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98 LS1 M6 wire harness options

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Old Mar 6, 2007 | 07:37 PM
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Default 98 LS1 M6 wire harness options

Hi,

I purchased what I was told was a '98 LS1 out of Trans Am. The engine is complete minus the harness, and I have the ECM/ECU (whatever GM calls it).

I have found out that the '98 uses a wiring harness different from that of the 99+ engines.

First of all, how do I verify I have a '98 engine and computer? I don't want to hunt down this hard to find harness only to find out in the end my engine isn't really a '98 and it won't work.

Secondly, what exactly is different about the harness?

Is there a way to modify the later model harnesses to work? The engine is going in an RX7, and will remain stock. I don't understand what these rewired harness I see on ebay are good for, or why I should spend the money on them.

What is my best option, aside from spending $1,000 on a new harness from Painless or wherever else I've seen them? I was hoping to get the harness for a couple of hundred bucks.

I've been reading and searching for the past few weeks, and I haven't really been able to narrow anything down past what I already know about 98 vs 99+. Thanks for any help you can give me!!! I really appreciate it.
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Old Mar 6, 2007 | 07:47 PM
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Probably a good idea just to switch to a 99+ harness and PCM. You can search for more info.
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Old Mar 6, 2007 | 07:52 PM
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Thanks Stealth. Can you link me to any specific info? I tried to search, but only one or two threads are coming up, and one of the is the one I just created. I've never been a fan of this forum software, specifically because of the generic search results that are returned, but this seems to be the best LS1 forum from what I can tell by trolling.

If you can point me in the right direction I'd really appreciate it. I'm hoping a thread exists with a comprehensive set of data rather than piecing all this knowledge together bit by bit from various threads on various forums. I think I might end up confusing myself in the end.

Thank you!
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Old Mar 6, 2007 | 10:08 PM
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The entire pinout of the 98 and 99+ harnesses are completly different. There are schematics of the pinouts on this board, but I forgot what section. You can tell by the color wire and pin.
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Old Mar 6, 2007 | 10:25 PM
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The pinouts and wiring info is posted in the FAQ sticky.

That will help to ID the wiring harness, but it won`t help ID the computer. I`m not sure how you would ID the computer.
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Old Mar 7, 2007 | 02:55 AM
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the 98 pcm looks way diff then the 99+ i would upgrade to the 99+ pcm/harness.
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Old Mar 7, 2007 | 06:07 AM
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Jonathan,

Ahhh yes....I can remember when I was but a young jedi...And I have come a long way since this thread https://ls1tech.com/forums/conversions-swaps/543016-69-ls1-camaro-newbe-questions.html , check it out, I went through the same thing. I modified my own wire harness (with help from G-Body and others) and I have a 'easy to read' schematic in the sticky section for the 98.

ChrisP
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Old Mar 7, 2007 | 08:33 AM
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It's been a while since I've seen a 98 PCM, but if I recall correctly the whole case was cast aluminum and the 99+ cases are half cast aluminum, but have a shiney plate on one side. The best way to check will be to go find a pinout in the stickey section and make sure though. You can also look at the coolant temp sensor that is at the front of the drivers side head. 98s have 3 pins in the connector, but the later motors only have 2.
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Old Mar 7, 2007 | 01:31 PM
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Originally Posted by SICMARO
the 98 pcm looks way diff then the 99+ i would upgrade to the 99+ pcm/harness.
How do I go about doing this? Keep in mind I have no harness right now, so me buying a '99+ harness wouldn't set me back any more money than trying to hunt down a '98 harness.

Can I just grab a '99+ PCM and a '99+ harness, plug it all up and be good to go as far as functionality against the '98 engine?

Originally Posted by Skele4door
It's been a while since I've seen a 98 PCM, but if I recall correctly the whole case was cast aluminum and the 99+ cases are half cast aluminum, but have a shiney plate on one side. The best way to check will be to go find a pinout in the stickey section and make sure though. You can also look at the coolant temp sensor that is at the front of the drivers side head. 98s have 3 pins in the connector, but the later motors only have 2.
The PCM I have here in my hand is definitely fully cast aluminum case.

Originally Posted by Chrisp3
Jonathan,

Ahhh yes....I can remember when I was but a young jedi...And I have come a long way since this thread https://ls1tech.com/forums/showthread.php?t=543016 , check it out, I went through the same thing. I modified my own wire harness (with help from G-Body and others) and I have a 'easy to read' schematic in the sticky section for the 98.

ChrisP
Regarding your thread about your car/engine and the valve cover bolt position, I noticed someone mentioned a laser etched number on the back of the block by the oil filter. Is there a list somewhere that cross references that number against a VIN or against a year listing for the engine? I want to be 100% sure on what year engine I have. 90% sure it's a '98...but I want to be sure.

Thanks a bunch guys. In the meantime I'll try to do some more reading up.
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Old Mar 7, 2007 | 03:08 PM
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I believe that my '98 LS1 had a 1998 date lazer etched on it....somewhere. The PCMs are way different.
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Old Mar 7, 2007 | 04:19 PM
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Well my heads have a very long digit number etched into them. Probably 16 or 17 characters long, and the first two digits are "98". Could that be it?
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Old Mar 7, 2007 | 05:43 PM
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You're in luck. I have a '98 M6 harness complete out of an F-body. If you want it, send me a PM.
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Old Mar 8, 2007 | 07:35 AM
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If you are doing the RX7 swap you might want to check this forum out.
http://www.torquecentral.com/forumdisplay.php?f=11
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Old Mar 8, 2007 | 08:36 AM
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Speaking of 98/99, I have a 98 PCM and auto harness, and I would love to swap it out for a 99+ pcm/harness ...
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