ATC and the TC Dash Switch

Automatic Traction Control (ATC) is tied to the Anti-lock Brake System ABS (ABS). Nearly all tractors built after August of 2019 have ATC, due to FMVSS 136. Currently it is optional on trucks.

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What does the TC switch do?

Press and release the switch, and ATC goes into “mud-and-snow” mode, which allows a little more wheel spin than otherwise permitted.

Another function of ATC is engine de-rate, and this switch prohibits the throttle from backing off a little longer. The combination assists the vehicle when it is bogging down in mud or snow conditions, which could lead to becoming completely stuck. 

A dash light advises the driver that this feature is engaged. The system stays in this mode until either A) the switch is pressed again, B) the truck reaches 25 mph, or C) the key is turned off.  

The perception is this switch turns off the ABS/ATC, but that is not true. On vehicles with multiplexing architecture the speed at which this feature automatically disengages is programmable within a range (upper limit is around 35 mph). 

Note that while using the TC switch is helpful, this feature in general, is not a replacement for locking axles. ATC is for occasional adverse conditions on maintained roads, not aggressive off-road action.