For 1990-2009 cars

Refer to Engine Controls Schematics

#### Power and Ground

Engine Controls Components
MIL and DLC
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Cell 14: G105 and G106 (1 of 2)
Cell 14: SP254 and SP261
Cell 10: Ignition Switch, IGN Fuse, and ST Fuse
Cell 10: Ignition Switch, IGN Fuse, and ST Fuse
Cell 10: Alt-S, AM2, Dome, EFI, Hazard, Horn, and Main Fuses
and

#### MIL and DLC

Engine Controls Components
Main Power Feed
Power and Ground
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Cell 10: Gauge Fuse
Cell 10: ABS, Alt, AMI, Def, D/L, ECU-B, HTR, ODB, Power, and Stop Fuses
Cell 14: G106 (2 of 2)
Cell 14: G106 (2 of 2)
Cell 14: G105 and G106 (1 of 2)
Cell 14: G204 and SP256
Cell 81: ABS, Oil Pressure, MIL, O/D OFF, and Cruise Indicators
Cell 50: OBD II Connector
.

### Description

The Powertrain OBD System Check is an organized approach to identifying a problem created by an electronic engine control system malfunction. The Powertrain OBD System Check is the starting point for any driveability concern diagnosis, because it directs the service technician to the next logical step in diagnosing the concern. Understanding the table and using it correctly will reduce diagnostic time and prevent the replacement of good parts.

DO NOT perform this check if a driveability concern is not present.

### Diagnostic Aids

• | Inspect all the related wiring and connections for an intermittent malfunction, including the connections at the PCM. Inspect the electrical terminals for the following conditions:

- | Any damage

- | Any corrosion

- | Proper seating

• | Before proceeding to the applicable DTC table consider all of the items below:

- | Check for related service bulletins.

- | If multiple DTCs are stored, refer to the DTC tables using the following priority:

• | Any PCM error DTCs

• | Any system voltage DTCs

• | Any component level DTCs (sensors, switches, relays, output drivers, etc.)

• | Any system level DTCs (misfire, fuel trim, HO2S lean or rich, etc.)

- | First failures of Type B DTCs will store in Last Test Failed, but not in History. When the MIL is on and a DTC is displayed in History, a current fault is indicated.

- | Transmission DTCs are not located in this section. Refer to Automatic Transmission Diagnostic Information and Procedures.

- | If the scan tool is unable to record DTC information, then record the DTC information on paper.

• | For intermittents, refer to Symptoms .

### Test Description

The numbers below refer to the step numbers in the diagnostic table.

1. The OBD System Check should not be performed unless one of the concerns noted is present, failure to follow this procedure could lead to misdiagnosis of the system.

2. The MIL should be ON steady with the ignition ON and engine OFF.

3. Checking if the PCM and the scan tool can communicate.

4. This step checks if the vehicle starts.

5. Observes the DTC information. Ensures that items listed in Diagnostic Aids are considered before proceeding to the applicable DTC table.

1. Before proceeding to Symptoms or Components, check for related service bulletins. The diagnostic tables in this section are designed for use with a properly functioning scan tool. If a faulty scan tool is suspected connect it to another vehicle to verify operation. Serial data communications must be corrected before beginning any other diagnostic procedure. OBD II serial data may not transmit if system voltage is less than 9.0 volts or more than 16.0 volts. DO NOT clear DTCs unless directed by a diagnostic procedure. Clearing DTCs will also clear valuable Freeze Frame data.

#### Powertrain On-Board Diagnostic (OBD) System Check

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Important:

• | Check for service bulletins.

• | DO NOT turn OFF the ignition during this diagnostic unless instructed.

• | DO NOT clear the DTCs unless instructed.

Check for one or more of the following conditions:

• | The malfunction indicator lamp illuminates with the engine running.

• | Any customer concern of powertrain performance or driveability.

• | A suspected fault in a powertrain controlled component or system.

Were any of the above conditions found?

--

Go to Step 2

Go to Test Descriptions

2 |

1. Turn ON the ignition, with the engine OFF.
2. Observe the malfunction indicator lamp (MIL).

Is the MIL ON?

--

Go to Step 3

Go to Malfunction Indicator Lamp (MIL) Inoperative

3 |

1. Turn OFF the ignition.
2. Install a scan tool.
3. Turn ON the ignition, with the engine OFF.

Does the scan tool display any PCM data?

--

Go to Step 4

Go to Data Link Connector Diagnosis

4 | Does the engine start and run? | -- | Go to Step 5 | Go to Engine Cranks but Does Not Run
5 | Observe the DTC information. If DTCs are set, save the DTCs and the Freeze Frame information. Were any DTCs set? | -- | Go to Diagnostic Aids | Go to Step 6
6 | Is the MIL ON, with no DTCs set? | -- | Go to Malfunction Indicator Lamp (MIL) Always On | Go to Step 7
7 | Compare the scan tool data with the typical values shown in the Engine Scan Tool Data List. Are the displayed values normal or within typical ranges? | -- | Go to Symptoms | Go to Diagnostic Trouble Code (DTC) List .