The automatic transfer case (ATC) accessory switch consists of 4 modes. The transfer case shift control module supplies 5 volts to the ATC accessory switch mode buttons. A signal switch low circuit completes the circuit back to the transfer case shift control module. The voltage on the switch signal circuit will vary depending on which button is pressed. When selected, each mode will complete a circuit through their own specific resistor. The transfer case shift control module continuously monitors the switch signal circuit to determine whether the Neutral, 2HI, 4HI, or 4LO mode was selected by the vehicle operator.

A low battery condition or charging system that is faulty could set this DTC. Refer to Battery Inspection/Test and Charging System Test .

Schematic Reference

Transfer Case Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Transfer Case Description and Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, engine OFF, with a scan tool command each mode function switch ON one at a time, on the instrument panel accessory switch. Each mode button indicator light should illuminate.
2. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records Data.

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Ignition OFF, disconnect the accessory switch electrical connector.
2. Verify that a test lamp illuminates between B+ and terminal H of the accessory switch electrical connector.

⇒	If the test lamp does not illuminate, test the ground circuit for an open/high resistance.

3. Ignition ON, engine OFF, verify that a test lamp illuminates between terminal A and ground.

⇒	If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance.

4. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal M and ground.

⇒	If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the transfer case shift control module.

⇒	If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the transfer case shift control module.

5. Ignition OFF, install a 3 A fused jumper wire between the switch signal low circuit terminal N and the 5-volt reference circuit terminal M at the accessory switch.
6. Disconnect the transfer case shift control module connector C1.
7. Ignition ON, verify 4.8-5.2 volts is present at connector C1 terminal 14.

⇒	If less than the specified range, test the switch signal low circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the transfer case shift control module.

⇒	If greater than the specified range, test the switch signal low circuit for a short to voltage. If the circuit tests normal, replace the transfer case shift control module.

8. If all circuit tests normal, replace the accessory switch.

Important: You must perform the Circuit/System Testing before proceeding to Component Testing.

1. Disconnect the accessory switch electrical connector.
2. Connect a DMM between the switch signal low circuit and the 5-volt reference circuit at the accessory switch.
3. Measure the resistance while pressing and holding each of the mode buttons. The resistance values should be within the specified ranges:

•	4HI: 656.2-669.4 ohms

•	2HI: 1.50-1.53 K ohms

•	Neutral: 1.010-1.031 K ohms

•	4LO: 2.32-2.36 K ohms

•	Normal: 9.00-9.18 K ohms

⇒	If the resistance values are not within the specified range, replace the accessory switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.