Circuit Description
Powertrain On Board Diagnostic (OBD) 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. Refe to Visual/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. 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.
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 Powertrain On Board Diagnostic (OBD) System Check first, when the following conditions are present:
| • | 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. Refer to Wiring Repairs .
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 Intermittents and Poor Connections Diagnosis , and Connector Repairs Wiring Systems. |
| • | 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. Refer to Wiring Repairs in Wiring Systems. |
| • | 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:
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A no MIL condition accompanied by a no start condition suggests a faulty PCM ignition feed or battery feed circuit.
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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.
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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. Refer to PCM Replacement/Programming.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain OBD System Check performed? | -- | ||
Attempt to start the engine. Does the engine start? | -- | |||
3 | Test the fuse for the instrument cluster ignition feed circuit. Is the fuse OK? | -- | ||
4 |
Is the J 35616-200 test light on? | -- | ||
5 |
Is the MIL on? | -- | ||
6 | Test the PCM ignition feed and battery feed fuses. Are both of the fuses OK? | -- | ||
7 |
Is the J 35616-200 test light on? | -- | ||
8 | Probe the battery feed circuit at the PCM harness connector with a J 35616-200 test light to ground. Is the J 35616-200 test light on? | -- | ||
Was a problem found? | -- | |||
10 |
Was a problem found? | -- | ||
11 |
Was a problem found? | -- | ||
12 | Repair open in the ignition feed circuit to the instrument cluster. Refer to Wiring Repairs . Is the action complete? | -- | -- | |
13 | Locate and repair open in PCM battery feed circuit or PCM ignition feed circuit as necessary. Refer to Wiring Repairs . Is the action complete? | -- | -- | |
14 | Locate and repair short to ground in PCM ignition feed circuit or PCM battery feed circuit as necessary. Refer to Wiring Repairs . Is the action complete? | -- | -- | |
15 | Locate and repair short to ground in the instrument cluster ignition feed circuit. Refer to Wiring Repairs . Is the action complete? | -- | -- | |
Replace the PCM. Important: : Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
17 |
Was a problem found? | -- | Go to Instrument Panel in Electrical Diagnosis . |
