Scan Tool Does Not Communicate With Class 2 Device

SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE

CIRCUIT DESCRIPTION
Each module connected to the class 2 serial data circuit monitors 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
- 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.
- The body control module (BCM) must be connected to the class 2 serial data circuit for any other module to communicate with the scan tool. The BCM detects that the ignition is ON and sends the appropriate power mode message to wake up the other modules.
- When the class 2 serial data circuit is shorted to ground or voltage, the following DTCs may set:
- U1300
- U1301
- U1305

TEST DESCRIPTION

Steps 1-10:

Steps 11-17:

Steps 18-20:

The numbers below refer to the step numbers on the diagnostic table.
2. A partial loss of communication in the class 2 serial data circuit uses a different procedure than a total loss of communication of the class 2 serial data circuit.
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. Use the DTC U1000 or U1255 diagnostic procedure if there is communication with some but not all modules, and no DTCs are set.
10. Normal class 2 serial data communication cannot take place until the BCM sends the appropriate power mode message. If the BCM does not send a wake-up message, other modules on the class 2 serial data circuit may not communicate.
14. The circuit and module that you jumpered to the DLC class 2 serial data circuit when you lost communication with the BCM is suspect.
19. The communication concern may have prevented diagnosis of the customer complaint.