does VSS signal effect trans?

greg454 · Sep 25, 2016

First off I also listed this question in the misc electrical section, but since it also effect the automatic transmission OD I thought I would put it here also.

My brother has a 99 ranger with a rather hard to pinpoint issue. 4.0L, Automatic, 4x4.
It will drive fine then with no warning the speedo goes to zero, the abs light comes on, and the transmission overdrive also goes away. The code reader says speed sensor so he has replaced it twice and the wiring to it. He also changed the instrument cluster as it had a couple bad gauges anyway, but the underlying problem still remains. So does anyone have a document or schematic of how the VSS signal is used and how it gets there? Or any other thoughts on this problem?

Thanks,
Greg.

RonD · Sep 25, 2016

Yes, loss of VSS will effect transmission on a 1999 ranger with automatic.

In 1999 there were two different paths for the VSS signal
If truck has 4 wheel ABS then VSS signal goes directly to the 4WABS module, it is then adjusted for tire size and rear axle ratio.
After adjustment the VSS signal is sent out to Speedometer, Cruise module and Computer, ABS module already has it

If truck only has rear ABS then VSS signal goes to RABS module AND to the GEM(generic electronic module), where it is adjusted for tire size and rear axle ratio and then sent out to Speedometer, Cruise module, and Computer.
So the VSS signal is shared by ABS and GEM/speedo

Since you are also getting an ABS light when speedo turns off I would say there is a wiring problem from VSS to cab/ABS module.
Assuming old VSS didn't show any damage then tone wheel in rear axle should still be OK, I would start by tracing the VSS wires from rear axle forward to ABS module

greg454 · Sep 25, 2016

Thanks Ron. Exactly the info I was looking for.

Greg

RonD · Sep 25, 2016

I edited it so reread it, RABS and GEM share the VSS signal.

These PDFs have the wiring for both versions, 1998 will be same as 1999
Rear Axle Sensor = VSS

greg454 · Sep 25, 2016

RonD said:
I edited it so reread it, RABS and GEM share the VSS signal.

These PDFs have the wiring for both versions, 1998 will be same as 1999
Rear Axle Sensor = VSS

Thanks again Ron. I probably cant look at it until next week, but it gives me a good idea on where to start looking. You don't by chance have a document showing how these cables are run and through what connectors by chance?

Greg

RonD · Sep 25, 2016

No, you would need the EVTM(electric vacuum troubleshooting manual) for 1999 Ranger for that info

greg454 · Sep 25, 2016

ok. Thanks.

Kenney007 · Sep 26, 2016

Thanks everyone for the help. (I'm the "little brother" who owns this cursed vehicle.) Two clarifications: (1) its the 3.0 liter version, and (2) I've already replaced the wiring from the VSS to the ABS module. The mechanic suggests the next steps are replacing the ABS module and/or the GEM, but is hesitant to do so because he says those are expensive and may not fix the problem. But is that my only option? I need this solved before the first snowfall (which is probably no more than a month away).

greg454 · Sep 26, 2016

Hey little brother,
I went to the local pull and save today and got a

GEM module F87B-14B205-EE
and
ABS module F59F-2C018-AA

Both for $35, so not too much to lose if there not the problem. If thats not a quick fix we will jump into wire tracing and VSS signals.

I got these from a 98 but I believe there the same for your 99. Maybe Ron knows the answer to that? I also dont believe they need programming?

And to clarify, the truck does have 4wabs, as did the truck I found in the junk yard.

The donor truck looks like it was in a fairly minor accident with airbags blown, so Im betting the modules are good

RonD · Sep 27, 2016

The rear axle VSS is a variable reluctance sensor, it generates its own AC voltage as the "teeth" on the tone ring pass by it.

So you can test VSS and its wiring using volt meter set for AC Volts, .5 to 1.5v AC will be seen depending on axle speed.

4WABS module would be first suspect, because ABS light comes on, which means it is either not reading all the wheel sensors or there is another problem, since speedo also goes off at that time then rear axle speed sensor would be common denominator so VSS or wiring, and since that was changed, then 4WABS would be next.

GEM gets the VSS signal from 4WABS module but in 4WABS models I don't think it modifies it, or passes it on, it needs speed info for 4WD
Speedo and cruise should get VSS signal directly from 4WABS module, not via GEM in 4WABS models, but can't say for sure on that

4WABS is programmed with revolutions per mile, since the tone wheel is reading axle revolutions not drive shaft revolutions the ring and pinion ratio doesn't matter for true speed calculation.
But tire size does
REV/MILE CHART
Tire Size = REV/Mile
P205/75/R14 = 00800
P225/70/R14 = 00794
P235/60/R14 = 00797
P215/75/R15 = 00750
P225/70/R15 = 00761
P235/75/R15 = 00721
P265/75/R15 = 00679
P245/75/R16 = 00681
P255/70/R16 = 00690

Shouldn't take someone with the software too long to change current 4WABS rev/mile number if that is needed

greg454 · Sep 27, 2016

Thanks Ron. Looks like im going to look at it next Saturday. Another question for you, I pulled parts off a 98 ranger 4x4 XLT. I didn't open the hood but verified it had wires going to the front wheel sensors. The ABS module I pulled from it was in the dash on the right side of the radio, the GEM was on the left side of the radio. After I got home and looked up the part number F59F-2C018-AA I am seeing this as a RABS module. Is there another 4WABS module under the hood I should of got? I'm a little confused about that. I have an oscilloscope so I will probably actually look at the signal to verify it is correct.

edit:
In hindsight I looked really quick under the front and saw the brake line and another line and assumed it was for a wheel sensor.. but it may have been a vacuum line for automatic hubs... I should of looked harder.

greg454 · Oct 2, 2016

Just a quick update. I swapped out the 4WABS module with a $35 junkyard unit and it seems to have fixed the problem for now. Time will tell.........

Greg

RonD · Oct 2, 2016

Good work

Thanks for updating the thread

does VSS signal effect trans?

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