Data Link Communications System: Other Chevrolet TrailBlazer I

Conditions for Setting the DTCs

1. No valid messages are detected on the class 2 serial data circuit.
2. The voltage level detected on the class 2 serial data circuit is in one of the following conditions: High Low
3. The above conditions are met for approximately 3 seconds.

Action Taken When the DTCs Sets

The module uses default values for all parameters received on the class 2 serial data circuit.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.

Data Link Connector (DLC)

The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard, and is required to provide the following

1. Scan tool power battery positive voltage at terminal 16.
2. Scan tool power ground at terminal 4.
3. Class 2 serial data at terminal 2.
4. Common signal ground at terminal 5.

Class 2 Serial Data Line

The class 2 serial data line on this vehicle is a star configuration. The PCM has an additional class 2 serial data circuit to BCM or to theft deterrent control module, if equipped. If one of the class 2 serial data circuits to the PCM opens, communication will not be interrupted. The following modules communicate on the class 2 serial data line

1. The audio amplifier
2. The body control module (BCM)
3. The driver door module (DDM)
4. The electronic brake control module (EBCM)
5. The front passenger door control module (FPDM)
6. The HVAC control module
7. The inflatable restraint sensing and diagnostic module (SDM)
8. The instrument panel cluster (IPC)
9. The liftgate control module (LGM)
10. The memory seat module-driver, w/power seat
11. The memory seat module-passenger, w/power seat
12. The powertrain control module (PCM)
13. The radio
14. The RSA/HVAC control module-rear auxiliary
15. The theft deterrent control module, for export
16. The transfer case shift control module, w/4WD
17. The vehicle communication interface module (VCIM), w/UE1

The class 2 serial data line allows a scan tool to communicate with these modules for testing purposes, checking for DTCs, and to activate/enable/disable functions. These class 2 serial data circuits are bussed together via two splice packs and a data link connector (DLC)

1. SP205 - Located behind the I/P near the headlamp switch connector.
2. SP306 - Located in the body harness near the rear of the right rear seat under the carpet.
3. DLC - Connects the scan tool to the class 2 serial data circuits.

Refer to DATA LINK COMMUNICATIONS COMPONENT VIEWS .