5r55s Output Shaft Sensor?

ixtlan

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Problem:
Speedo intermittently reads high (10-20mph) but then after a shutdown may return to normal.
Generally on start, it will be at zero mph and follow speed as normal. But at times on start it may be at 10mph parked and follow 10 over and back consistently with speed increase and slowdown.
I am thinking it is the Output Shaft Sensor...????
But what is the part number on the OSS sensor?
Cant find anything that tells me the Ford P/n or conclusive diagrams that say it is Motorcraft p/n or anything consistant.
Anyone got a trany out that can read the p/n?
Or know for sure what it is?
2005 5R55S
 

Pentalab

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You can also read the speed on the OBD port. I do that once in a while with my aeroforce gauges plugged into the OBD port. This is on my 2010 automatic, same 5r55s. I had a similar problem to yours on my old 96 Ford escort. That was a mech cable setup, which was a bitch to get at...to screw back in tightly. Speedo would jump up 10 mph, then wander back down.... but only on the hwy .

You should be able to get the pn for the OSS sensor from any ford dealer, or any tranny place that services a 5r55s. I have no clue where the OSS sensor is even located on the 5r55s.
 

redfirepearlgt

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Datalog the mph using your programmer device. I am assuming you have one since you have a gear swap higher than 3.73. This would be better than just throwing parts at it. The clusters have been known to have problems over time. There are rebuild kits available to the servo's as I recall.
 

ixtlan

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I do need to verify that the feed is unstable. Then that would clinch the sensor as the problem.
I will do that when I get a chance. But still if it is bad I need to get the p/n.
 

07 Boss

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I would think possibly stepper motor in the speedo. I could be wrong but if the output speed signal was hinky I would think it would throw a tranny code or blinking CEL.
 

ixtlan

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The Stepper was changed before and I did change it again thinking that myself. But no fix this time.
The speedo is smooth and follows well, it just starts in the wrong place now and then.
But then it will fix itself on a shutdown and sometimes not till another shutdown.
Makes it hard to troubleshoot....
I need to haul around my data reader and catch it when it goes squirrely and see what it reads.
And before anyone asks the needle is tight and not the problem. lol
No CEL no nothing. I'm sort of fearing it is some chip on the dash circuit board but don't want to give in on that yet.
 

redfirepearlgt

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Intermittent ghost faults are never any fun. I deal with them all the time art work. If you had an Aeroforce gauge you could set it to monitor MPH at all times. The more I see these types of problems cropping up the more I find myself thinking about picking up one of those gauges. I looked to see if canbus communications uses a shield drain to maintain databus integrity but it is apparently robust enough not to need a shield, just a twisted pair according to the prints I have access to. Only the crank trigger and a few other devices have a shield to drain any induced noise that could cause false data or feedback.
 

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