Thomas Jefferson
New Member
- Joined
- October 19, 2017
- Messages
- 4
- Reaction score
- 1
- City, State
- Seattle, WA
- Year, Model & Trim Level
- 1988 Ford F-150
Again, thank you for your response. Your answers led my in the right direction. I have been researching the issue using F-150 resources but I will confirm that the Explorer setup is the same re model years, etc., before I go forward.
For the F-150 anyway '92 was the introduction of the PSOM + RABS. The speed signal (vss/dss) went through the PSOM and RABS modules prior to going to the PCM and Cruise control modules. From '97-'98 the vss raw signal went separately (but the same unconverted signal) to the PCM; and it also went to the GEM. The signal to the PSOM came through the GEM (I assume the GEM did the conversion and that converted signal went to PSOM but it doesn't matter since I don't have or need a PSOM). Regardless, the PCM got the signal directly from the dss/vss, in which case the PCM converted the vss/dss signal to use it and the GEM/PSOM got the raw signal.
I am going to see if I can take my dss signal source and piggyback it on its way to RABS module on my '89 F-150 and run that directly to a '97-'98 PCM as raw vss signal. i.e., It looks to me like the vss from the '98 transfer case sender and the dss at the rear diff produce the same raw speed signal data. The raw AC voltage data sent out from ALL of the speed sensors from '89-'98 should be 0 vAC @ 0 mph, and 3.5 vAC @ 30 mph; and at frequency 0 Hz @ 0 mph, and 125 Hz @ 55 mph.
I would need to update the dss sensor at the rear axle of my '89 to use as '92-'98 input data because '89-'91 signal had resistance range of only 190-250 ohms; whereas '92-'98 was 1300-1550 ohm range. The RABS signal that my '89 might then be off with an updated sensor but I don't see why I can't just use the '98 vss signal from my transfer case ('98 donor) anyway. What I do with that raw signal is either run it directly to a PCM vintage that expects to see an AC signal or through a PSOM then to a PCM vintage that expects to see a DC digital signal (even though I don't need the rest of the PSOM outputs for my '89 chassis).
On the F-150's in '97-'98 the dss/vss signal can be found on pin #58 on the PCM connector and at pin #18 on the GEM connector. These pin numbers are not the same as they were on the '92-'96 F-150's.
I will need to compare factory wiring schematics for Explorer vs F-150 to confirm.
In my view it seems that a raw AC dss signal at rear axle is going to be the same signal as the vss raw AC signal from the A/T in any '92-'98. Either sensor could provide the AC data source. If so, that would make swapping in a late model 5.0L or 5.8L complete engine/EFI into an older vehicle chassis (and use whatever trans you want). As long as you can get a dss signal; it can serve as the vss signal to the new engine management electronics.
True?
For the F-150 anyway '92 was the introduction of the PSOM + RABS. The speed signal (vss/dss) went through the PSOM and RABS modules prior to going to the PCM and Cruise control modules. From '97-'98 the vss raw signal went separately (but the same unconverted signal) to the PCM; and it also went to the GEM. The signal to the PSOM came through the GEM (I assume the GEM did the conversion and that converted signal went to PSOM but it doesn't matter since I don't have or need a PSOM). Regardless, the PCM got the signal directly from the dss/vss, in which case the PCM converted the vss/dss signal to use it and the GEM/PSOM got the raw signal.
I am going to see if I can take my dss signal source and piggyback it on its way to RABS module on my '89 F-150 and run that directly to a '97-'98 PCM as raw vss signal. i.e., It looks to me like the vss from the '98 transfer case sender and the dss at the rear diff produce the same raw speed signal data. The raw AC voltage data sent out from ALL of the speed sensors from '89-'98 should be 0 vAC @ 0 mph, and 3.5 vAC @ 30 mph; and at frequency 0 Hz @ 0 mph, and 125 Hz @ 55 mph.
I would need to update the dss sensor at the rear axle of my '89 to use as '92-'98 input data because '89-'91 signal had resistance range of only 190-250 ohms; whereas '92-'98 was 1300-1550 ohm range. The RABS signal that my '89 might then be off with an updated sensor but I don't see why I can't just use the '98 vss signal from my transfer case ('98 donor) anyway. What I do with that raw signal is either run it directly to a PCM vintage that expects to see an AC signal or through a PSOM then to a PCM vintage that expects to see a DC digital signal (even though I don't need the rest of the PSOM outputs for my '89 chassis).
On the F-150's in '97-'98 the dss/vss signal can be found on pin #58 on the PCM connector and at pin #18 on the GEM connector. These pin numbers are not the same as they were on the '92-'96 F-150's.
I will need to compare factory wiring schematics for Explorer vs F-150 to confirm.
In my view it seems that a raw AC dss signal at rear axle is going to be the same signal as the vss raw AC signal from the A/T in any '92-'98. Either sensor could provide the AC data source. If so, that would make swapping in a late model 5.0L or 5.8L complete engine/EFI into an older vehicle chassis (and use whatever trans you want). As long as you can get a dss signal; it can serve as the vss signal to the new engine management electronics.
True?
