not as specified, go to next step.
  3. Turn ignition off. Disconnect PCM connector"D". Using jumper wire, ground DLC test terminal "B". With test light connected to battery positive, probe PCM harness connector terminal D20 (White/Black wire). Test light should illuminate. If test light illuminated, check for faulty PCM connection or faulty PCM. If test light did not illuminate, DLC test terminal "B" circuit is open.
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