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 - 19:

Steps 20 - 22:

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 the class 2 serial data circuit:
- The body control module (BCM)
- The driver information center (DIC), w/Trip
- The electronic brake control module (EBCM)
- The inflatable restraint sensing and diagnostic module (SDM)
- The instrument panel cluster (IPC)
- The memory seat module (MSM) - driver, w/D44
- The powertrain control module (PCM)
- The radio
- The transfer case shift control module (TCSCM), w/NP8
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 or U1255 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. A poor connection at DLC terminal of the splice pack SP201 would cause this condition but will not set a DTC.
11. An open in the class 2 serial data circuit between the DLC and splice pack SP201 will prevent the scan tool from communicating with any module. This condition will not set a DTC.
12. The class 2 serial data circuit is shorted to voltage or ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When testing the wire for a short, make sure there is not a module connected to the wire being tested. This test isolates the BCM class 2 serial data circuits.
13. There is a redundant class 2 serial data circuit between BCM and PCM.
16. The BCM detects that the ignition is ON and sends the appropriate power mode message to the other modules. Therefore, the BCM must remain connected to the DLC for any other module to communicate with the scan tool. This test isolates the rest of the splice pack SP201 serial data circuits.
20. If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
21. The communication malfunction may have prevented diagnosis of the customer complaint.