1993 CTS switch

[Matt C]

Just acquired a '93 K2500 Vin F from my father in law, had a few issues, ive resolved a few need some help on others. When I got it it wouldn't shift unless you revved it straight to the danger zone, check TPS couldn't get it set in spec, so I swapped with my old 6.2. Got it so it shifts nice through all 4 but I'm not getting T/C lockup. I'll have access to a scanner shortly, maybe brake switch? Other issue is the CTS for the cold idle/advance is stuck on, if it's plugged in it's on fast idle, unplugged it slows down. I'm not really wanting to spend $80-$120 for a new switch. Has anyone converted to a new style? All it really has to do is break contact at 100 degrees correct? Otherwise I'll just put it on a toggle like my '91 was. Thanks in advance

 

[dbrannon79]

I think on the cold idle temp sensor it just simply passes power through to the idle advance on the IP and the high idle solenoid, it doesn't run through anything that would stop the TCC from working. only thing that controls the TCC is the brake light switch, TPS, and crank signal. you should have a sensor on the oil pump drive that sends RPM signal to the TCM.

if there is a code present for the TPS since it was previously not adjusted correctly, that will prevent the TCC from activating. try to disco the batteries for about 5 minutes to clear out any remaining codes and then try it again. drive up to about 50-55 mph on a flat road. easiest way for me to tell if it's working is under a very light load doing 50-55 is to lightly step on the brake just enough to activate the tail lights and watch the RPM. you should see about a 200 RPM increase and when you let off the pedal the RPM will lower about the same amount.

if the trans and torque converter is factory and has had a life of towing and hauling, the TCC might be smoked to the point that you'll never feel it, the tcc lockup is the weakest link in the 4l80e

 

[Matt C]

Trans is a rebuild over 10 years ago, but only probably 5,000 miles on it, he basically parked it when it didn't shift. I figured out the tcc now that I got a scanner, if I lift up on the left side of the brake pedal with my foot, the status goes from off to on and it locks up, let go of the pedal it unlocks. Now I just gotta see if if adjustable or needs to be replaced

 

[dbrannon79]

There should be an adjustment under there. iirc the switch is separate from the brake light switch and will have a threaded shank with a button on the end.

 

[dbrannon79]

There may also be a spring on the pedal linkage that helps hold the pedal back when not pushing on it. that spring might be worn out too depending on how much it moves up when not pressing on it.