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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 83 (Generator & Regulator) >> Self-Diagnostic System >> On-Board Diagnostics >> MIL Diagnostic Mode

MIL Diagnostic Mode

WARNING: This page is about a different car, the 1995 Plymouth Voyager, 1995 Plymouth Grand Voyager, 1995 Dodge Grand Caravan, 1995 Dodge Caravan, and 1995 Chrysler Town & Country. However, it is still accessible from the selected car via links, so may be relevant.
  1. Start engine (if possible). On A/T models, move transmission shift lever through all positions, ending in Park. On all models, turn A/C switch on and then off (if equipped).
  2. Turn engine off. Without starting engine again, turn ignition on, off, on, off and on. MIL will come on for 2 seconds as a bulb check, followed by fault codes. Record 2-digit fault codes displayed by MIL.
  3. For example, Code 23 is displayed as flash, flash, pause, then flash, flash, flash. Fault codes are displayed in numerical order and are separated by 4-second pause.
  4. Once MIL begins flashing fault codes, cycle cannot be stopped. To enter diagnostic mode again, repeat step 1). Code 55 indicates end of fault code display. For more information on self-diagnostics, see appropriate G - TESTS W/ CODES article in ENGINE PERFORMANCE section:
    • G - TESTS W/CODES - 2.5L
    • G - TESTS W/CODES - 3.0L
    • G - TESTS W/CODES - 3.3L GASOLINE
    • G - TESTS W/CODES - 3.3L CNG
    • G - TESTS W/CODES - 3.8L
  5. After retrieving fault codes, refer to CHARGING SYSTEM FAULT CODES table to identify problem circuit (same description is displayed on DRB). Test appropriate circuit, and repair or replace components as necessary. See appropriate test procedure under ON-VEHICLE TESTING.
    CHARGING SYSTEM TROUBLE CODES

    Code Description MIL On?
    12 Battery Feed To PCM No
    41 (1) Generator Field Control Yes
    44 (1) Battery Temp. Sensor Yes
    46 (1) High Battery Voltage Yes
    47 (1) Low Battery Voltage Yes
    55 End Of Diagnostic Mode No
    (1) This code will cause limp-in mode.
    NOTE: Only charging system-related codes are listed. For engine-related codes, see appropriate G - TESTS W/ CODES article in ENGINE PERFORMANCE section:
    • G - TESTS W/CODES - 2.5L
    • G - TESTS W/CODES - 3.0L
    • G - TESTS W/CODES - 3.3L GASOLINE
    • G - TESTS W/CODES - 3.3L CNG
    • G - TESTS W/CODES - 3.8L