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Old 01-26-2006
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VSS and RABS Sensors

I am still working out the issues of doing the 2001 SOHC swap into my 1997 and I've hit another problem...there is no VSS sensor on the 2001. As many probably know, the rear axle speed sensor for ABS is used instead of the VSS sensor on the transmission after 1997. The signal from the sensor on the axle is sent to both the ABS computer and the GEM. The GEM then spits out a VSS signal for the other modules requiring it. I am swapping my GEM for other reasons, but I am using another 1997 GEM so that I do not have to completely rewire my truck. Is the VSS signal output by the 2001 GEM equivalent to the VSS signal from the VSS sensor on pre-1998 Rangers? The gauge clusters interchange so I'm thinking they are. If the VSS signal is the same, it seems to me that I could just mount the VSS sensor from my 1997 onto the 2001 TC and keep everything the way it is now without upsetting the PCM, cruise control, etc. Right now I am 2wd, but the 2001 transmission and TC will be going on for 4wd. Will the VSS sensor mount on the TC from the 2001? I know it's the same transfer case, but was it still made to accept a VSS sensor? I could always pull the TC from another 1997, I would just rather use the 2001 thats already on the transmission.

This may be more of a question for N3ELZ since he's a fellow electronics nut...what exactly is the signal coming from the VSS sensor? I understand the variable reluctance sensor used on the rear axle...those are pretty common and I have used them before, but the VSS sensor is a different type. I've always been curious about it, but too lazy to bring the portable scope out to my truck from work and look at it.

I know, a lot of reading and a lot of questions. Thanks for the help guys!
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Old 01-26-2006
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Early trucks:
speedo cable with interchangeable gears, no VSS.

1993? thru 97:
VSS signal generator on the trans (mounts in a position similar to a speedometer cable) I believe that it uses interchangeable gears for tire/axle correction.

98~2000:
VSS/ABS sensor on diff housing to either the GEM (RABS) or the 4WABS Module (4WABS). The adjustment for tire size is done in whichever of these modules is used for the VSS. The GEM or 4WABSM then outputs a corrected frequency to the PCM, speed control and speedo/odo. So in this setup, the PCM is just another "end user".

2001-on:
The VSS comes from a dedicated sensor reading a reluctor on the output shaft through a window in the transmission tailhousing. That signal goes directly to the PCM where it is corrected for tire size and axle ratio. The corrected signal is sent on to the GEM/SJB, speed control and speedo/odo. Here, the PCM is involved in developing the correct frequency for output to other components.

~~~~~~~~~~~

Since you are changing from a 2.3L to a 4.0L, you must be changing the transmission, too. I would try to get the engine, trans, PCM and engine/trans harness from the same donor truck. You would probably have to repin the 42P engine-to-enginebay connector but at least you would stand a chance of having the powertrain and speedometer work.

As far as the VSS signal type, I have never looked at it with a scope but it acts like a square wave on my DVM at low frequencies.
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Old 01-26-2006
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Oops...it looks like I read the EVTM wrong...again. Apparently I need to stop working on this after midnight so I don't read incorrect posts on RPS, get off on a problem that doesn't exist, and post stupid crap when I read the EVTM wrong at 2am. I really can read a schematic...I promise...it's my freaking job.

I see the output shaft speed sensor that goes straight to the PCM, my mistake was that the GEM only sees the rear ABS sensor on trucks with a 2.5L. So on the 4.0L, the PCM is only getting the OSS signal and it then makes the VSS signal for the rest of the truck based on the OSS, right? It looks like then there's no problem at all. I just wire the OSS sensor to the PCM and everything else to the VSS line coming out of the PCM. Do I have it right finally?

I am changing the transmission and I am getting the entire donor truck minus interior and other unrelated things so I will have the entire engine bay, fuel system, etc. At the moment I am thinking I will just rewire under the hood with the PCM harness from the donor truck. I am mostly keeping 97 wiring in the rest of the truck, that's why I'm trying to figure out issues like this one...which turned out to not be an issue. Thanks for keeping me straight...again.
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Old 01-26-2006
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I just thought of something else. There are three types of EFI fuel delivery systems in Rangers.

Return type (2 fuel lines)
Mechanical Returnless (1 fuel line)
Electronic Returnless (1 fuel line)

The type of fuel pump and lines used must match the PCM and engine. You'll need to research that and find out which system your truck has and which is on the donor. So you might need to swap those out, too. Chances are that they are different.

Maybe the evap canister and hoses as well since the donor may have Onboard Refueling Vapor Recovery and you 97 probably does not.
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Old 01-26-2006
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I already planned on basically swapping the entire fuel system anyway. Even if they are the same type, the lines from the filter to the engine are different and I need the pressure sensor in the tank on the donor since mine doesn't have one. Since I'll have everything anyway and the parts in the 2001 will be newer, I plan on swapping it all out no matter what. Thanks for the tip...any help is always appreciated. I'm trying to figure out all of these little things before I start so it will be as painless as possible. Having other brains to think of things I may have overlooked really helps.
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