Hey guys, I just thought that I would start up another article on how to do a resistor mod to an OBD1 computer. This is a needed (not required) mod if you put an OBD1 computer in your 96-97 LT1 car. If you do not do this mod, you will have to replace the knock sensor. And with as hard as these are to bleed, you don't want to lose any antifreeze lol.

The resistor that I will be using is a 1/4 watt 3.9k-ohm resistor. Actually, the one that I'm using is a 1/2 watt, but 1/4 can also be used.

Where To Buy

There are a lot of places that you can look for a used computer. eBay, Craigslist, even here on the site. They should run you less than $100 at most places. If you can find someone that doesn't know their value, then you can get a steal on them.

Why Do The Conversion

There are a few reasons that you can do this mod, and I use these excuses lol. The first is there is a lot less monitoring of the motor. This means less SES lights, but this can also be a bad thing. The second is ease of tuning. OBD1 computers are a lot easier to tune than OBD2 computers. The third reason is cause the software is a LOT cheaper. So, if you want to tune your car yourself, and you want to save a little money, this mod is for you.

You also don't have to replace the knock sensor if you decide to put your OBD2 computer back in the car.

Tools Needed

There are a few tools that you will need in order to do this. I can't remember the size (cause it's rubbed off my screwdriver lol) but you will need a torx screwdriver to remove the case screws.

You will also need a GOOD Soldering Iron!!! The iron needs to be able to get pretty hot, and have a small tip. To give you an idea, I did all of this with an adjustable iron set at 850*F. The old solder on the board needs a lot of heat in order to "tin" the joints. After that, you can turn it down to about 650*F.

Lets Get Started

Okay, here is a pic of what the computer will look like when you get it. There is some white corrosion on it, but this is normal. It happens when water hits aluminum and is not cleaned off. I put the sticker on there cause the OBD1 and OBD2 computers look exactly the same. I just didn't want to get them mixed up.

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The first thing you will need to do is remove the 6 screws that hold the case together.

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After you get those out, you will need to get a small screwdriver and pry the case apart. It will be stuck, so you will have to pry rather hard. BUT, do not pry too much. there are rubber cushions that hold the boards from hitting each other. If you pry too hard, you can rip the traces right off the board.

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When you get the case open, this is what you will see. If the gasket is on the other side, you will have to move it to look like the picture below.

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Here is a closer look at the board that we will be working on.

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Now, as I mentioned above, you will need to tin the joints where you are going to solder the resistor. I have pointed out the two sockets that you will be working on.

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Here you can see those two joints after I put some solder on them, fresh solder mind you, not the stuff that is 15 years old lol.

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Now, all you have to do is have a steady hand, and solder the resistor into place. After you solder it in, you can put some hot glue on it to make sure it doesn't move, but I don't think I will have a problem so I didn't do it. After you are done soldering, this is what you will end up with.

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Now like I said, you will need a good, hot iron. But, you don't want to hold it on the board for too long. If you hold it there for an extended amount of time, you can damage the board.

After you solder the resistor on, all you have left to do is put the case back together and put it in your car. That is the only change you will have to do in order to make your car run with your new OBD1 converted computer.

If you have any questions about any of this, feel free to ask.

 

What is OBD11?

But yes, that resistor is the onlything that you have to do other then tuning your car. The knock sensor for the OBD2 cars has a different resistance than the OBD1 cars. This resistor makes the computer think that the OBD1 knock sensor is installed.

 

Glad I could help out!

 

Nice.

 

I'm glad I could help out.