My 85 El Camino will shift fine up to 3rd, but at slow acceleration and speed, it'll lockup and really lug the engine. I unplugged the wires from the trans, the problem went away, but now no lockup. I'm getting ready to rig a toggle switch to manually be able to control the lockup, but there's bound to be a way to fix this problem. My wiring diagram shows a TCC. Is this a black box that can be replaced? Is this my problem??? Thanks!!!

TCC (Trans Converter Clutch) lockup is controlled by the ECM and the brake pedal operated TCC switch. Depressing the brake pedal opens the power circuit to the TCC (pink/blk & purple wires) which disengages the TCC, regardless of what the ECM does, and the ECM grounds the tan/blk wire to engage the TCC, which happens only if the brake padal is not depressed. The light blue wire on the connector to the trans goes to the ECM & indicates that the trans is in 4th gear (not grounded in 4th).

Tim

Does this mean, then, that I have an ECM problem, trans. problem, or brake pedal problem?

When the trans shifts to 3rd, then TCC locks up, I apply brake, but the TCC doesn't disengage.

Thanks for the help!!

Sounds like 2 problems. The brake pedal TCC switch is not opening when the brake is depressed & the PROM in the ECM is engaging the TCC at too low a MPH.

Tim

I used a test bulb to verify that the brake pedal switch does, for certain, break the circuit.

What's strange is that it's an intermittent problem. After warmup, the TCC locks up as it should and will even work correctly even at slow speeds. Then it decides after a while to lock up in 3rd gear and lug the engine.
If it's a PROM fault, can it be changed out and are they available??
Could it also be a sticking TCC solenoid?? Would a trans. oil change help?

Thanks again, Tim!!

If you suspect a sticking TCC solenoid, I'd cut the TCC ground that goes to the ECM & connect it to a switch that is grounded. Manually control the TCC & if it sticks, then you will eliminate the ECM from the picture.

Tim