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 DLC allows communication with the modules for diagnostic purposes.

DIAGNOSTIC AIDS
The engine will not start when there is a total malfunction of the class 2 serial data circuit while the engine is not running.

TEST DESCRIPTION

Steps 1-10:

Steps 11-18:

Steps 19-26:

Steps 27-32:

The number(s) below refer to the step number(s) 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.
3. The DTC U1300, U1301, and U1305 may be retrieved with a history status. These DTCs are not the cause of the present condition.
4. A State of Health DTC with a history status may be present along with a U1000 or a U1255 with a current status. This indicates that the malfunction occurred when the ignition was on.
5. The Head Up Display (HUD), the Memory Seat Module (MSM), and the Remote Control Door Lock Receiver (RCDLR) are not monitored by other modules. When one of these modules is not communicating, diagnose the malfunction using the specified procedure.
6. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
8. An open in the class 2 serial data circuit between the DLC and connector C201 (w/o UV6) or splice 8202 (w/UV6) will prevent the scan tool from communicating with any module. This condition will not set a DTC.
9. The class 2 serial data circuit is shorted to voltage or to ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When you test the wiring for a short, make sure there is not a module connected to the wire being tested.
10. If communication can be established, the malfunction is in the Rear Integration Module (RIM), the Remote Playback Device - CD Changer, if equipped with U1S, the Vehicle Interface Unit (VIU) if equipped with EU1, the Sensing And Diagnostic Module (SDM), or the wiring between these devices
12. If communication can be established, the malfunction is in the Remote Control Door Lock Receiver (RCDLR), or the wiring between the RCDLR and the RIM.
14. If communication can be established, the malfunction is in the Electronic Brake Control Module (EBCM), the Memory Seat Module (MSM), if equipped with A45; or the wiring between these devices and the RCDLR. If communication cannot be established, the malfunction is in the Powertrain Control Module (PCM), or the wiring between the PCM and the EBCM.
17. If communication can be established, the malfunction is in the Driver Door Module (DDM), the Theft Deterrent Control Module, or the wiring between the PCM and the flex wiring harness.
18. If communication cannot be established, the malfunction is in the wiring between the theft deterrent control module and connector C215.
20. If communication can be established, the malfunction is in the HVAC Control Module, if equipped with C67: the Radio; the Instrument Panel Cluster (IPC): or the flex wiring harness. When the malfunction is in the flex wiring harness, the flex wiring harness must be replaced. If communication cannot be established, the malfunction is in the Dash Integration Module (DIM); the Head Up Display (HUD), if equipped with UV6; the Instrument Panel Integration Module (IPM), if equipped with CJ2; or the wiring connected to the DLC at terminal 2.
24. Since the short is not in the wiring harness the malfunction is due to one of the modules.
28. If there are no current DTCs that begin with a U, the communication malfunction has been repaired.
29. The communication malfunction may have prevented diagnosis of the customer complaint.

"For a description of the RPO Code(s) shown in this article or any of the images therein, refer to the RPO Code List found at Vehicle/Application ID". RPO Codes