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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 85 (Generator & Regulator) >> Self-Diagnostic System >> On-Board Diagnostics >> MIL Diagnostic Mode

MIL Diagnostic Mode

WARNING: This page is about a different car, the 1995 Dodge Ram Wagon, 1995 Dodge Ram Van, 1995 Dodge Pickup, and 1995 Dodge Cab & Chassis. 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. Refer to the following list.
  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 TESTING - ON-VEHICLE .
    CHARGING SYSTEM TROUBLE CODES

    Fault Code Circuit 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: Refer to the following list.