Mikes64

Can I piggyback these two at my fuse box safely and should they be fused?

ls1nova71

iTrader: (4)

I dont think you would want 12v on the TCC wire at all times, that could potentially keep power going to the converter and drain the battery.

Mikes64

I went back to the Lt1swap site, it does say 12v all the time, but I do agree with you, guess it should be on a ignition circuit?

LS1 TJ

It's been awhile since I've thought about this but the TCC/brake light switch should "open" when the brakes applied. Don't want it to be constant 12 volt because as said above it would drain you battery. Does your LS harness have one wire to the switch? Just one to open when the brakes are applied or two wires, one for power and then one going back to the ECM. I believe my harness from Howell had two wires. Can't hook it up wrong because all it has to is open the circuit releasing the lock up torque converter. My concern would be does the ECM really want 12 volt signal when most I/O of the ECM is 5 volt or less. I'm no expert on LS wiring that's why I buy the harness for well regarded suppliers.

ls1nova71

iTrader: (4)

This is what LT1Swap.com says, Pin 33 - Purple - TCC Brake Switch - This wire tells the PCM when you hit the brakes. It needs 12v+ all the time, and the brake switch should "open" this circuit when you hit the brakes. But what he is saying is that the pin33 needs power when the brakes are not applied which is kind of backwards from what people think, so he says it needs power all the time, but didn't mean constant battery power even when the car is off. It is somewhat confusing though.

There is another wire on DBW applications that needs power when the brakes are applied, it goes to the TAC module, that one you can tap directly off the brake switch that has constant power with no problem.

Mikes64

Thanks LS1 TJ and Eric, I should have mentioned in the beginning that I am not running a cruise control at this time but want this in place if needed, still learning here. Is this switch just for cruise control? Eric, the link to LT1 is what I was referring to, after reading again last night it made more sense. As far as the other wire for the DBW wire to the tach module, looks like I’ve missed that one. Can I find the info on this in the LT1 site?

ls1nova71

iTrader: (4)

The wire going to the PCM is for the torque converter lock up. The one going to the TAC is for cruise control, so if you dont plan on having cruise, you can omit that one.

john morse

My E-38 ECM wants 12 volts when brake is applied for converter control. As I have no lock up converter, I doubt that this circuit is even needed. 12 volts constant does not sound right to me but there are many variables across ECM,s, Powertrain components, etc
MY PSI Aftermarket harness stated "connect TCC wire to side of brake switch that gets 12 volts with brakes on only." LSX 6.2 Vortec with drive by wire is my application.
Though most of the sensors on 58X motors want a 5 volt reference, some want 12 volt signals. several ECM pins want 12 volt references...ie 12 volts constant, 12 volts with key on, 12 volts with brake applied, etc. Coils and injectors get 12 volts w/ key on and grounds are controlled by ECM - Research seems to provide the best answer for me. Lots of it.