Malfunction Indicator Lamp (MIL) Inoperative

Circuit Description

A Diagnostic System Check must be the starting point for any driveability complaint diagnosis. Before using this procedure, you should perform a careful visual/physical check of the PCM and engine grounds for being clean and tight. Refer to Visual/Physical Check in Symptoms. A Diagnostic System Check is an organized approach to identifying a problem created by an electronic engine control system malfunction. No MIL with the key ON, engine not running and DTC P0650 Malfunction Indicator Lamp (MIL) Control Circuit set suggests an open in the MIL driver circuit. Initial Inspection and Diagnostic Overview

MIL Operation

The Malfunction Indicator Lamp (MIL) is located on the instrument panel (CHECK ENGINE) or (SERVICE ENGINE SOON). The MIL performs the following functions:

^ It informs the driver that a problem has occurred and that the vehicle should be taken for service as soon as possible.
^ As a bulb check and system check, the MIL will illuminate with the ignition switch on and the engine not running. when the engine is started, the MIL will turn off. If the MIL remains on, the self-diagnostic system has detected a problem. If the problem goes away, the MIL will turn off in most cases, but a diagnostic trouble code will remain stored.
^ If the MIL is illuminated, then the engine stalls, the MIL will remain Illuminated so long as the ignition switch is on.
^ If the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition switch is cycled off, then on.

Perform A Diagnostic System Check first, when the following conditions are present: Initial Inspection and Diagnostic Overview

^ When the MIL does not turn on when the ignition switch is turned to the RUN position.
^ When the MIL remains on while the engine is running.
^ When you suspect a driveability problem.

Diagnostic Aids

Inspect for the following:
If the engine cranks but will not run, check for an open PCM ignition or battery feed or a poor PCM to engine ground.

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.

^ Poor terminal connection.
Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension. Refer to Diagrams.
^ Damaged harness.
Inspect the wiring harness for damage. If the harness appears to be OK, observe the sensor display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the sensor display may indicate the location of the fault.
^ Inspect the PCM and the engine grounds for clean and secure connections.

If the DTC is determined to be intermittent, reviewing the Fail Records can be useful in determining when the DTC was last set.

Test Description

The numbers below refer to the Step numbers on the Diagnostic Table:

2. A no MIL condition accompanied by a no start condition suggests a faulty PCM ignition feed or battery feed circuit.
9. Using a J 34142-B test light connected to battery positive voltage, probe each of the PCM ground terminals to ensure that a good ground is present. Refer to PCM Terminal End View for terminal locations of the PCM ground circuits. Connector Views
16. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.