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Piggy backing Terminator X w/ stock ECU, 2000 F body
This is something I've always been interested in doing but since the Terminator X has been released it's really peaked my interest.
I don't want to rip all the wiring out and re wire the whole car. I'd like for the factory dash, BCM, ABS, etc to work.
What does the stock PCM NEED to see to keep the rest of the car working? I'm guessing at a minimum the crank and ETC sensor. I've read that you have to split the crank sensor signal to the Holley ECU and the stock PCM, but you need to figure out what resistor you need to use and have to use a scope to figure that out. I'm kinda confused on this part of the whole deal.
Why piggy back a Holley ECU you may ask? For what it is going to cost to buy HPTuners, the progressive nitrous controller I want, it's cheaper to buy the Terminator. Holley's software is easy to use and I'm pretty familiar with it. Added WB control, nitrous controllers, all the safeties you can set up.
There was someone that did this a month or so ago. I replied in his thread now I can't remember which thread it was.
Man, I hope you get it all lined out, as once done it will help a LOT of guys in the same situation as you.
I think with the price point of the Terminator, a lot of people will start doing this. I kinda hope that everyone can get together in this thread to help each other out.
I think with the price point of the Terminator, a lot of people will start doing this. I kinda hope that everyone can get together in this thread to help each other out.
Well if it CAN be done, it WILL be done! This forum is a great gearhead community with a real penchant for helping each other out.
I get a case of warm fuzzies here and there reading about the help passed out to anyone needing it.
Why piggy back a Holley ECU you may ask? For what it is going to cost to buy HPTuners, the progressive nitrous controller I want, it's cheaper to buy the Terminator. Holley's software is easy to use and I'm pretty familiar with it. Added WB control, nitrous controllers, all the safeties you can set up.
I have no experience keeping the stock dash working but I have to ask why you want it to work? Yes the 7" LCD is expensive and the 12" is insane ( I still bought one lol) I installed Holley EFI (Dominator) on my 2000 S10 and gutted all the engine wires except the starter wire, I also switched from auto to manual trans. The BCM is fully functional, Power locks/windows/courtesy lights/radio shuts off when door opens... what didn't work was key fob to unlock/lock the doors although the alarm still works if you lock the doors with the power lock button on the door ….yes it goes off every time until I put the key in the ignition and try to start the truck. The clutch still has to be pushed before it will it will energize the starter.
I don't miss the stock dash in the slightest, The LCD screen displays more than I could ever need and having the virtual toggle panel is nice. You can also setup the gauges to so they show peak numbers so at a glance I can see what my peak boost was along with RPM and anything else I desire. What better way to see any possible issues/warnings than to have it right in front of your face. Yes the dash is expensive but I couldn't drive without it now.
Last edited by LLLosingit; 05-31-2019 at 11:41 PM.
Because I want the interior of the car to look stock. I agree the Holley dashes are bad *** and do a lot of things. Just not the direction I want to go with on this car.
Because I want the interior of the car to look stock. I agree the Holley dashes are bad *** and do a lot of things. Just not the direction I want to go with on this car.
That's understandable. I looked into keeping the stock dash and even talked to a couple people that have done it but they were more interested in making money off me rather than help me accomplish it myself so I got nowhere.
My understanding is your powered sensors (crank cam position) can be split since they are just voltage triggers. Need an additional coolant temp sensor. One for stock ECU one For AM controller. May also need second oil pressure sensor.
Stock ECU does not need to see:
Fuel injectors
Coils
Oxygen sensors
Map
Maf
IAT
Throttle stuff
From what I've heard/read there's issues with splitting a crank signal but I can't remember why. I "think" the issue is when trying to split any 5v circuit. Does the this PCM use a 12v or 5v crank sensor? I think they switched to a 5v on the later model stuff. Only reason I say that is depending on what crank sensor you have when picking the correct Holley harness, some are 12v and some are 5v. I can look at a wiring diagram to find out.
