Circuit Description
There should always be a steady malfunction indicator lamp (MIL) when the ignition is ON and the engine stopped. Battery ignition voltage is supplied directly to the MIL bulb. The electronic control module (ECM) will turn the MIL ON by grounding the ECM connector terminal B10 wire. With the data link connector (DLC) 4, 5, and 6 terminals grounded, the MIL lamp should flash a code 12 followed by any DTCs stored in the ECM memory. A steady MIL lamp suggests a short to ground in the ECM connector terminal B10 wire, or an open in the diagnostic test wire. A steady but dim light would indicate a failed quad-driver. The table will confirm and suggest the cause.
Diagnostic Aids
| • | If the engine runs OK, inspect for a faulty MIL bulb. |
| • | If the engine cranks but will not start, inspect for open fuses and poor ECM connections. Particularly inspect for ECM ignition and battery feeds, including clean and tight ECM ground connections. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Turn ON the ignition. Is the malfunction indicator lamp (MIL) lamp ON? | -- | Go to Step 2 | |
2 |
Does the MIL lamp flash DTC 12? | -- | Go to Step 3 | |
3 |
Is the MIL ON? | -- | Go to Step 4 | Go to Step 5 |
4 | Repair the short to ground in the wire between the ECM connector terminal B10 and the MIL bulb. Did you complete the repair? | -- | -- | |
5 |
Does the MIL flash DTC 12? | -- | Go to Step 6 | Go to Step 8 |
6 | Inspect for an open wire between the ECM connector terminal B9 and the DLC terminal 6. Did you find the condition? | -- | Go to Step 10 | Go to Step 7 |
7 | Repair the open wire between the DLC terminal 4, 5, and ground. Did you complete the repair? | -- | -- | |
8 | Inspect for damage or poor mating at the ECM connector terminal B9. Did you find the condition? | -- | Go to Step 9 | Go to Step 11 |
9 | Repair the ECM connector terminal B9. Did you complete the repair? | -- | -- | |
10 | Repair the wire between the ECM connector terminal B9 and the DLC terminal 6. Did you complete the repair? | -- | -- | |
11 | Replace the electronic control module (ECM). Refer to Engine Control Module Replacement . Did you complete the repair? | -- | -- |
