Scan Tool Does Not Communicate With Class 2 Device

CIRCUIT DESCRIPTION
Modules connected to the class 2 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. 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.

DIAGNOSTIC AIDS
^ When the class 2 circuit is shorted to ground, U1300 will be set. Refer to DTC U1300. U1301
^ When the class 2 circuit is shorted to battery positive voltage, U1301 will be set. Refer to DTC U1301. U1301

TEST DESCRIPTION

Steps 1-4:

Steps 5-12:

Steps 13-19:

Steps 20-25:

2. A partial malfunction in the class 2 circuit uses a different procedure from a total malfunction of the class 2 circuit. The following modules communicate on the class 2 circuit:
^ Electronic brake control module (EBCM)
^ Powertrain control module (PCM)
^ Radio (IRC)
^ Vehicle theft deterrent (VTD)
^ Vehicle immobilizer module (VIM)
^ Inflatable restraint Sensing And Diagnostic Module (SDM)
3. The following DTCs may be retrieved with a history status:
^ U1300
^ U1301
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 U1255 having a current status. This indicates that the malfunction occurred when the ignition was ON.
5. DLC terminals 2 and 5 provide the connection to the class 2 circuit and the signal ground circuit.
7. Poor continuity at 5207 and/or S153 would cause this condition but will not set a DTC.
8. An open in the class 2 circuit between the DLC and S207 will prevent the scan tool from communicating with any module. This condition will not set a DTC.
9. The class 2 circuit is shorted to battery positive voltage or ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When testing the wiring for a short, make sure there is not a module connected to the wire being tested. This test isolates the IRC class 2 circuit.
11. This test isolates the PCM class 2 circuit.
13. This test isolates the VTD/VIM class 2 circuit.
15. This test isolates the EBCM class 2 circuit.
17. This test isolates the SDM class 2 circuit.
25. If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.