A Guide for connecting a 1G TT ECU to a 1G/2G NA harness

[Tool Man]

Ok, I have a question. I'm in the middle of my conversion on my 94. Using a 1st Gen TT ecu and my 94 NA harness. The TT conversion car I'm using for the donor has a 1 O2 setup on it. The only o2 sensor is the rear one. The fron O2 Bung has a bolt in it. It's using the first gen tt ecu and harness. Should this work ok?

[Mr.3000]

I would run the two TT O2 sensors because the TT ecu is expecting two signals.

[green-lantern]

Originally Posted by Mr.3000

I would run the two TT O2 sensors because the TT ecu is expecting two signals.

oh yes! I would definitely use both O2 sensors. That is very strange that the donor only had one (could have been its demise)

[green-lantern]

Originally Posted by Tool Man

Ok, I have a question. I'm in the middle of my conversion on my 94. Using a 1st Gen TT ecu and my 94 NA harness. The TT conversion car I'm using for the donor has a 1 O2 setup on it. The only o2 sensor is the rear one. The fron O2 Bung has a bolt in it. It's using the first gen tt ecu and harness. Should this work ok?

updates TM, you really ought to start a thread.

[green-lantern]

Mr 3000, Please explain your edit.

**WHEN EXTENDING O2 WIRES, DO NOT SOLDER TWO WIRES TOGETHER! THE SIGNAL WILL NOT READ CORRECTLY! INSTEAD USE CONNECTORS**

I don't understand why that matters. I soldered mine so I need to change mine if it does.

Thanks

btw they have changed the way the fan controller is wired up. I just installed a new one this weekend. I can post up the difference and you can add it to the first post in your thread if you want to do that.

[Mr.3000]

Originally Posted by green-lantern

Mr 3000, Please explain your edit.



I don't understand why that matters. I soldered mine so I need to change mine if it does.

Thanks

btw they have changed the way the fan controller is wired up. I just installed a new one this weekend. I can post up the difference and you can add it to the first post in your thread if you want to do that.

Yes the only wires that you should never solder together are O2 sensor wires. Why? Well the signal actually gets destroyed by the solder which is really crazy. Yea I didn't figure this one out until after my car broke and the guys up at PCM saw that I had soldered them together. It is actually mostly a little known fact that solder messes up the signal.

I remember that whenever I tried to datalog using the stock O2 sensors, I was getting crazy numbers from them that weren't fluctuating properly and I never could figure out why. So I tuned off of my wideband instead and just had to deal with not being able to verify the results from my datalog. Little did I know that this would still cause problems from time to time because the factory ECU is still reading from those sensors and trying to compensate for what it is seeing and thus my tune would be off a lot of the time.

The way to remedy this is to use crimp connectors. Then once you connect them, wrap the connection so that it can never come loose.

[green-lantern]

Originally Posted by Mr.3000

Yes the only wires that you should never solder together are O2 sensor wires. Why? Well the signal actually gets destroyed by the solder which is really crazy. Yea I didn't figure this one out until after my car broke and the guys up at PCM saw that I had soldered them together. It is actually mostly a little known fact that solder messes up the signal.

I remember that whenever I tried to datalog using the stock O2 sensors, I was getting crazy numbers from them that weren't fluctuating properly and I never could figure out why. So I tuned off of my wideband instead and just had to deal with not being able to verify the results from my datalog. Little did I know that this would still cause problems from time to time because the factory ECU is still reading from those sensors and trying to compensate for what it is seeing and thus my tune would be off a lot of the time.

The way to remedy this is to use crimp connectors. Then once you connect them, wrap the connection so that it can never come loose.

It seemed like mine where working correctly (cycling) but also I have always felt like there has been something a little off. It could just be my imagination but anyway I will redo it and see what happens.

Thanks!!!

[levani041491]

i am getting to that and i have 1996 CALI-spec and it will be same ?? on body it says august 1995 and title says 1996 and i f i get 1G FED ECU can i use in cali-spec?

[Lohnes68]

i also have a question here. I have a 94 fed spec NA, if i put a TT 94 fed. ecu in the car do i need to change any wires or will it plug right in?

[Mr.3000]

Originally Posted by levani041491

i am getting to that and i have 1996 CALI-spec and it will be same ?? on body it says august 1995 and title says 1996 and i f i get 1G FED ECU can i use in cali-spec?

I'm actually not sure about this one. I haven't seen a Stock 3/S ECU in a long time haha. I do remember that the 96+ ECU's didn't seem to be compatible with the 1st Gen's because they had a different number of connectors. I would locate your ECU and find out if you have 3 or 4 ECU connections before proceeding any further. Also, due to the fact that you have a Cali Spec, I would err on the side of safety and go with a Cali ECU.

Originally Posted by Lohnes68

i also have a question here. I have a 94 fed spec NA, if i put a TT 94 fed. ecu in the car do i need to change any wires or will it plug right in?

No, this will not work. 94+ TT ECU's have 4 connections. Your harness only has 3. The only ECU's that are compatible that will allow minimal modification are the 91-93 TT's. Also, make sure you grab a Fed Spec