Malfunction Indicator Lamp Circuit Check

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

When the ignition switch is initially turned to the run position, the Malfunction Indicator Lamp (MIL) flashes and then remains On. When the engine is running and no Diagnostic Trouble Codes (DTCs) are stored, the Vehicle Control Module (VCM) turns Off the MIL. The ignition switch supplies battery voltage directly to the MIL telltale. The VCM controls the MIL by providing a ground path through the MIL control circuit in order to turn On the MIL.

DIAGNOSTIC AIDS

An open gauge fuse will cause the entire IP cluster to be inoperative.

Check for any circuitry that is suspected of causing an intermittent complaint for the following conditions:

^ Backed out terminals

^ Improper mating

^ Broken locks

^ Improperly formed or damaged terminals

^ Poor terminal to wiring connections

^ Physical damage to the wiring harness

TEST DESCRIPTION

Number(s) below refer to step number(s) on the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data with the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

4. A MIL that responds correctly to the scan tool commands indicates that the fault is not present at this time or that the condition that caused the No MIL condition has been corrected.

5. The MIL should be OFF. This step checks for a short to ground in the MIL control circuit by removing the VCM from the circuit.

7. This step checks for the MIL control circuit for a short to B+.

9. The power and ground circuits for the VCM and MIL control are OK. The VCM is probably faulty.

10. VCM grounds will only cause a problem if all of the grounds are not making a good connection. If a VCM ground problem is suspected, the most probable place to check is where all the grounds meet, at the engine block.

12. If the fuse is open, check for a short to voltage on the circuit between the VCM and the MIL bulb.

15. For MIL bulb replacement procedures, refer to Electrical Diagnosis.

17. For IP replacement procedures, refer to Electrical Diagnosis.

19. The scan tool can communicate with the VCM; therefore, the serial data circuit is OK. If the VCM connections are OK, the VCM is probably faulty.

20. Locate and repair any shorts that may have caused the fuse to open before replacing the fuse.