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Strange Problem With Transmission or Sensor?

kcraptor82

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1998 Ford Ranger XLT 3.0L V6 (4R44E Auto)
Do apologize for the long post, but want to explain everything that has been done so far. So picked up this little pickup recently and have been trying to figure out how to fix it. Body was in pretty good shape and only had 103,203 miles on it when I bought it. Now I know it was going to need some work, but I picked it up cheap! So brought it home and started to look into what was wrong with it. So far what I have found wrong with it:

1. Check Engine Light On
2. ABS Light On
3. Airbag Light Flashing & Stays On
4. Auto Trans Shifting Harder Than It Should
5. Exhaust Needs Replaced
6. AC / Heat Blows Thru Defrost Only

First repair was the exhaust. Drove it to a local shop nearby my house and got the muffler replaced and now truck sounds great. Brought It home and started to pull codes. Airbag was showing a code of 27. Just need to fix the Airbag light on the Passenger Airbag Disable Module. Then pulled the OBD II reader out and got these codes:

P0301 Cylinder 1 Misfire Detected
Alright I knew this might happen since the owner told me it had low compression on cylinder one. These engines have a nasty habit of having crap heads and the valves will recess sometimes. So no big deal, will buy new heads and replace them, engine shall run great afterwards! Went and bought two new heads, gaskets, thermostat, etc! Just got to install them now!

C1234 Wheel Speed Right Front Input Signal Missing
ABS Sensor on front right wheel was not working at all. Bought new sensor with harness and replaced it. Cleared codes and ABS light has not returned.

C1102 Acceleration Switch Circuit Malfunction
ABS Sensor on the center of rear differential. Bought new one and replaced. Cleared codes and ABS light has not returned.

Repairs Done So Far:
Replaced ABS Sensors and cleared codes. Also found out someone had replaced the vacuum assisted hubs with manual locking ones. This was causing a vacuum leak and the AC / Heat was stuck blowing thru the defrost. Bypassed the vacuum module that sends the vacuum to the hubs and now the AC / Heat blows thru the vents like it should. Like mentioned before, I replaced the trouble ABS sensors and so far the light has not returned. The miss-fire will be fixed after I of course replace the heads. Muffler was replaced and Airbag light figured out.

The Strange Part:
So before I did any repairs on this truck, the speedometer & cruise control worked! The reason I mention this is because I have read a lot of posts saying if that ABS speed sensor goes bad, then usually these functions don’t work or they act up. Now I have replaced this sensor, but the transmission is still shifting harder than I would like. So I took it to a couple transmission shops that are local and the first shop just wanted to rebuild it, of course. The second shop was more honest and pulled what codes they could and told me it was the Vehicle Speed Sensor fault. Paperwork showed this:

Recommended Repair: CK output speed sensor (-0- Reading)
Codes: P301 Cylinder 1 Miss-Fire, P1808 4WD indicator, P1804 4WD High Indicator, 3 B Codes, P0500 Vehicle Speed Sensor Fault

Mechanic onsite told me that he wasn’t getting any reading out of the speed sensor. Now they told me there should be one on the side of the transmission or transfer case. This sensor would cause the transmission to shift harder. That made sense to me and I brought it home. I started looking for this sensor on the side of the transmission and found nothing of course. From research, seems this model doesn’t have a VSS sensor and the ABS sensor in the rear differential plays a dual role.

So what I would like to know:
Now since I replaced this sensor and still having the same issues, plus the speedo and cruise control works, WTF? Could I have bad wiring and need to tone the wires to see if there is a break somewhere? But even if I had bad wiring, then how the hell is the other components working? In theory, I shouldn’t have a working speedo and cruise, etc. I am scratching my head over this because none of my problems match what others have dealt with? Any suggestions?
 

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Transmission shifts hard when computer has gone into LIMP mode. If CEL still present, likely in limp mode. Replace camshaft synchronizer and sensor with Motorcraft in case it hasn't been. Only plugs this engine really likes are Motorcraft platinum. Clean MAF and entire intake before changing plugs.
 

bradberry

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I have a 1998 3.0 4wd and I replaced the VSS on the rear dif. It did not fix my issue either so I bought the new wire harness for the VSS. That should fix it but I tore my Achilles Tendon so I have not had a chance to replace it.
My rig was doing the same thing except the ABS light never came on.

Sent from my SM-G920V using Tapatalk
 
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94RoadkillRanger

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'94
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From the trans (vehicle speed sensor) to the PCM, cruise control, and speedometer there is a grey/black wire that may have damage. Possibly there is either a break or short in this electrical connection that is intermittent. It may or may not be the vehicle speed sensor (also). When it rains hard on my '98 3.0 w/automatic my trans acts up with hard shifting because I have a water leak. I just haven't bothered to fix it yet, too many other things going on. I'm on page 64-2 of the "Electrical Vacuum and Troubleshooting Manual".
 

RonD

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1998 to 2000 Ranger did use the rear axle ABS sensor for speedometer, cruise and computer(trans shifting)
The P0500 code means computer only is not getting the speed signal, computer can't tell if speedo or cruise is working or not, it just knows it is not getting the speed signal.

The VSS on rear axle has two wires and both run to ABS module directly.
In behind the Radio is the GEM(generic electronic module) it runs all the electrics in the cab, i.e. when you turn on the wipers you are actually sending the "turn on wipers" command from the wiper switch to the GEM, GEM then activates the wiper relay

Ford decided to use the GEM in 1998 Rangers as the true speed interface, rear axle VSS probably has about 12,000 to 14,000PPM(pulses per mile), Ford speedos are setup for 8,000PPM so an interface was needed to correct for true speed.
So the two VSS wire were spliced and connected to GEM
GEM is programmed with tire size at the factory, it then converts the ABS VSS pulses down to the 8,000ppm using the tire size for fine tuning.
It then sends out the True Speed signal on 1 wire to the computer, speedo and cruise.

The VSS outputs an AC voltage, so a sine wave above and below 0volts, only the above 0 voltage pulse is needed, the + side of the wave.
So one wires coming from the VSS is Grounded, the other wire is the signal wire.
Since computer, speedo and cruise are alreadying Grounded, they only need the 1 GEM "signal" wire.

Since Speedo and Cruise both work, then either Computers speed wire is broken or computer is.

On the Rangers Ford uses a Grey/Black striped wire from GEM to computer, speedo, and cruise
On the computers connector it is on pin 58, 1998 3.0l Ranger
Computer connector should be on the firewall up high towards passenger side
Disconnect battery and remove this connector, check it for corrosion
 
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