TCC GenIV lockup

[Smurfeh]

Alright, 2007 dbw Gen4 4L60e 84 K5 Blazer.

I think my Tq converter isn't locking up. Is it 12v when brake is applied or 0v? I had it wired through the brake light switch where the cruise would normally go, but it didn't feel right.

Aside from using a relay, is there an easier way to make this connection if it requires 12v when depressed?

Any help would be greatly appreciated!

[BR3W CITY]

I believe a change occured between gen III and gen IV and they switched around the wiring of the TCC lockup. IIRC, the brakelights were on=ground, so if the resistance of the tail lights isn't enough it may not know its on.

Do you have led tail lights at all?

[DLW]

It was my understanding you need 12v to lock the converter so you would want the 12v when the brake pedal is not depressed. Sounds like you already wired the brake switch right though using the cruise side of your switch to the PCM for 12v when brake is not pushed, right? Push the brakes then cuts power on cruise side and applies power on brake light side?

They do have this switch http://www.ebay.com/itm/TCC-BRAKE-SW...-/170795187396 which has a NO and a NC position on each side of the switch depending on position of the switch. This should be the same type of switch you already have I would think though.

Only other thing I can think of is the PCM to trans TCC wire not functioning or your existing brake/cruise switch works different than needed, there is only 2 wires that control the lockup I believe, PCM to brake pedal and PCM to trans, and of course there is always the tuning part or other issues like misfires, etc..

[aknovaman]

That ebay switch is available at autozone for about $12. Free at the local u wrench it.

[Hart_Rod]

GEN IVs are wired opposite of GEN IIIs, in reference to A6s, not sure about A4s....

[Smurfeh]

No Led tail lights, I had it hooked up to the Nc contacts on the break switch.. so when the brake is depressed 0v would go to the Tq Converter. This set up has made me believe the Tq converter is not locked up. The brake Switch I'm using is the NC NO contact switch that is there default on an 80's truck with cruise.

Based on Hart Rods statement, I assume everyone is giving me advice on the GenIII.. This engine is an LH6 GenVI I could run a relay through that brake like switch and have it power the coil on the relay I guess to kick the 12v to the Tq Convert when depressed.. but I was wondering if there was an easier way.

EDIT: Also, brake like resistance to ground .3ohms

[DLW]

In that case, it seems you will need the 12v when bake is applied and ground when not applied ..

Hart_Rod, did you use a relay and a 1K resistor to ground on yours? Do you need the relay or can you use the dual contact switch like I posted above , run ECM wire to brake light side (N/O), jumper that to the other side (N/C), and run that to ground with a 1K resistor without the use of relay?

I'm also going to tackle this in the near future so very curious myself.

[dayj1]

Originally Posted by Smurfeh

Based on Hart Rods statement, I assume everyone is giving me advice on the GenIII.. This engine is an LH6 GenVI I could run a relay through that brake like switch and have it power the coil on the relay I guess to kick the 12v to the Tq Convert when depressed.. but I was wondering if there was an easier way.

EDIT: Also, brake like resistance to ground .3ohms

Rob is 100% correct about the Gen IV being different (12V when brake is applied and ground when not applied). The easy way (no relay) is to splice the TCC wire into the white wire in the factory harness that goes from the factory brake switch to the tail lights.

If you do decide to use a relay, it has to ground the TCC signal wire when the brake is not applied or the converter still won't lock.

[DLW]

Originally Posted by dayj1

Rob is 100% correct about the Gen IV being different (12V when brake is applied and ground when not applied). The easy way (no relay) is to splice the TCC wire into the white wire in the factory harness that goes from the factory brake switch to the tail lights.

If you do decide to use a relay, it has to ground the TCC signal wire when the brake is not applied or the converter still won't lock.

If you use the TCC wire into the factory brake switch, is it a ground when brake is not depressed or open?

[dayj1]

Originally Posted by DLW

If you use the TCC wire into the factory brake switch, is it a ground when brake is not depressed or open?

When the brakes lights are off, the filaments are essentially low ohm resistors that "pull" the signal wire to near ground potential. There aren't a lot of Gen IV things that are easier than Gen III, but wiring the TCC is one of them

[Smurfeh]

Originally Posted by dayj1

The easy way (no relay) is to splice the TCC wire into the white wire in the factory harness that goes from the factory brake switch to the tail lights.

If you do decide to use a relay, it has to ground the TCC signal wire when the brake is not applied or the converter still won't lock.

I see what you're suggesting, paralleling the 12v when the pedal is depressed through the TCC wire and ground (white) but wouldn't that 12v go straight to ground instead of through the Tcc wire? thus creating the same situation?

[dayj1]

Originally Posted by Smurfeh

I see what you're suggesting, paralleling the 12v when the pedal is depressed through the TCC wire and ground (white) but wouldn't that 12v go straight to ground instead of through the Tcc wire? thus creating the same situation?

Nope. Current will flow through both wires (the TCC wire and the white wire to the brake lights). The easiest way that I know how to explain it is that both loads (the brake lights and the TCC wire to the TCM) are going to pull a finite amount of current that is dependent on the load. As long as the current source (battery + alternator) has enough capacity (read amps) to feed both loads, both of them will "take what they need".

[Smurfeh]

I read yah! That should work, leaving the other posts on the switch for cruise!
Love parallel circuits, the 12v will be constant but the amperage would split dependent on the load on both sides (TCC and Brake lights). Thanks I'll give it a shot and report on the results.

[DLW]

Thanks dayj1, I definitely over thought this. I see now you only need a resistor and maybe a relay if your using LED tail lights to simulate that bulb filament. Otherwise you can just run the TCC wire to a regular brake switch and your done...I was sort of miss-lead and thanks for clearing this up..