Initial Inspection

Circuit Description
The on-board diagnostic system check is the starting point for any driveability complaint diagnosis. Before using this procedure, perform a careful visual/physical check of the Powertrain Control Module (PCM) and engine grounds for cleanliness and tightness.

The on-board diagnostic system check is an organized approach to identifying a problem created by an electronic engine control system malfunction.

Diagnostic Aids
An intermittent may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside the insulation. Check for poor connections or a damaged harness. Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness.

Test Description
Number(s) below refer to the step number(s) in the Diagnostic Test:

1. The MIL ("Check Engine" lamp) should be "ON" steady with the Ignition "ON" engine "OFF". If not, isolate the malfunction in the MIL circuit.
2. Checks the Class 2 data circuit and ensures that the PCM is able to transmit serial data.
3. This test ensures that the PCM is capable of controlling the MIL and the MIL driver circuit is not shorted to ground.
4. If the engine will not start, the Cranks But Will Not Run test should be used to diagnose the condition.
7. A Scan Tool parameter which is not within the typical range may help to isolate the area which is causing the problem.
10. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.

Diagnostic Test
1. a. Ignition "ON", Engine "OFF".
b. Observe the Malfunction Indicator Lamp (MIL or "Check Engine" Lamp).
c. Is the MIL ("Check Engine" lamp) "ON" ?

[YES] Go to Step 2.
[NO] Go to No MIL test.

2. a. Ignition "OFF".
b. Install a Scan Tool.
c. Ignition "ON".
d. Attempt to display PCM Engine data with the Scan Tool.
e. Does the Scan Tool display PCM data?

[YES] Go to Step 3.
[NO] Go to Step 8.

3. a. Using the Scan Tool output tests function, select MIL Dash Lamp Control and command the MIL "OFF".
b. Observe the MIL.
c. Did the MIL turn "OFF" ?

[YES] Go to Step 4.
[NO] Go to MIL ("CHECK ENGINE" Lamp) On Steady.

4. a. Attempt to start the Engine.
b. Did the Engine start and continue to run?

[YES] Go to Step 5.
[NO] Go to Cranks But Will Not Run.

5. a. Select "Display DTCs" with the Scan Tool.
b. Are any DTCs stored?

[YES] Go to Step 6.
[NO] Go to Step 7.

6. Are two or more of the following DTCs stored?
- P0107
- P0108
- P0113
- P0118
- P0122
- P0123
- P1392
- P1406

[YES] Go to "Multiple PCM Information Sensor DTCs Set".
[NO] Go to applicable DTC table.

7. a. Compare PCM Data values displayed on the Scan Tool to the typical Engine scan data values.
b. Are the displayed values normal or close to the typical values?

[YES] Go to Typical Scan Data Values.
[NO] Refer to the indicated component system check.

8. a. Ignition "OFF", disconnect the PCM.
b. Ignition "ON", Engine "OFF".
c. Check the Class 2 data circuit for an open, short to ground, or short to voltage. Also, check the DLC Ignition feed circuit for an open or short to ground and the DLC ground circuits for an open.
d. If a problem is found, repair as necessary.
e. Was a problem found?

[YES] Go to Step 2.
[NO] Go to Step 9.

9. a. Attempt to reprogram the PCM.
b. Attempt to display PCM data with the Scan Tool.
c. Does the Scan Tool display PCM Engine data?

[YES] Go to Step 2.
[NO] Go to Step 10.

10. a. Replace the PCM.

IMPORTANT: The replacement PCM must be programmed.

b. Is the action complete?

[YES] Go to Step 2.