Transfer Case Diagnostic System Check
WARNING: This page is about a different car, the 2001 GMC Safari and 2001 Chevrolet Astro. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Presence of DTCs which begin with "U" indicate some other module on class 2 serial data line is not communicating.
NOTE:
Vehicle speed is provided to transfer case shift control module via Class 2 and can effect setting of DTC C0300. Perform diagnostics for powertrain DTCs P0502 and P0503 first.
NOTE:
Perform diagnostics for DTC C0300 and C0305 first before addressing other DTCs. DTC C0300 and C0305 can be responsible for setting other DTCs.
- Connect scan tool to Data Link Connector (DLC). DLC is located under left side of instrument panel. If scan tool powers up, go to next step. If scan tool does not power up, go to TEST E: SCAN TOOL DOES NOT POWER UP under SYSTEM TESTS.
- Turn ignition switch to RUN position. Attempt to establish communication with Transfer Case Shift Control Module (TCSCM) on class 2 serial data circuit. If scan tool communicates with BCM, go to next step. If scan tool does not communicate with BCM, go to TEST D: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SYSTEM TESTS.
- Using scan tool, select DISPLAY DTCS function. Retrieve and record any TCSCM DTCs and their status. If scan tool displays any DTCs, go to next step. If scan tool does not display any DTCs, repair system by symptom. See appropriate article in AUTOMATIC TRANSMISSIONS.
- If scan tool does not display any DTCs which begin with a "U", go to next step. If scan tool displays any DTCs which begin with a "U", go to TEST D: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SYSTEM TESTS.
- If scan tool displays DTC P0502 or P0503, C0300 or C0305, perform appropriate test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .