P01 manual calibration.....is the brake switch input necessary?

[cobra30689]

I have a 4.8/NV3500 swapped into a Jeep YJ. Homemade harness, and reflashed the PCM with a manual calibration from GM SPS. As of right now the brake light switch wire is not connected, so my Tech 2 reports that the brakes are applied all the time. I also have no VSS, so I understand that DFCO will not function (as well as all the other idiosyncrasies involved with not having one, and have made adjustments for that). Are there any other tune strategies that depend on brake switch input? I can't seem to find anything, either here or in GM factory documentation.

[blindsquirrel]

Brake Torque Management, for one thing. Without a tune file to look at nobody knows if you've disabled that yet.

Would it not be easier to just wire up the brake switch? Is there some supposed benefit to not having it connected that outweighs all the unknowns you get by leaving it out?

[cobra30689]

I've attached my tune file for your review. My Jeep has a Ford-style, normally open brake switch. No provisions for changing to a GM-style switch with the additional set of normally closed contacts for TCC control (which does not apply as I have a manual) and the brake lamp circuit to the PCM. I'd have to set up a relay to perform that function. As per GM documentation the trucks have the same switch regardless of transmission, as the brake lamp circuit is also used for cruise control cancel....which I also don't have.

[blindsquirrel]

So tee into the existing switch, use that to control a relay wired to mimic the signal the GM brake switch provides. Done all the time on swaps to solve your exact problem.