Circuit Description

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The transfer case shift control switch circuit consists of 3 normally open switches. The transfer case shift control module supplies a regulated 8 volts DC to the switch through the 8 volt-reference circuit. The current travels through a 9.09 K ohms resistor located inside the switch. Then switch returns current to the transfer case shift control module through the 4WD switch signal circuit.

The transfer case shift control module constantly monitors this signal voltage to determine the condition of the shift control switch circuit. The transfer case shift control module will set this DTC if any of the following conditions exist:

None of the buttons are pressed, and the transfer case shift control module detects a voltage level outside the possible range (approximately -0.5 to +1.0 volts) for more than 5 minutes
A button is held down, or a button is stuck in the down position for a period more than 5 minutes

Each switch will complete a circuit through that switch's own specific resistor, when depressed. The transfer case shift control module continuously monitors the switch input to determine if the following button selections are made by the driver:

4HI
2HI
4LO
Neutral may be obtained if the following conditions are met:
The engine is running.
The automatic transmission is in neutral, or the clutch pedal is depressed on a manual transmission application
The vehicle speed is below 5 km/h (3 mph).
The transfer case is in the 2HI mode.

Once these conditions have been met, press and hold both the 2HI and 4LO buttons for 10 seconds in order to shift the transfer case into neutral. The red neutral indicator lamp will illuminate.