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Discussion Starter #1
I was having spark advance issues so I swapped the pcm from a '96 Blazer into my '96 SS. It solved the advance issue and the tramsmission provides a nice kidney punch when it shifts. The problem is that the abs and brake light on the dash are on. I tried to clear them with my scanner but no luck. Any ideas?



And no.....black tape won't work...lol
 

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I'm Not sure on the older black pcm but on the newer ones they need to be vin matched,a while back my friend pulled a junk yard pmc and sent it to wait4meperformance, when he told them that it wasn't from his blazer on the phone they said they needed to encode it for his vin or something. You might want to try calling them i think they don't even do mail in anymore and just do a core charge.
 

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^^^ sounds like a passkey thing your talking about.

I know some (most actually) vehicles with ABS modules do communicate with the PCM. I had the same scenario with an '05 saffari but I replaced the ABS module/controller and it had to be programmed. The ABS light on that van was actually controlled thru data lines to the cluster from the PCM. I can't imagine that your 96 works the same way but possible. Reflashing may be the cure.
 

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Try putting the old PCM back in and see if the ABS and Brake light go out. Could just be a coincidence that they came on at the same time. A common problem, as you know, is the soldering on the boards in those EBCMs. That will make both brake lights come on. I would think any problem with the PCM would only cause the ABS light to come on. But you never know? Does your scanner give any ABS codes?
 

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Discussion Starter #5
EBCM? are you talking about body control module? I don't have one. No codes. It runs stronger than ever since the pcm swap. I'll try swapping it out again and see if the lights go away. If worse comes to worse ill find someone that can either fix the light issue, or see if they can figure out why my spark advance is so rtetarded....literally. I don't have the expertise do do a 411 swap or else I would consider it.
 

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Discussion Starter #9
I bet its just a single pin difference for the brake input wire between the blazer and the truck. putting the original pcm back in might confirm this.
I'm going to swap them out again to check. The abs harness has it's own connector on the pcm. There are four pins in the connector...I'll check the connection pin count.
 

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Discussion Starter #10
I was wrong on the pin count...both have five pins, and the old pcm made the lights go away. That suggests to me the problem is the pcm. I'll check with the dealer and see what a fresh program d/l would cost. For the time being...electrical tape it is over the lights...lol.
 

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Discussion Starter #12
I mis spoke about the pins....both ecm's have 5 pins, the harness however only uses three of them.
 

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for clarity I wasnt basing the 97 pcm thing on your pin count, I was basing it on that link I posted. the 96 pcm has abs functions built in, the 97 pcm will plug in but doesnt have abs functions. a follow up search says your issue, abs and brake lights on, is likely a problem from having a 97 pcm installed in a 96, because others have had the same issue.

I know you probably know this but its worth saying, a production date of say >6-96 will actually be a 97 model year vehicle, they start selling the new models in august. I owned a unicorn once too, a 98 4 cyl, the column wiring is slightly different by a couple pins and it sucks trying to find a gauge cluster. I tried swapping to a tilt column and had to reuse all the turn switch and ignition harness.
 

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Discussion Starter #14
I'm at a loss why the 97 pcm would have the connection for the abs plug. I'll get if figured out. The dealer was less than helpful. They won't program unless the vin matches. What happens if the pcm isn't repairable...what do they use then? The biggest problem is there doesn't seem to be much support for the black box, and I don't have the skills to swap to the 411
 

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this is what I think you are asking.

The ’97 truck uses the same computer as the ’96, but it has a separate computer that controls the ABS which is a different unit than the ’96. The ’97 truck needs the 5th (small) connector from the stock harness retained when the stock truck computer is kept. This connector can simply be removed from the stock harness and plugged in when the new harness arrives. The 5th connector has a single wire in it that simply loops around from one hole to another and pretty much does nothing except tell the computer that it’s there.
 

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Do the two pcms have the same part number?
What scan tool do you have?
Have you tried the ss pcm on the blazer?
 

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Discussion Starter #19
I don't believe the part numbers are the same. I'll post pics later today. The engine in my truck came from a 96 Blazer along with all of the accessory parts. Now that I think of it, I have the harness also. I'll check the abs connector on it also. Headed down to Vancouver in a little bit and will check when I return later today. My scan tool is from Harbor Freight. I didn't feel the need to break the bank on a scanner. It does abs...just not mine...
 

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The ’97 truck uses the same computer as the ’96, but it has a separate computer that controls the ABS which is a different unit than the ’96. The ’97 truck needs the 5th (small) connector from the stock harness retained when the stock truck computer is kept. This connector can simply be removed from the stock harness and plugged in when the new harness arrives. The 5th connector has a single wire in it that simply loops around from one hole to another and pretty much does nothing except tell the computer that it’s there.
Typical GM, in 98 they removed it. So that 5th connector was a 1 year only thing. Only the 97 had the 4 big (red,blue, white, and black connectors and the little jumper wire.

EBCM is the brainbox part of the ABS pump that the wiring connects to.
 
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