View Full Version : 98 Grand Prix Engine wiring diagram

03-20-2007, 05:34 PM
Looking for a 1998 Grand Prix wiring diagram, Engine diagram or complete car diagram will do... I really just need to compare ECM pinouts and the physical engine circuits. So I can see if I could possibly wire in a 98 ECM to gain more engine controls for a tuning aspect.

"Engine Performance" section of the system wiring diagrams would be ok... as noted I really just need to see the circuit layouts to compare and definitely be able to see the pinouts of the Blue and Clear connectors.

03-23-2007, 11:29 AM
I hear the 98/99 monte carlo/lumina harness is the best swap if your original engine/trans was a 3100/4t60e.

I have my spare 95 3100/4t60e wiring harness already spliced upto a 98 lumina harness plus the lumina pcm. BT racing did it for me. Check out the forum on www.motorswap.org

03-23-2007, 03:40 PM
I'm not swapping harnesses again.... I just want to re-pin the ECM plugs if possible and use the newer 98 ECM... that’s why I need wiring diagrams for the best donor...

Bottom line I want a 98 3100/4t60e combo car wiring diagram so I can compare circuits.

I figure if I go with 98 then it is less likely to have all the new BCM controls and hud stuff and whatnot.

3100 MPFI
06-01-2007, 09:17 AM
I know this is late, but I have a complete 1999 Grand Prix wiring diagram.

Is that something you can use? I should warn you. It SEEMS to be sound as far as the engine goes, but a lot of it is marked PROTOTYPE.

06-01-2007, 10:19 AM
I have '98 Lumina PCM pinout diagrams at home. I'll have to scan them though, and my only scanner is at work. So I can have them up for you on monday if you still need them.

This is something I was planning on doing too, but there are a few issues to deal with. first thing that comes to mind is the '98+ uses a pressure sensor for the fuel tank, and the PCM uses that reading to determine when to open up the EVAP purge solenoid. I don't really think there's much more to deal with, other than every PCM pinout being different.