I don't know if the OPSU goes directly to the the cluster or if it goes through the PCM. Same for the coolant sensor.
I would add a second OPSU down by the oil filter for the Holley. That way I could set up a safety if I loose oil pressure.
I'm about 98% sure the Holley won't drive the factory tach.
I'm going to print out some wiring diagrams and figure out exactly what the PCM drives.
I appreciate everyone's input. If I have mispoke about anything I will go back and change it.
So it looks like the speedo and tach are driven by the PCM. The speedo is tied into the cruise control module and from what I can tell from the wiring diagram the EBCM is also which would make sense
The OPSU goes directly to the the cluster.
The low engine coolant light strangely enough comes from the BCM.
I'm guessing the engine temp comes from the PCM, i can't tell from the diagram. However as we all know the coolant temp gauge on these cars are pretty much worthless. I think 98 was the only year that was actually accurate.
It would be awesome to get this to work. Im definitely interested in the system. For my setup, if I could get the tach, speedo, and fuel gauge working, I'll have the 3.5 screen to look at everything else.
It would be awesome to get this to work. Im definitely interested in the system. For my setup, if I could get the tach, speedo, and fuel gauge working, I'll have the 3.5 screen to look at everything else.
look at the c200 c210 circuits. Those come into the car from the engine harness. They carry most of the gauge information.
I'll have to check that out. Thank you.
I've posted a similar thread on the Holley board. There's a guy who said he did this on his C5 and just split the CKP signal wire from the factory harness to the Holley harness. One of the mods on the board, Danny, said if it's a Hall effect sensor(which I believe it is)that's all you have to do. However if it's mag sensor(GM wiring diagram says it is)you have to add resistors when you split the circuits so they will read correctly.
I haven't decided if I'm either going to strip down my engine harness or find another one and strip it down. Having the stock harness and the Holley harness is going to look absolutely horrible not to mention the lack of room in the engine compartment.
VATS definately will be turned off in the stock PCM before I start any of these shenanigans.
Before anyone starts throwing stones at me.....there is another way to do this that is super simple to hook up. I made a handful of these last year for a couple of Cummins swaps he was doing into GMT400's,800's and 900's. He wanted a way to piggyback the vehicles stock pcm so that every thing in the truck worked but do it with an 8 volt 2x square wave crank sensor. There wasn't much interest in them at the time and Cummins swaps into newer trucks are not exactly what I would call common in comparison to the amount of LS swaps that are done but for what it sounds like you guys are wanting to do this might make your lives a lot easier.
The idea behind the module is simple, read a pulsed input....like a tach signal...or an injector pulse etc and turn it into a engine specific wave form that a stock PCM would read as a crank signal. It took a lot of work but in the end I was able to keep the input and output signal RPM synced to 6K RPM with less then a 30ms delay in the signal conversion.
12 Valve Cummins feeding a 0411 PCM with the 24x crank signal
From what I've heard/read there's issues with splitting a crank signal but I can't remember why. I "think" the issue is when trying to split any 5v circuit. Does the this PCM use a 12v or 5v crank sensor? I think they switched to a 5v on the later model stuff. Only reason I say that is depending on what crank sensor you have when picking the correct Holley harness, some are 12v and some are 5v. I can look at a wiring diagram to find out.
I don't know if the OPSU goes directly to the the cluster or if it goes through the PCM. Same for the coolant sensor.
I would add a second OPSU down by the oil filter for the Holley. That way I could set up a safety if I loose oil pressure.
I'm about 98% sure the Holley won't drive the factory tach.
I'm going to print out some wiring diagrams and figure out exactly what the PCM drives.
I appreciate everyone's input. If I have mispoke about anything I will go back and change it.
The Gen3 ECUs use a 12v reference for the crank and cam sensors. The Gen 4 use a 5v reference.
05-31-2019, 10:49 PM
Piggy backing Terminator X w/ stock ECU, 2000 F body 
