Transfer Case Encoder Motor

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Transfer Case Encoder Motor

Courtesy of GENERAL MOTORS CORP.

The transfer case encoder motor consists of a permanent magnet (PM) DC motor and gear reduction assembly. It is located on the left side, drivers side, of the transfer case. When activated, it turns the sector shaft of the transfer case clockwise or counter clockwise to shift the transfer case. The encoder motor is controlled by the transfer case shift control module. This circuit consists of a driver on both the motor control A and motor control B circuits. The encoder motor is bi-directional, to allow the motor to shift the transfer case from 2HI or 4HI to NEUTRAL and 4LO positions. The transfer case encoder motor can be fully driven clockwise or counterclockwise using a scan tool. You may also monitor motor control A and B circuits using a scan tool.

The encoder motor also has a built in encoder. This device is a linear encoder for 2003. The TCCM sends a 5 volt reference signal to the encoder. The TCCM reads the voltage back based on the exact position of the sector shaft of the transfer case. The TCCM knows if a shift has been completed and if the shift is somewhere in between.

The encoder motor on the NVG 263 does not have an internal brake like the NVG 246. The encoder motor is not serviceable and must be replaced as an assembly.