Scan Tool Does Not Communicate With Class 2 Device

SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE

CIRCUIT DESCRIPTION
Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a scan tool to the data link connector (DLC) allows communication with the modules for diagnostic purposes.

DIAGNOSTIC AIDS
The engine will not start when there is a total loss of class 2 serial data communication while the ignition is OFF. The following conditions will cause a total loss of class 2 serial data communication:
- A class 2 serial data circuit shorted to ground
- A class 2 serial data circuit shorted to voltage
- An internal condition within a module or connector on the class 2 serial data circuit, that causes a short to voltage or ground to the class 2 serial data circuit

TEST DESCRIPTION

Steps 1 - 11:

Steps 12 - 21:

Steps 22 - 24:

The numbers below refer to the step numbers on the diagnostic table.
2. A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. The following modules communicate on class 2 serial data bus:
- The audio amplifier (AMP)
- The CD changer (CDX)
- The dash integration module (DIM)
- The digital radio receiver (DRR)
- The digital video disc (DVD) player
- The driver door module (DDM)
- The driver door switch assembly (DDSA)
- The electronic brake control module (EBCM)
- The electronic suspension control (ESC) module
- The engine control module (ECM) communicates functionally on class 2 and high speed GMLAN, but with scan tool it communicates via high speed GMLAN only
- The front passenger door module (FPDM)
- The HVAC control module
- The inflatable restraint sensing and diagnostic module (SDM)
- The instrument panel cluster (IPC)
- The left rear door module (LRDM)
- The memory seat module (MSM) w/A45
- The radio
- The radio antenna module
- The rear integration module (RIM)
- The rear seat module (RSM)
- The right rear door module (RRDM)
- The theft deterrent control module
- The TV antenna module
- The vehicle communication interface module (VCIM)
3. The following DTCs may be retrieved with a history status, but are not the cause of the present condition:
- U1300
- U1301
- U1305
6. A state of health DTC with a history status may be present along with a U1000 code having a current status. This indicates that the malfunction occurred when the ignition was ON.
7. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
10. This step takes out from the class 2 bus the modules connected to splice pack SP304, excepting SDM and RIM.
11. This step takes out from the class 2 bus the modules connected to splice pack SP300, excepting IPC.
13. This test isolates the class 2 serial data circuit between DLC and DIM.
18. This test localizes the class 2 serial data circuit of the suspected bus that is shorted.
22. If there are no current DTCs that begin with a U, the communication malfunction has been repaired.
23. The communication malfunction may have prevented diagnosis of the customer complaint.