Thread: Difference in engine harness for 97 GTP vs 98 GTP

I've got access to Alldata and pulled diagrams for a 97 Grand Prix VIN: K and 97 Grand Prix VIN: 1 (SC). They are the same diagram exactly without any variance.

I repeated the process with both models only for the 98 yr model and they are the same there too. They are however totally different from what is shown for the 97's.

Anyone have any ideas on this one? Are the 97 GTP harnesses the same as 98 harnesses?

I'm trying to figure this out because I'm contemplating doing a complete pin out on my current 97 GT harness and adding wires where needed to do my L67 swap. I know I have another thread about keeping my 4T60E and swapping to an HD variant, but now I'm thinking maybe I'll go ahead with a 4T65E-HD. I bought a 97 GTP computer this morning b/c I'm trying to keep it consistent between year models.

Originally Posted by That Canadian Guy

also......... anti canada forum?

Yea down here in Texas we really hate Canadians and Mexicans!!!!
jk.

The short of it is that our old site and owner sold out to a company based out of Canada. They added all the google ads and made some sweeping changes. As a result the core of the website moved over to a new site. The anit-Canadians things is just a joke. Its a good group of people!

The computers arent just plug and play though? Will a 97 GTP computer work with a 97 GT harness?

The long way of what I'm asking...
If I drop my L67 in the engine bay and hook up all the sensors, then plug in the 97 GTP computer to the 97 GT harness... will the motor run?

I know I have to run wires for the GTP map sensor and some say the boost bypass valve, but other than the transmission that's it... right?

Sorry for all the questions, but I have been researching this stuff and still haven't worked everything out.

Originally Posted by That Canadian Guy

it should work.

For the map you can just swap the harness and let it sit where ever you'd like.

you will have to extend the harness to get it to its proper bracket.

But that bracket clutters up the engine bay. As do all of the brackets minus the necessary ones.

x2 for the map just cut the old plug of and wire the l67 one on

Just for giggles, I put the GTP computer in the car just now and its a no go. The motor wont fire up with it installed.

This leads me to believe that it wont run when the L67 is installed either. I'm going to investigate this further, but I'm out of time tonight. Maybe this weekend I'll give it another go!

hmmm oh and tell hank hill i say hi lol jk

Originally Posted by nascartech

hmmm oh and tell hank hill i say hi lol jk

eh, well, dontcha kno. Ole Hank moved out aboot a year ago, dontcha kno.

So on a more serious note. I had a little time this evening to mess with the GTP computer again. After reinstalling it, I pulled out my scanner to see what was going on with the GTP computer.

KOEO- I noticed everything looked ok except that the MAP readings were really high, roughly twice what it was reading stock. I decided to see what the computer would do if I just unplugged it and tried to crank the motor. Without much hesitation, it started. The motor was running pretty rough when compared to the stock ECU, but hell the MAP was unplugged lol. I also noticed before starting it that there was a load on the motor of about 8% which was weird because the motor wasn't running. When its not running it normally reads 0% load. Also the MAF was reading like .6XX lbs of air when it would normally read zero with the stock computer. I justified this though for the time being because the GT computer readings were with the airbox completely closed and when I swapped the computers, I had the GTP computer sitting in the box with the lid off. I guess now I should have put the lid on...

So I guess the long of it is that the GTP computer will run a GT harness with a few tweaks... mainly the MAP sensor.

Maybe this is all old news for everyone here, but I had been looking every where for info on swapping a 97 GT to a GTP set up ie. L67, 4T65E-hd, etc. It looks like I can use the stock GT harness and just add a few wires and go. From what I had read before, I was under the impression that the wiring was all different and swapping everything was not worth it. If you want to do the swap, just get a 97 GTP computer, if you can find one, and then plug it in. You'll have the stock GTP tune, it works with the engine harness, and swapping a 4T65E should be fairly easy.

The next issue will be to tackle the 4T65E swap to replace the 60E that's in there. This doesn't seem to be so bad though. With the help of the Alldata wiring schematics ,which up to this point seems to be correct afterall, I'll be able to cut the connectors I need at the junkyard and I will just splice them in to run the new transmission. By splicing, I mean I have to run new wires since there aren't any. Since there is no performance shift option, I'll just have to have the transmission tables adjusted in the computer to make the changes needed to best suit my needs.

Well to sum it all up now. I'm sure the stock GT computer could have been reprogrammed with everything I needed including transmission controls, but I seem to have found a solution with getting the GTP computer from the junkyard. I shouldn't have to mess with finding a harness now either (since the donor car is hacked up) other than wiring connectors for the transmission. Everything I have read up to this point makes it seem like buying a GT and trying to swap in an L67 and 4T65E-HD is really difficult. Unless there is some type of monster lurking in the trunk, it seems to be pretty straight forward! Let me know now guys... am I making a mistake?

FWIW if you don't want to change the map connector, use an L32 map sensor.

Originally Posted by BillBoost37

FWIW if you don't want to change the map connector, use an L32 map sensor.

This is good to know. I'll probably go with one of the L67 adapter harnesses anyways so I'm not too worried about this, plus I have an extra L67 MAP taking up space in the garage. Might as well use it...

I'm going to add another note for anyone that comes across this in the future. ZZP says that the adapter they sell will use pin 77 on the clear connector for 98+ vehicles. After looking at my wire diagrams, this should be pin 23 on the blue connector for 97 models.

I'm going to start working on the diagrams for the tranny next so more info will follow.

***The following will show you the wires and where to pin them on the 1997 computer.***

14 Pin Connector to Transmission

D C B A

x x x x x x E

S R P N M L

x V U T

1997 Computer Pin Out Location:

Pin_____Wire Color___Circuit #________Pin Location for Computer
A________LT GRN______ 1222__________________Clear 11
B________YEL/ BLK______1223_________________ Clear 17
C________RED/ BLK_____ 1228_________________ Clear 61
D_______LT BLU/ WHT___1229__________________Clear 20
E__________PNK_______1039/839________________Blue 19 ***Splice into existing pink wire
L__________YEL________1227__________________Clear 71
M__________BLK_________808 _ ________________ Blue 56 ***Splice into existing black wire
N__________PNK________1224__________________Clear 27
P__________RED________1226__________________Clear 31
R_________DK BLU______ 1225__________________Clear 29
S_________RED/BLK_____ 1230___________________Blue 7
T__________BRN_________418___________________Blue 22
U__________YEL_________657___________________Clear 75
V_______DK BLU/ WHT____1231___________________Blue 46



I just want to say as a disclaimer, that this is what I have come up with after comparing harnesses both at the junkyard and using the info in Alldata. I have not yet tested this so please use at your own risk. I'm not responsible for any loss or damage you cause as a result of following this information. Once I have a chance to test it, then I will update the thread to let everyone know that it works!

I figured I would add one more post here.

My plan is to hopefully get a junkyard harness cheap. The harness will have to be intact to do what I want. The plan is to pull the 14 pin connector and accompanying wires all the way to the pins in the connector. I want to try this route vs running the wires so that it all stays factory. I will use loom and tape to really go for that factory look.

At the end of the day it will be a learning experience lol! I have messed with wiring before but not on this level. Although its pretty basic, I've never tried to build into a harness like this. It should be fun!

I'll be making some updates to the pin outs above so stay tuned for those if interested. I'm going to make this work!

To change from a 4T60 to a 4T65 you map the 7 existing wires and add 5 more.