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rpmdiag, Tech and Instructor
Category: Classic Car
Satisfied Customers: 7870
Experience:  Since 1975
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2005 CVPI 4.6L installed in a 1955 Ford F100. Truck has a

Customer Question

2005 CVPI 4.6L installed in a 1955 Ford F100. Truck has a mustang 2 front suspension with power steering rack. It also has an aftermarket steering column.
Will there be computer (or other) problems if I eliminate the variable assist steering modules and circuitry.
I've read that the pcm will be affected and the engine might not start.
Please advise.
Submitted: 1 year ago.
Category: Classic Car
Expert:  rpmdiag replied 1 year ago.

Hi, I’m Ron and I can help you.
I have been in this business since 1975 and also teach automotive repair. I am confident
we can resolve your problem together. Please understand that I don't know your skill
level. I can't see, smell, hear, or touch the vehicle either, so it may take a few replies to
get to satisfactory results. Please be patient!
I also try to give all of the information you may need, expecting a “positive rating” in
return. I will also continue assisting you after you have rated me, if necessary. If there
is any reason I cannot get a positive rating, please let me know why “in advance”, so I
can go another direction for you. I am sorry you’re having this problem; I’ll help you
through it.

You read it right, trying to alter a system that has these functions are all a part of the computer system. HOWEVER, if you're fortunate enough to find a tuner in your area, he can give you what you ask for through programming it your way.

Thanks, Ron

Customer: replied 1 year ago.
I understand that a pcm can be reprogrammed but .... very few techs have any experience doing the reprogramming that would be necessary. I have all the CVPI wiring schematics and have over 30 years of "electronics" experience and over 50 years of automotive experience. What I don't have is the internal circuitry for the pcm to see how it could be adapted to eliminate the variable assist feature and it's circuitry.From what I've researched, there may be some sort of signal that is received from the variable assist sensor, power steering sensor (or module) that will cause the pcm to read a "failure" and will not allow the engine to be started. This is what I'm trying to ascertain.If I had an entire CVPI in running condition I could start unplugging wiring connectors and see what effect it would have on the pcm and the other operating systems. I could also attempt to bypass the sensors etc. by providing the appropriate signal to "fool" the pcm. Unfortunately I don't .... and Ford factory service mechanics only know what they see on their computer and diagnostics screens. They are of no help.If I know that I can't safely eliminate the sensors (or the circuitry) then I will be forced to get a pcm and wiring harness from a previous model year that doesn't have the variable assist feature. That would be very costly for me and an expense that I don't want to incur.Can you advise?
Expert:  rpmdiag replied 1 year ago.

To get close to your goal, you need a scan tool that does bidirectional tests.



Customer: replied 1 year ago.
A scan/diagnostic tool is more expensive than getting another pcm and wiring harness (without the variable assist features) from an earlier model 4.6L at an auto salvage yard.I was hoping that you would be able to discuss the circuitry and related modules so I could just eliminate (or bypass) the circuits as necessary and keep everything else. Or, as an alternative, provide some input on the internal circuitry of the pcm and/or the circuit boards so I could modify them accordingly.
Expert:  rpmdiag replied 1 year ago.

That would be called tampering with a vehicle in a on stock fashion, and in most states is illegal.



Customer: replied 1 year ago.
I only know about the laws in about 3 states but .... historic vehicles can be modified to eliminate any pollution devices and anything else if a vehicle is to be "hot rodded". You can change engines, transmissions, drivetrains, suspensions etc and still be in conformance with any applicable laws and regulations. The only condition is that it is inspected and in a safe and driveable condition.Performance "chips" are allowed in most states as are other forms of pcm circuitry modifications. This is not tampering so long as the state and federal standards are met.Sorry you couldn't help.
Expert:  rpmdiag replied 1 year ago.

Sorry, maybe a tuner can help you. there are people out there that do mods like that, they're just hard to find.


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