Scan Tool Does Not Communicate with Class 2 Device

Scan Tool Does Not Communicate with Class 2 Device

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview)provides an overview of each diagnostic category.



Diagnostic Fault Information






Circuit Description

The powertrain control module (PCM) is connected to the class 2 serial data circuit. The class 2 serial data circuit is used for diagnostic purposes only in this vehicle. Connecting a scan tool to the data link connector (DLC) allows communication with the PCM for diagnostic purposes. DTCs may be set due to this symptom and during this diagnostic procedure. Complete the diagnostic procedure in order to ensure all the DTCs are diagnosed and cleared from memory.


Reference Information
Schematic Reference

Data Communication Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Body Control System Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Refer to Control Module References (Programming and Relearning) for scan tool information.


Circuit/System Testing

1. Test for less than 1.0 ohm of resistance between the DLC ground circuit terminal 5 and ground.

• If greater than 1.0 ohm, test the ground circuit for open/high resistance.

2. Ignition OFF, disconnect the X1 harness connector at the PCM.
3. Test for less then 5 ohms between the class 2 serial data circuit terminal 16 and gronud.

• If greater then the specified range, test the serial data circuit for a short to open/high resistance.

4. Ignition ON, test for less then 1 volt between the serial data circuit terminal 16 and ground.

• If greater then the specified range, test the serial data circuit for a short to voltage.

5. If all circuits test normal, replace the PCM.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the repair.

* Control Module References (Programming and Relearning)for module replacement, setup, and programming
* GMLAN Wiring Repairs (Component Tests and General Diagnostics)