98-411 pcm plug n play option
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Joined: Jan 2026
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It has always been my opinion that an adapter of some type that mounts or plugs directly onto the 411 PCM and that the stock 98 harness plugs into directly is the way too go. This solution eliminates messing with and perhaps damaging the very brittle 98 harness that is now 20 years old.
Simple - indeed - if you have found a way. I have searched for hours and days, but have never found the plug to accomplish that method.
Finally - after all of these years waiting. Hope that you move forward with this project.
If there is some assurance of getting into the first group and also getting money back if the project fails - would be willing to make a deposit.
It has always been my opinion that an adapter of some type that mounts or plugs directly onto the 411 PCM and that the stock 98 harness plugs into directly is the way too go. This solution eliminates messing with and perhaps damaging the very brittle 98 harness that is now 20 years old.
Simple - indeed - if you have found a way. I have searched for hours and days, but have never found the plug to accomplish that method.
Finally - after all of these years waiting. Hope that you move forward with this project.
If there is some assurance of getting into the first group and also getting money back if the project fails - would be willing to make a deposit.
Teching In
Joined: Nov 2017
Posts: 30
Likes: 5
I have been rethinking this for a couple years and I think you can do this method if you are fairly handy with a soldering iron and wiring.
Get a set of loose 411 red and blue connectors from eBay.
Disconnect your battery.
Unplug the 1998 PCM.
Carefully remove the front cover from the 98 PCM (4 screws).
Now, disconnect and unsolder the two input connectors from the circuit board, separating the end plate and connectors from the 1998 PCM as one whole piece.
If you can isolate the connectors from the end plate, do so if you wish, but this means you wont have the bolt connection to be able to resecure the connectors to the end plate, so go forward however you see fit at this point.
I'll admit Ive never disassembled a 98 PCM so I don't know for sure if this is possible, I would suggest simply leaving the connectors attached to the end plate and reuse the bolt connection that holds the plugs tightly together with the end plate, it's your call here.
Now you have two 98 PCM input plugs, attached to the front plate or not these will reconnect to the stock red and blue harness connectors in the car still.
Plug them together now, or don't, your choice, I would think taking them onto a bench for soldering might be easier than doing it in the car like I had to do..
Grab your set of ebay 411 PCM connectors, trim the wires to see clean copper and prep for soldering, don't forget to use heat shrink on every wire you had to extend the length of beforehand.
From the car side of the harness you now have the front plate of the 98 PCM with the connectors exposed prepared for soldering on the wires from the two 411 red and blue connectors.
Familiarize and quadruple check your colors and pin locations, make a large drawing if necessary to help you visualize what you're about to do.
Make the appropriate connections from 411 red and blue connectors, to the back side of the 98 PCM input connectors, according to the wiring diagram for the swap.
Solder or use whatever method you see fit for long term reliability, and make sure to heat shrink any extensions.
Now its up to you how to make this harness neat and tidy.
You will want to seal the back of the 98 PCM connectors where you soldered or attached the 411 plugs from the elements somehow to prevent moisture and rain from the cowl getting down in there.
You have now attached the 1998 harness in the car, to the 411 PCM red and blue connectors, without cutting the original harness.
Plug the harness in to the car side first, then to the 411 second.
Don't start yet, instead plug your scanner or hp tuners in to make sure no instant codes pop up, if all looks good, turn the ignition on, wait a minute or so, listen for the fuel pump prime, and any other underhood sounds you're used to hearing with the old 98 PCM.
And of course, look around under the hood for any smoke, lol.
If all looks good, start the car.
If it's like mine it will start instantly and run perfect.
Now, Adapt the 411 to the 98 PCM bracket or make a new one, and try to keep the plugs facing down if possible to prevent water intrusion.
Good Luck!
Dave
Get a set of loose 411 red and blue connectors from eBay.
Disconnect your battery.
Unplug the 1998 PCM.
Carefully remove the front cover from the 98 PCM (4 screws).
Now, disconnect and unsolder the two input connectors from the circuit board, separating the end plate and connectors from the 1998 PCM as one whole piece.
If you can isolate the connectors from the end plate, do so if you wish, but this means you wont have the bolt connection to be able to resecure the connectors to the end plate, so go forward however you see fit at this point.
I'll admit Ive never disassembled a 98 PCM so I don't know for sure if this is possible, I would suggest simply leaving the connectors attached to the end plate and reuse the bolt connection that holds the plugs tightly together with the end plate, it's your call here.
Now you have two 98 PCM input plugs, attached to the front plate or not these will reconnect to the stock red and blue harness connectors in the car still.
Plug them together now, or don't, your choice, I would think taking them onto a bench for soldering might be easier than doing it in the car like I had to do..
Grab your set of ebay 411 PCM connectors, trim the wires to see clean copper and prep for soldering, don't forget to use heat shrink on every wire you had to extend the length of beforehand.
From the car side of the harness you now have the front plate of the 98 PCM with the connectors exposed prepared for soldering on the wires from the two 411 red and blue connectors.
Familiarize and quadruple check your colors and pin locations, make a large drawing if necessary to help you visualize what you're about to do.
Make the appropriate connections from 411 red and blue connectors, to the back side of the 98 PCM input connectors, according to the wiring diagram for the swap.
Solder or use whatever method you see fit for long term reliability, and make sure to heat shrink any extensions.
Now its up to you how to make this harness neat and tidy.
You will want to seal the back of the 98 PCM connectors where you soldered or attached the 411 plugs from the elements somehow to prevent moisture and rain from the cowl getting down in there.
You have now attached the 1998 harness in the car, to the 411 PCM red and blue connectors, without cutting the original harness.
Plug the harness in to the car side first, then to the 411 second.
Don't start yet, instead plug your scanner or hp tuners in to make sure no instant codes pop up, if all looks good, turn the ignition on, wait a minute or so, listen for the fuel pump prime, and any other underhood sounds you're used to hearing with the old 98 PCM.
And of course, look around under the hood for any smoke, lol.
If all looks good, start the car.
If it's like mine it will start instantly and run perfect.
Now, Adapt the 411 to the 98 PCM bracket or make a new one, and try to keep the plugs facing down if possible to prevent water intrusion.
Good Luck!
Dave