Malfunction Indicator Lamp (MIL) Inoperative

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Schematic:

CIRCUIT DESCRIPTION
When the ignition is turned ON, the Malfunction Indicator Lamp (MIL) will momentarily flash ON then OFF and remain ON until the engine is running, if no Diagnostic Trouble Codes (DTCs) are stored. The Powertrain Control Module (PCM) controls the MIL by providing a ground path through the MIL control circuit to turn ON the MIL.

DIAGNOSTIC AIDS
An open ignition fuse wilt cause the entire cluster to be inoperative, and may set DTCs P1629 and U1016.

Inspect the battery and the ignition positive voltage circuits for faulty connections if the MIL is intermittent.

Any circuitry that is suspected of causing an intermittent complaint should be thoroughly inspected for:
^ Backed-out terminals
^ Improper mating
^ Broken locks
^ Improperly formed or damaged terminal
^ Faulty terminal-to-wiring connections
^ Physical damage to the wiring harness

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
1. The Powertrain (OBD) System Check prompts you to complete some of the basic checks and to store the Freeze Frame and Failure Records data on the scan tool, if applicable. This creates an electronic copy of the data that was captured when the malfunction occurred. The scan tool stores this data for later reference.
3. Connections that are suspected of malfunctioning should be thoroughly inspected as described in the diagnostic aids.
4. If the engine fails to start and the MIL is inoperative, then the malfunction can be isolated to one of the following items:
^ An open PCM ignition positive voltage circuit
^ An open battery positive voltage circuit
^ A faulty ground at the engine block
^ A malfunctioning PCM
5. Probing the MIL circuit with a test lamp to a ground simulates the PCM's control of the MIL. If the MIL illuminates, then the malfunction can be isolated to the control of the MIL or to a faulty electrical connection at the MIL terminal to the PCM. Electrical connections that are suspected of malfunctioning should be thoroughly inspected as described in the diagnostic aids.
7. It takes very little resistance for the battery and the ignition 1 feed circuits to cause an intermittent condition. The battery and the ignition 1 feed circuits should also be inspected for electrical connections as described in diagnostic aids.
11. A shorted MIL circuit can be diagnosed with a scan tool.
12. An open MIL circuit can be diagnosed with a scan tool.
13. Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Techline(TM) information for PCM programming.
14. If no malfunctions are present at this point and no DTCs were set, refer to the diagnostic aids for additional checks and information.