JL_94z28

iTrader: (6)

I’ve run into LOTS of issues with tuning my 383LT1 this summer. I’ve tested all the grounding pins, but continue to have issues successfully flashing the PCM once we’ve brought the car to operating temp & have made a handful of dyno pulls. I’m starting to question the integrity of my 18yr old factory harness. It looks heat soaked and brittle in several spots. I’m seriously paying consideration to buying a painless wire harness at this point! Has anyone used a painless kit, or replaced their factory harness with an aftermarket one?

96TransAmboosted

iTrader: (8)

Why not just replace with another harness? Would be much cheaper than a painless.

JL_94z28

iTrader: (6)

I've checked most of the scrap yards around me & I've found most of the LT1 cars have been stripped of the drivetrain, PCM and harness. I haven't looked here on LS1Tech though yet. I'm not a fan of eBay, but open to looking else where.

merim123

iTrader: (11)

you are having an issue flashing your pcm?

stevo9389

i replaced my harness one in very good condition (was donated from another car using a megasquirt setup for a few years) and it didnt solve the issue. prolly cab wiring. found some wiring diagrams and ended up making a harness to tune with the PCM out of the car. didn't have a sufficient enough power supply so for the time being it connects directly to the battery but it gets the job done. all it cost was the $5 for the pcm connector ends plus some wire.

as an alternative you can try cutting right into the serial data wire at the PCM and run a new one directly to you obd connector to bypass the dash wiring. did this with a friend that switched from obd2 because of wiring issues and it worked great

JL_94z28

iTrader: (6)

Yes, programming the PCM is the issue. Through a few other threds, it seemed as though the problem was grounding. I've made sure that wasn't case & to my surprise.... a few pulls in yesterday on the dyno, we crashed my second PCM. Studied the painless kit online last night, it appears that they keep the PCM seperate from most of the cab wiring. Seems like the harness has all 4 connectors & only includes things like Injectors, Opti, Coil, Ignition, knock sensor, temp sensor, throttle body sensors, MAF, OBD1 dash port (and a bunch emission stuff I no longer have). I don't mind spending the $, if I knew it was the solution.... hate to toss $700 down the drain & and smoke a third PCM on the dyno. This car has a demon in the wiring somewhere! I'd love to hear more about stand alone wiring to bench program too. How many lines does the obd1 set up us for communications? I could hit a junk yard and pick up the pcm & obd1 connectors cheap!

LT1FirebirdSLP

iTrader: (2)

I just replaced my harness in my LT1 and it wasn't too difficult, albeit the motor was out of the car but if I was going to really swap out a harness because of PCM issues, I would prob convert to a LSx PCM and convert over.

merim123

iTrader: (11)

if you want a new harness, why not have speartech build you one then, i think you'd be better off than getting a standalone and trying to integrate it.

96lt1m6

iTrader: (31)

+1 for the Ls1 pcm conversion...
www.eficonnection.com

stevo9389

here is the one i made


here is what i used to make it (don't know who to credit for this)