Serious problem with my 08 f150 5.4
. Speedometer jumping around and transmission stops pulling or changes gears and goes in fail safe mode
I have changed output speed sensor computer,battery etc
I have also changed battery terminals. I might drive it 100 yrds or 100 miles never know how far I'll get. Several mechanics have called theirselves fixxing the problem but nothing has fixxed it yet. This has been going on since nov 2019. Just spending more money. I dove it 150 miles last week to deer camp. Coming home it took me 9 hours to get back. Any help please.....

 

Did I answer your question in another thread today or yesterday?

I just answered one similar, not sure if it was yours or not.

 

I just put my question on today. Some here having similar problems but mine is a little different.

 

Could be a ground issue. I'm sure there are body grounds someplace for these trucks but I do not know where they are located.

If you can find the body ground, remove the screw, clean it and reconnect. That is about all I have to offer.
If there is a BCM module ground I'd start there.

 

[QUTE=16IngotFX4;6481315]Could be a ground issue. I'm sure there are body grounds someplace for these trucks but I do not know where they are located.

If you can find the body ground, remove the screw, clean it and reconnect. That is about all I have to offer.
If there is a BCM module ground I'd start there.[/QUOTE]
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All the transmission stuff is controlled by the PCM. I'd probably start by checking for any shorted or broken wires between the PCM and the transmission and other sensors.

The OSS sensor wire (DB-YE) goes to PCM connector pin 14.

The TSS sensor wire (DG-WH) goes to PCM connector pin 15.

Since the PCM Signal Return wire (GY-RD) goes to a few sensors (OSS, TSS, Trans Range sensor, Trans Fluid Temp Sensor in the transmission and both downstream O2 sensors), you're going to have to test for any problems between all those sensors at their connectors and PCM connector pin 43.

 

Last night a recommended YouTube video had a similar issue. I'm embarassed to say I watched the whole thing.

After testing like mentioned above, it was determined to be a differential pump (sorry to ruin the end of the movie for you). Different vehicle, not something our trucks have that I know of. But point being, it was a bunch of diagnosis to get to that point. He took us along with the diagnosis process.

 

16IngotFX4, why are you embarrassed? I like his videos. He's very good at what he does and at making the videos. You don't get bored watching.

That reminds me. It was late and I forgot to ask. OP, did you put a scanner on the vehicle to see if it had any stored codes? The trans codes need a scanner that can read the trans codes. Most regular scanners cannot. FORScan is good, free, scan software you load onto your laptop that can read all of the modules. You'll need a specific type of OBDII adapter like the (recommended by FORScan for Windows) to connect the laptop to the car.