Long story short I’ve been chasing transmission problems even after I put a new one in my truck. It’s a 97 7.3 with the e4od 2wd and I’ve finally narrowed it down to the speed sensor. The truck is throwing a p0500 which is VSS fault and it keeps throwing the transmission into limp mode slamming gears. I’ve replaced the sensor itself, the tone ring inside the rear end, and the pigtail that plugs into the sensor. I haven’t pulled the full wiring harness out completely yet because it’s a hassle and runs clear up to the front of the truck and mines a 4 door long bed dually but from the several areas I have pulled down the wires look great they’re still wrapped in loom and protected. I was told the wires run into the gauge cluster into the psom on the back of the speedometer but I haven’t looked. I’ve also seen other people say the wires branch off into other areas. I’m just not sure where to go at this point and any help would be appreciated. There’s no consistencies in it failing either. Some days I could drive all day long and not have a problem and some days it’ll just go into limp mode. I’ve even driven it to a McDonald’s just fine without shutting it off and when I pull out of the drive thru it won’t shift. It’s completely random and is starting to happen at least once daily

 

Sounds like it could be a cluster problem.

1. While the symptom is occurring, monitor the AC volts at the rear of the cluster, indicating Differential Speed Sensor input is OK across the Red/Pink (RD/PK) and Light Green/Black (LG/BK) wires.

2. If present, monitor the Programmable Speedometer Odometer Module (PSOM) output frequency on the Grey/Black (GY/BK) wire.

3. If loss of this signal occurs as the symptom does, replace the faulty PSOM. Tech Tips: Typical PSOM frequency readings would be about 25 Hertz at 10 MPH and increase 20 Hertz for each 10 MPH increase in speed.

 

I have been going through this for a while now . Out of the blue . Rebuilt trans with few miles on it I have little problem in the morning , almost every day after work I have to stop & restart the truck . I finally broke down and changed the VSS to an old " good" ford one from 06 I had on the shelf . All good for a while . Then it started all over again. SO I eventually put in the only brand I could get & changed the pigtail because the clips were broken ( from 06) . All good again . For a while ......It started again.

So I hooked my scanner to the truck & it showed zero on the speed sensor while moving . When I got home I paused & read the trans codes . there were too many to read them all . Most un identifiable by number . I cleared them to start over and have not had an issue since . My thought was the PCM was overwhelmed from the prior crap . I am also thinking about replacing the TDE1 with a new one for S&G . Given that every time I did something to it , it improved , I still am not convinced that it is fixed . The scanner speeds & the speedometer speeds do not match . The PCM is higher by 10 MPH . Scanner shows one code, but it is related to my EBPS.

At one time I thought it may be related to the TPS . No proof on that yet .

I went down this road in 06 when I got the truck . Had a broken wire to the VSS . But back then , the speedo & ODO stopped working every time I hit a bump in the road . . Once I fixed the wire , the problem never returned till this spring .

At the time ford said it was the VSS. Thats why I had a good one on the shelf , next they said it was the PSOM so I bought a new cluster . Its still on the shelf but the miles are closer to actual now . (PO already replaced it trying to fix the trans ) . So I have no idea how many miles are on the truck .

 

I don’t have a scanner good enough to read all that unless I just don’t know how to use it which is a possibility. The only transmission code it keeps throwing is for the speed sensor but I clear it every time and it just comes back. I’m thinking the PSOM is my problem as well but I need to run some tests to be sure. These trucks are known for electrical issues and it’s driving me crazy but at least I’m not the only one lol. Hope your problem doesn’t come back

 

how would I monitor these while driving it? Just pull the cluster out and let the speedo hang or can it be done with some kind of scanner

 

might need a helper to hold the meter to those points while driving or run a jumper wire to passenger seat

or block rear end up and spin tire by hand while you measure it

 

so update. I just drove the truck and it wasn’t wanting to shift so out of curiosity I started tapping on the speedometer pretty hard and what do you know it started shifting fine. Might be a coincidence but I did that 2 or 3 times on my way home and each time I tapped it fixed it

 

May only be a loose connection .

 

One way to test is to put the rear end on Jack stands, simulates driving but safer while jiggling wires. . I didn’t have shifting issues because, 5 speed. But sometimes banging on it brought it back to life.
Probably the PSOM . Modulemechanics.com did a nice job fixing mine.

 

Its been a few days since I plugged in the scanner & cleared the codes . The scanner seems to agree with the speedometer a lot closer . No Idea whats happening but without touching anything the trans has been working fine . That said , we shall see .............

 

Until today .

 

me too lol. Saturday night I pulled the batteries made sure they had a good charge and cleaned the corrosion from the terminals then drove it an hour and an hour back home on Sunday and all was fine. Also pulling the batteries let the computer reset. Drove it to work this morning just fine and on the way home the trans started acting up again. I pulled off and hooked up my scanner. 61 codes came up saying basically everything failed in my truck. Large fuel leak, low fuel pressure, turbo boost loss, bank 1 this, bank 2 that. Everything you could imagine failed but the truck still runs perfectly fine so I have no idea what the deal is

 

Check the wiring behind the cluster, I had my OBS shift cable bracket rub thru the harness and making my pedal non function and OD light to blink, worth a shot checking

 

alright I’ll check it out thanks man

 

THe only codes I had were related to the EBPS .