nelstomlinson
Full Access Member
I'm having an intermittent problem with the shifter: three times now the transmission has downshifted to 1st, while moving. The speed display shows 0, while the truck speedometer still shows the correct speed. This happened once in 4th at about 45mph, twice in 2nd at low speeds. Each time, stopping, putting it in park then starting up again has restored things to proper functioning.
After the second instance I replaced the vehicle speed sensor, and checked the wires running to it, but the problem recurred.
I asked US Shift for troubleshooting suggestions, and they replied:
I tapped into the wire running into the back of the speedometer, which I believe runs from the PSOM? or is the PSOM the speedometer? I'm finding places that repair the PSOM, and all of them seem to be talking about repairing the speedometer, not the device which sends a signal to it.
My speedometer needle doesn't waver or drop out, which is what I always associated with a failing module.
Anyone have any ideas for differentiating between PSOM (whatever that is) and something else?
After the second instance I replaced the vehicle speed sensor, and checked the wires running to it, but the problem recurred.
I asked US Shift for troubleshooting suggestions, and they replied:
It depends on how exactly you have the TSS harness connected. Are you using the single wire PSOM method as shown in our manual, or are you connected directly to the rear axle ABS speed sensor?
Either way, it sounds like an intermittent wiring problem. If you are connected to the PSOM, the module may be failing. PSOMs are known to fail especially given their age, and there are a few companies that specialize in refurbishing them.
I tapped into the wire running into the back of the speedometer, which I believe runs from the PSOM? or is the PSOM the speedometer? I'm finding places that repair the PSOM, and all of them seem to be talking about repairing the speedometer, not the device which sends a signal to it.
My speedometer needle doesn't waver or drop out, which is what I always associated with a failing module.
Anyone have any ideas for differentiating between PSOM (whatever that is) and something else?