For 1990-2009 cars
Data Link Communications Components
Data Link Connector Schematics
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The provision for communicating with the control module is the Data Link Connector (DLC). It is usually located under the instrument panel. The DLC is used to connect to a scan tool. Some common uses of the scan tool are listed below:

• | Identifying stored Diagnostic Trouble Codes (DTCs).

• | Clearing DTCs.

• | Performing output control tests.

• | Reading serial data.

Battery power and ground is supplied for the scan tool through the DLC. The Class 2 serial data circuit to the DLC allows the PCM to communicate with the scan tool. A Class 2 serial data line is used to communicate with other modules such as the Electronic Brake Control Module (EBCM) and the Body Control Module (BCM).

### Diagnostic Aids

Some scan tools may require an external power supply. Make sure your scan tool is using the correct power feed.

Ensure that the correct application (model year, carline, VIN code) has been selected on the scan tool. If communication still cannot be established, try the scan tool on another vehicle to ensure that the scan tool, or cables are not the cause of the condition.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.

Any circuitry, that is suspected as causing an intermittent complaint, should be thoroughly checked for the following conditions:

• | Backed out terminals.

• | Improper mating of terminals.

• | Broken locks.

• | Improperly formed or damaged terminals.

• | Poor terminals to wiring connection.

• | Physical damaged to the wiring harness.

• | Corrosion.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Important: A short to ground will cause an open fuse(s). Before performing this diagnostic procedure, inspect the fuse(s) for an open.
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check 2.4L or Powertrain On Board Diagnostic (OBD) System Check 3.4L
2 |

1. Turn ON the ignition switch leaving 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 | Install a scan tool. Does the scan tool power up? | -- | Go to Step 4 | Go to Step 6
4 | Attempt to communicate with the following control modules with the scan tool:

• | Body Control Module (BCM)

• | Electronic Brake Control Module (EBCM)

Does the scan tool communicate with the control modules?

--

Go to Step 6

Go to Step 5

5 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM electrical connectors.
3. Turn ON the ignition switch leaving the engine OFF.
4. Attempt to communicate with the following control modules with the scan tool:
5. Body Control Module (BCM)
6. Electronic Brake Control Module (EBCM)

Does the scan tool communicate with the control modules?

--

Go to Diagnostic System Check - Data Link Communications

Go to Step 6

6 |

1. Check for the following condition(s) in the Class 2 Serial data line from the splice to the PCM:

• | Poor electrical connection

• | Open in the circuit

2. Repair the condition(s) as necessary.

Was a repair necessary?

--

Go to Diagnostic System Check - Data Link Communications

Go to Step 7

7 |

1. Idle the engine until the normal operating temperature is reached.
2. Check to see if any DTCs are set.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Applicable DTC Table

Go to Diagnostic System Check - Data Link Communications