Vehicle On-Board & Scan Tool Diagnostics

Data Link Connector Diagnosis

Circuit Description

Caution: Refer to Defective Scan Tool Notice Defective Scan Tool Notice in Cautions and Notices.

The provision for communicating with the engine control module (ECM) is the data link connector (DLC). It is located under the instrument panel. The DLC is used to connect the scan tool. Battery power and ground is supplied to the scan tool through the DLC. The serial data circuit to the DLC allows the ECM and the transmission control module to communicate with the scan tool. A universal asynchronous receiver transmitter (UART) serial data line is used to communicate with the supplemental inflatable restraint (SIR) system. Other serial data lines communicate with the electronic brake control module (EBCM) and the speed sensitive power steering (SSPS) module.

Diagnostic Aids

Ensure that the correct application, model line, car year, etc., 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 broken wire inside the insulation.

Any circuitry that is suspected of causing an intermittent complaint should be thoroughly inspected for the following conditions:

* Backed-out terminals
* Improper mating of terminals
* Broken locks
* Improperly formed or damaged terminals
* Poor terminal-to-wiring connection
* Physical damage to the wiring harness
* Corrosion