Computer Diagnostics and Tuning Technical discussion on diagnostics and programming of the F-body computers

Internal PCM Resistor Mod: OBDII to OBDI Conversion?

Old Jul 14, 2007 | 08:19 PM
  #16  
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What all is needed to make a 97 use the obd1 pcm? Do you just unplug the obd2 and plug in the obd1?

Thanks for the help.
I have tunercats for the obd1 and may try converting a car for a friend
Old Jul 14, 2007 | 09:38 PM
  #17  
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Originally Posted by jakesz28
What all is needed to make a 97 use the obd1 pcm? Do you just unplug the obd2 and plug in the obd1?
Yes.

In addition, you need to do one of two things.

1) Solder in the resistor (as shown above) into the OBDI PCM
2) Change the knock sensor in the engine block (when the OBDI PCM goes in)

The problem with option 2 is that every time you switch between OBDII and OBDI, you need to change the knock sensor. With option 1, you simply add the resistor once to the OBDI PCM and you are all set. No other changes required.

Dan
Old Jul 15, 2007 | 12:33 AM
  #18  
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is the knock sensor on the motor a MUST for the 97 model? i am thinking about buying an OBDI PCM so i can tune it when i want with my Tunercat but still be able to put my OBDII ECU back in for inspections
Old Jul 15, 2007 | 01:25 AM
  #19  
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Taken from the post directly above yours:
Originally Posted by stereomandan
...you need to do one of two things.

1) Solder in the resistor (as shown above) into the OBDI PCM
OR

2) Change the knock sensor in the engine block (when the OBDI PCM goes in)

The problem with option 2 is that every time you switch between OBDII and OBDI, you need to change the knock sensor. With option 1, you simply add the resistor once to the OBDI PCM and you are all set. No other changes required.

Dan
If you read this thread from the beginning you should be able to find answers to most of your questions. There are even pictures of the modification you need to make to your OBDI PCM to avoid having to change the knock sensor.

If you make this modification you will have to do nothing more than change the PCM to switch back and forth between OBDI and OBD2
Old Jul 15, 2007 | 01:32 AM
  #20  
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thanks :P and thanks for making me look like an R-Tard :}
Old Jul 15, 2007 | 01:41 AM
  #21  
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You're welcome, and sorry, I wasn't trying to make you look bad, I know how hard it is to find info on this, been putting together stuff to do my swap for quite a while now. That's actually why I posted pics of my new PCM, to help anyone that might have been struggling like I was.
Old Jul 15, 2007 | 01:59 AM
  #22  
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was yers already like that? and how hard is it really to solder that resistor on there?
Old Jul 15, 2007 | 10:17 AM
  #23  
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Yes, mine was like that when I bought it, it was advertised here as an OBDII to OBDI conversion PCM.

It has a sticker on the outside from PCMforLess, so I'm guessing they did the resistor mod.

MadZ28 sells the conversion PCM here http://www.madtuner.com/index.php?pa...mart&Itemid=26

PCMforless has it on this page http://www.pcmforless.com/index.php?...d=44&Itemid=40

Their prices are $250-$275 but I believe that includes tuning.

How hard it would be to put the resistor in a stock OBDI would depend if you can solder. The parts on the board are fairly large, so if a person knows how to solder it would be a piece of cake. I intended to do this myself but a very reasonbly priced PCM with the mod already done came up for sale, so I bought it instead.
Old Jul 15, 2007 | 11:06 AM
  #24  
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would it need a tune from PCMForless or MADZ28 to make it work or do they charge the 250 for just that resistor?
Old Jul 15, 2007 | 12:32 PM
  #25  
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The cheapest way would be to solder in the resistor yourself and tune it with LT1_edit or tunercats. That's the whole reason I'm doing it anyway. Wouldn't be much point to the conversion if you were still going to pay someone else to do the tuning. The software for OBDI is way cheaper than the software for OBDII.

If you didn't think you could solder the resistor yourself and didn't know anyone that could do it for you, then you could buy the conversion from madZ28 or PCMforLess, kind of expensive but I believe you would get a tune with that, making it worth more. From that point on you could do your own tuning with the software of your choice.
Old Jul 15, 2007 | 03:18 PM
  #26  
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well i already have tuner cat and im sure either me my dad my cousin or my grand father could solder it on, so all i need it the resistor and the obd1 ecu :P
Old Jul 15, 2007 | 03:44 PM
  #27  
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Yep, you got it.
Old Jul 22, 2007 | 11:34 AM
  #28  
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ok all of you have 97's ? do you still have to convert to the resistor when doing this on a 96?
Old Jul 22, 2007 | 11:48 AM
  #29  
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Yes, you still do the resistor or change the knock sensor in the block. 96 and 97 are both OBDII.
Old Jul 22, 2007 | 11:57 AM
  #30  
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i knew thery were both OBD2 but i didnt know if the sensors were another gay GM change

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