TCC Question

Only if it was an electrical problem like the wires loose or burnt or shorted. Mechanical problem with the TC clutch itself will not usually do it.

the CE light will come on any time the ECM sees an incorrect ratio for the proper circumstances

so ANY TCC problem that prevented a 1:1 in 3rd with TC locked, or whatever ratio the OD in the vehicle has with TC locked, will set it

GM has the infamous P-1870 which simply means 'transmission component slipping', it can be anything from a bad brake switch to an internal problem in any of 4 areas (forward pack, 3-4 pack, band, or TC {for the 4L60E})

Why would a brake switch flag a slipping trans code?

because power for the TCC on-off solenoid (pre-01) goes thru the NC contacts on the switch (GM trucks)

if the witch is bad (open at rest) the TCC cannot come on

it usually flags an additional code of the P-188X variety which signals an electrical problem in the TC solenoid circuit....BUT it will ALWAYS flag an

Ok, now it make sense, thanks Gary