For 1990-2009 cars

### Circuit Description

The accessory switch circuit consists of 4 modes. The transfer case shift control module supplies 5 volts to the switch through the switch signal circuit. The current travels through the resistor of the currently active mode. The current on the switch signal circuit is monitored by the transfer case shift control module. The voltage on the switch signal circuit will vary depending on which mode button is pressed by the driver.

The transfer case shift control module constantly monitors the switch signal circuit to determine the condition of the accessory switch circuit.

When each of the modes are selected they 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 driver.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step tests the accessory switch for proper resistance values in all mode switch states.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Transfer Case Control Schematics Connector End View Reference: Transfer Case Control Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. With the switch disconnected, connect a DMM between the accessory switch signal circuit and the 5 volt reference circuit at the switch.
2. Measure the resistance through the accessory switch while pressing and holding each of the mode buttons and comparing values.

Does the DMM indicate all resistance values within the specified ranges?

4 HI: 656.2-669.4 ohms

2 HI: 1.50-1.53 K ohms

Neutral: 1.010-1.031 K ohms

4 LO: 2.32-2.36 K ohms

Normal: 9.00-9.18 K ohms

Go to Step 4

Go to Step 3

3 | Replace the accessory switch. Refer to Accessory Switch Replacement . Did you complete the repair? | -- | Go to Step 5 | --
4 | Replace the transfer case shift control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the repair? | -- | Go to Step 5 | --
5 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle to determine if the symptom has been corrected.

Is the symptom still present?

--

Go to Step 2

System OK