Scan Tool Testing and Procedures

Circuit Description

The Data Link Connector (DLC) allows the scan tool to interface with the PCM. The DTC provides the power and ground circuits to enable the scan tool. The Class II serial data circuit to the DLC allows bi-directional communication between the PCM and the scan tool. If communication between the scan tool and the PCM cannot be established, the procedure in the DLC Diagnosis table should be used to diagnose the condition.

Diagnostic Aids

Check the following items:

^ For the PCM to establish communication with the scan tool, system voltage must be between 9.0 and 16.0 V. If system voltage is not within this range.
^ 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. 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. Refer to Diagrams.

Test Description

The number below refers to the step number on the Diagnostic Table:

11. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.