5R110 HELP
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FTE Chapter Leader
Joined: Feb 2004
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From: Wayland, MI
5R110 HELP
I am getting an intermittent P0791 code. It is the intermediate shaft speed sensor (?). The issue is it doesn't come on all the time. Is this going to be a solenoid failing? When the light is on the truck doesn't go into 1st gear at a stop, but it will shift smoothly all the way to 5th and the torque converter will lock in the way it is supposed to. I have a few friend that are transmission guys and the are stumped. Could it be a wire harness, or could it be a soleniod, or could it be the TCM?
When I take it to the dealership they can't seem to find it, mainly due to the light not flashing.
Anybody have any ideas? I would really like to get this to stop flashing.
Thanks in advance for any thoughts. Lets hear what your ideas could be....
When I take it to the dealership they can't seem to find it, mainly due to the light not flashing.
Anybody have any ideas? I would really like to get this to stop flashing.
Thanks in advance for any thoughts. Lets hear what your ideas could be....
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,730
Likes: 2,658
From: SE Florida
A solenoid can't cause a speed sensor code. It could be the speed sensor, but is most likely an intermittent open in the wiring between the PCM and the output speed sensor.
I've also seen codes like this from a defective alternator. A diode in the alternator fails and the alternator puts an AC signal on top of the +12V DC that it is supposed to output. This AC signal plays havoc with speed sensors.
I've also seen codes like this from a defective alternator. A diode in the alternator fails and the alternator puts an AC signal on top of the +12V DC that it is supposed to output. This AC signal plays havoc with speed sensors.
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FTE Chapter Leader
Joined: Feb 2004
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From: Wayland, MI
the speed sensors have been replaced. I also just put an alterantor on the truck when we were in St Ignace for the car show. I know, great timing for that to go out.
I have messed with the wire harness down by the trans. I have removed and cleaned and doubled cheecked all the pins to make sure they had good contact. I also went ahead and called a dealer to see about the wire harness itself and found that they were nationally back ordered through the end of August (I called about a month ago), I have the harness from the transmission up on order. Is this where you think the wire may have an open?
I have been slowly trying to track this down since last winter. best part is for the last few days it hasn't been flashing and the truck actually feels right again.
Thanks for the help Mark. Let me know if that is the harness you were refering to. I can call and get the part number from my buddy at the Frod dealer to make sure I am getting the harness you are referring to.
Toyman
I have messed with the wire harness down by the trans. I have removed and cleaned and doubled cheecked all the pins to make sure they had good contact. I also went ahead and called a dealer to see about the wire harness itself and found that they were nationally back ordered through the end of August (I called about a month ago), I have the harness from the transmission up on order. Is this where you think the wire may have an open?
I have been slowly trying to track this down since last winter. best part is for the last few days it hasn't been flashing and the truck actually feels right again.
Thanks for the help Mark. Let me know if that is the harness you were refering to. I can call and get the part number from my buddy at the Frod dealer to make sure I am getting the harness you are referring to.
Toyman
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Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,730
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From: SE Florida
The PCM is behind the parking brake pedal. The wiring between there and the transmission could have a wiring problem. I don't know how the harnesses are configured.
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I've seen many "new" rebuilt alternators with bad diodes right out of the box. Quality Control is to spin them and see if they put out some voltage, so don't discount the alternator just because you just installed it.
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FTE Chapter Leader
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From: Wayland, MI
Make sense on the alternator. But for 2 of them to act the exact same way.
I will check the harness behind the park brake lever. Ironically, I notice the issue when I mess around the break lever. When I took out the other tuner the light stopped flashing, and has just started to flash again....2 days later.
At least it might be isolated. I will take the kick panel off tomorrow after work and see what it looks like.
Thanks for the help and the suggestions......keep them coming.
Toyman
I will check the harness behind the park brake lever. Ironically, I notice the issue when I mess around the break lever. When I took out the other tuner the light stopped flashing, and has just started to flash again....2 days later.
At least it might be isolated. I will take the kick panel off tomorrow after work and see what it looks like.
Thanks for the help and the suggestions......keep them coming.
Toyman
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,730
Likes: 2,658
From: SE Florida
How do you know these are good without testing?