1992 F150 4x4 5.8L, truck ran fine, going to get steps put on. Followed up by getting the SMOG check. Leaving the Smog check, I noticed as I drove onto the freeway, that the Speedometer was not working (and the electronic odometer, was blank), then I also noticed the radio was not lit up, and the automatic transmission was shifting really hard. The A/C was not working, and it had been working before, too.

Since the guy that installed the steps is a good friend, I went back to his shop. We checked all the fuses, because some of these things are controlled by fuses(?) maybe. All of the fuses seemed to be OK. Pulling fuse # 8 had some sparks flying. It turned out that it may be the problem, because the speedometer memory is a part of that circuit. The dome light is a part of it (and it doesn't work), so I unscrewed the dome light, and pulled it off the ceiling of the cab. The fuse doesn't make sparks now, so the dome light is definitely a part of the problem, but the Speedometer and Odometer do not work, the A/C doesn't work, the radio doesn't work, and the transmission shifts very hard, still.

I would like for somebody to help me analyze what the indicators are telling me. I can't read numbers on the Odometer, so it is impossible for me to get any fault codes to interpret.

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When he put the steps in did he drill through the wires in the rocker panel. Just a thought.

 

Yeah, that's what I was thinking too. It's easy to drill through one side and forget about what may be just past your view...

 

The speedometer information (VSS) comes from an exciter ring next to the ring gear in the rear differential. This information goes to the PSOM and the PSOM sends data to the speedometer, odometer, and the PCM. The PCM uses this data to shift the Transmission. Transmission will shift hard without this data.

The PSOM is powered by fuse 8 (15A Hot at all times) and fuse 18 (10A Hot in Run).
Fuse 8 also powers Courtesy Lamps, Engine Compartment Lamp, Power Mirrors, Vanity Mirrors, Speedometer Memory, Warning Chime and Keyless Entry
Fuse 18 also powers Speedometer, Electronic Shift Control, Air Bag Diagnostic Monitor, Day/Night Mirror and Shift Lock.

 

Thanks! I may not be able to get time to look for the wires in the rocker panel, before next Monday (I can drive my car), but I might be able to pull the steps off. If the screws only cut insulation, with the screws out, everything just might work. If the screws cut the wires, then I have another problem!

This truck doesn't have Air Bags, and some of the other things, so Air Bag Diagnostic Monitor, Day/Night Mirror Power Mirrors, Vanity Mirrors, and Keyless Entry don't apply. The rest of the items certainly do, though!

I'll report back when I get the steps off, THANKS AGAIN!

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The diag codes would not show on the odometer on that truck anyway, the would be flashed out with the check engine light.

 

i had this happen to me, exact same problem! all i had to do was replace a Bad fuse... check it out!

 

THANKS TO ALL!!!

I pulled the drivers' door threshhold plastic trim up and, LO AND BEHOLD, right there in front of me were the top mounting screws for the new step. Sure enough the front most one went dead center through the wire bundle, and the rear one was tight over the top of the wire bundle. We pulled the screws out, and checked the Odometer, and nothing, so we cut the wire bundle wrap loose for a ways beyond the screws, and sure enough some of the bared wires had hard contact with each other. We separated the wires, replaced the blown fuse, tried the key on and the Odometer lit up and showed the mileage. I temporarily taped the wires individually and then wrapped them with electrical tape.

Started the truck and Odometer came on, and so did the rest of the stuff, radio and . . . The A/C is not working, but that is another problem now since everything else is. The A/C clutch does not activate, for now, but I will deal with that another time.

Drove home and the speedometer worked as expected, and shifting is back to normal.

THANKS AGAIN!!

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I had this happen to me once, a long time ago. But it was a wire that ran over the steering wheel . take off cover of steering wheel and if I remember right they sit right on top,they rubbed thru.shrinked wrapped and has been fine.

 

If only all the problems would be this easy to fix !!