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 malfunction of the class 2 serial data circuit 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 on the class 2 serial data circuit that causes a short to voltage or ground.

The serial data communication circuit on this vehicle is a ring configuration. The ring may be conveniently split by disconnecting the powertrain control module (PCM) and sensing and diagnostic module (SDM) to aid in isolating the location of the concern.

TEST DESCRIPTION

Steps 1 - 9:

Steps 10 - 14:

Steps 15 - 20:

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 circuits:
- Body control module (BCM)
- Driver door module (DDM)
- Electronic brake control module (EBCM)
- Inflatable restraint sensing and diagnostic module (SDM)
- Instrument panel cluster (IPC)
- Instrument panel integration module (IPM)
- Memory seat module (MSM), w/A45
- Powertrain control module (PCM)
- Remote control door lock receiver (RCDLR)
- Theft deterrent control module (VTD)
4. The following DTCs may be retrieved with a history status. These DTCs 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 or U1255 with a current status. This indicates that the malfunction occurred when the ignition was on.
10. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
12. An open between the DLC and the class 2 serial data circuit will prevent the scan tool from communicating with any module. This condition will not set a DTC.
13. Splitting the class 2 serial data circuit will help isolate the location of the malfunction. If communication can be established, the malfunction is located in the wiring or one of the modules that is no longer connected to the DLC. If communication cannot be established, the malfunction is located in the wiring or one of the modules that is still connected to the DLC.