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ATC System Check

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 1998 GMC Yukon, 1998 GMC Suburban, 1998 GMC Pickup, 1998 GMC Cab & Chassis, and 1998 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.

Before proceeding with transfer case electronic controls diagnosis, perform the following test procedure. This procedure checks Class II communication between Automatic Transfer Case (ATC) control module and scan tool, checks static system operation, and also checks park/neutral switch input operation.

  1. Connect scan tool to DLC. Turn ignition switch to run position (engine off). Use scan tool to communicate with Class II data bus, ATC control module, Electronic Brake Control Module (EBCM) and Vehicle Control Module (VCM) or Powertrain Control Module (PCM). If communication link is okay, go to next step. If communication is not okay, diagnosis Data Link Connector (DLC) malfunction. See DLC DIAGNOSIS OR NO SCAN TOOL DATA article in appropriate SELF-DIAGNOSTICS article:
  2. Using scan tool, check for any DTCs present in Anti-Lock Brake System (ABS). If any DTCs are present, see ANTI-LOCK BRAKE SYSTEM article in the BRAKES section. If no DTCs are present, go to next step.
  3. Using scan tool, check for any DTCs in VCM or PCM, as equipped. If any DTCs are present, see appropriate SELF-DIAGNOSTICS article in the ENGINE PERFORMANCE section. If no DTCs are present, go to next step.
  4. Using scan tool, check for any DTCs in ATC control module. If any DTCs are present, go to appropriate DTC test. See DIAGNOSTIC TROUBLE CODE (DTC) DEFINITIONS  table. If no DTCs are present, go to next step.
  5. With scan tool installed to DLC, set parking brake, shift transmission to "N" position, and start and run engine at idle. Read motor/encoder gear position on scan tool while shifting transfer case through all modes, allowing time for system to complete each shift request. If scan tool shows correct gear positions, go to next step. If scan tool does not show correct gear positions, see DTC C0327.
  6. With scan tool installed to DLC, set parking brake, shift transmission to "N" position, and start and run engine at idle. Read gear position on scan tool while shifting transmission from "N" to "P", then back to "N" position. If scan tool shows correct gear positions or requested gear position, go to next step. If scan tool does not show correct gear positions, see DTC C0357  under DTC TESTS or TRANSFER CASE WILL SHIFT RANGES WHEN TRANSMISSION IS IN PARK  (NV 246) test under SYMPTOM TESTS for park/neutral position switch diagnosis.
  7. Road test vehicle, if necessary to identify customer complaint (shift from 2H to AUTO to 4WD). Using scan tool, check for DTCs. If any DTCs are present, see appropriate DTC test. If multiple DTCs are present, always start diagnosis with last DTC displayed. One malfunction can trigger multiple DTCs. If no DTCs are present, system is functioning properly.
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