99 4 Cyl Automatic No Speedometer

[Captain Bravo]

Hey guys. I am trying to help out a single mom that my wife works with. She has a 99 Ranger 4 cylinder automatic.

When I first checked it out it had a broken spring shackle, erratic throttle position sensor reading, occasional stalling at stops, no speedometer, and the transmission was shifting erratically.

I changed the spring perch and shackle, tps, and vss. It now drives better, but the transmission isn't shifting quite right (at the right speeds - the shifts are nice and firm with no slippage) but it is shifting better than it was. But the speedometer isn't working. My Torque Pro app and bluetooth adapter will read vss usually but I can't get anything from this truck. Because of that, I don't think it is the speedometer itself. I tested the wiring from the sensor to where the harness goes into the truck itself and it is all fine. Any ideas of where to go from here?

Thanks, and sorry for the long first post.

 

[Earl43P]

Welcome to The Ranger Station!

If you send me a Private Message and include an e-mail address, i'll send you schematics.

The VSS feeds into the GEM for that truck.
The GEM conditions the raw VSS signal for use by the speedometer, RABS and PCM.

Pages 42-2, 59-1, 64-2 when you get the file.

 

[Captain Bravo]

PM sent. Thanks a lot.

 

[Earl43P]

Just following up on whether you had a chance to get back on this?

Curious to know what you find.

 

[Captain Bravo]

I didn't have as much time to work on it as I was hoping, but I have verified that there is a good signal being generated by the sensor, and that the plug under the drivers seat is not the problem. My plan this evening is to move up to the gems unit and verify the input and output there.

I definitely plan to post my findings. Hopefully help the next guy find a similar problem a little easier.

 

[Captain Bravo]

OK, I was reading up on the GEM unit while waiting for/eating supper. Read one site that said they pulled fuse #25 and reset the GEM unit and their problem disappeared. So just for kicks I tried the wipers when I went out to work on the truck (I read that the GEM controlled the wipers) and they didn't work. I pulled fuse 25 and put it back in and they worked for a minute or so. So, I started the truck, put it in drive, and turned on the wipers. At this point the wipers and the speedometer are not working. I pulled and replaced fuse 25. The wipers came on and the speedometer jumped up to about 11mph. Lightly stepped on the gas, and the wipers and the speedometer quit. Does that mean that the GEM is bad or is there something specific that might cause the GEM to do that?

 

[Captain Bravo]

For the benefit of anyone searching with this same issue, the problem in this case was the ground strap running from the cylinder head to the wiper motor. The end on the cylinder head had corroded completely off. I ran a new wire and the speedometer and wipers are operating correctly, and the transmission is shifting as it should.

Many thanks to The Ranger Station and Earl43P for the help.