System Description
The Powertrain On-Board Diagnostic (OBD) System Check must be the starting point for any driveability complaint diagnosis. Perform a careful visual and physical inspection of the Powertrain Control Module (PCM) and engine grounds for being clean and tight. Refer to Visual and Physical Check in Symptoms . Powertrain On Board Diagnostic (OBD) System Check is an organized approach to identifying a problem created by an electronic engine control system malfunction.
The Powertrain Control Module (PCM) controls the malfunction indicator lamp (MIL) by providing a ground path through the MIL control circuit to turn ON the MIL. When the ignition is turned ON, the MIL will remain on until the engine is running, if no diagnostic trouble codes (DTC) are stored. If the MIL is illuminated, then the engine stalls, the MIL will remain illuminated so long as the ignition is ON.
Diagnostic Aids
Inspect for the following conditions:
Many situations may lead to an intermittent condition. Perform each inspection or test as directed.
Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
| • | Loose terminal connection |
| - | Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| - | Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| • | Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
| • | Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.
Malfunction Indicator Lamp (MIL) On Steady
The numbers below refer to the step numbers on the diagnostic table:
Step | Action | Values | Yes | No |
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 | With a scan tool observe the DTCs. Are any DTCs set? | -- | Go to applicable DTCs | |
3 |
Is the MIL ON?. | -- | ||
4 |
Does the MIL turn ON and OFF when commanded? | -- | Go to Diagnostic Aids | |
Test the MIL Control Circuit for a short to ground. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | ||
6 | Test the MIL Control Circuit for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
7 |
Does the MIL turn off when commanded? | -- |
