Circuit/System Description
WARNING: This page is about a different car, the 2008 Isuzu i-370, 2008 Isuzu i-290, 2008 GMC Canyon, and 2008 Chevrolet Colorado. However, it is still accessible from the selected car via links, so may be relevant.
After the traction control switch (TCS) is pressed and released, the LED on the switch illuminates. The body control module (BCM) illuminates the LED by supplying adequate current to the high side of the LED. The BCM supplies a low current, 12-volt signal to the TCS requested indicator control circuit, when the LED is commanded OFF. The BCM monitors the feedback from this signal to detect opens or shorts to voltage in the LED control circuitry.