Circuit/System Description

A signal circuit is provided by the body control module (BCM) to the Tow/Haul switch. When tow/haul mode is pressed, the tow/haul switch input signal to the BCM is momentarily toggled to zero volts. The BCM is constantly sending the transmission control module (TCM) serial data messages with information regarding the status of the Tow/Haul switch. This signals the transmission control module (TCM) to change the shift points, the application of TCC, and transmission line pressure. The TCM sets this DTC when it detects a discrepancy in the structure of this message causing its integrity to be questioned.