Data Link Connector Diagnosis

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 II serial data line is used to communicate with other modules such as the Electronic Brake Control Module (EBCM) and the Body Function Controller (BFC).

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.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame Data and the Failure records on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. This information on the scan tool can be referred to later.
5. Check for proper voltage supply in the DLC.
7. Locate and repair any shorts that may have caused the fuse to open before replacement, if the no voltage conditions was due to an open fuse.
13. The replacement PCMs must be reprogrammed and the crankshaft position system variation procedure must be performed. Refer to the latest Techline information for PCM programming and Powertrain Control Module for the Crankshaft Position System Variation Procedure. Testing and Inspection
15. The scan tool, or associated cables could be malfunctioning. Refer to the scan tool manual for repair information.
16. If the serial data loss occurred after a good theft password has been received, the PCM will allow the vehicle to be started on following attempts. After making the necessary repairs to the vehicle the PCM must be reprogrammed and the password learn procedure and the crankshaft position system variation procedures must be completed to allow the theft system to operate properly, Refer to the Powertrain Control Module for the reprogramming procedures.