Odd E4OD issue towing

[chillman88]

Hey guys,

@saburai is hauling from Virginia back to Florida and having issues kicking into limp mode. He gave me a call because he's driving and asked me to post on here.

Driving along and at higher speeds his speedometer is giving him issues, can't remember exactly what he said it was doing, I'll have to call him back but it's drifting or something.

Regardless it runs fine, but when the speedometer starts acting up it will kick into limp mode and flash the OD light. He's tried changing the VSS multiple times.

What's odd is if he leaves his code reader plugged in the light stays off and it works fine. He's curious if just leaving the code reader plugged in is going to cause any issues with the solenoids or burn anything up. He said transmission temp is fine and holding steady around 190 I think he said.

Doesn't make any sense that it works fine with the code reader plugged in but it does.

 

[BeastMaster]

Your speedometer MUST be working properly. The E4OD requires a clean VSS signal from the PSOM, which is part of the speedometer circuit board, mounted directly behind the speedometer in the dash.

Check everything in the VSS circuit. Filings on the VSS sensor...ABS acting up too? If so, dead giveaway...

I battled this demon off and on for.two years. It took a battery powered oscilloscope on the PSOM output to nail this one for me.

 

[yARIC008]

If i'm not mistaken, i think there are voltage regulators that can begin to fail on the PSOM which would probably cause this. The problem is in the dash.

 

[Greenie]

It might be as simple as the speed sensor in the differential having filings on it. Try removing the sensor, cleaning off the surface and reinstalling it. Happens to mine now and then.

 

[chillman88]

If i'm not mistaken, i think there are voltage regulators that can begin to fail on the PSOM which would probably cause this. The problem is in the dash.

That's what we're thinking. VSS has been replaced multiple times and there were no filings on it.

 

[Thewespaul]

Psom, regulator or dash ground. No stored codes?

 

[chillman88]

Psom, regulator or dash ground. No stored codes?

That's a question he will have to answer. His primary concern was, since the issue doesn't come up with the code reader connected, will any harm come from leaving it like that for this trip. I know he's been fighting this on and off since last fall when he left NY for Florida, and has had a couple threads about it as well.

 

[trackspeeder]

The tranny isn't running hot or or shifting weird, leave the code reader plugged in. It will be fine.
Take care of the PSOM issue ASAP. The code reader is acting as a band aid right now.

 

[chillman88]

The tranny isn't running hot or or shifting weird, leave the code reader plugged in. It will be fine.
Take care of the PSOM issue ASAP. The code reader is acting as a band aid right now.

That's what we were thinking. Thank you!

 

[saburai]

Hi Gents! Thank you Chris, and the rest of you guys are great too! I had some unrelated issues, I had to swap the tow bar and rent a U-Haul tow dolly, then I ran into some construction and such, so I didn't get in until around 7:30 a.m. yesterday. I took a shower, hung around the house and then went to sleep. I slept like a dead man until this morning. I'm pretty stiff and sore today so I'm just going to return the U-Haul and clean out the truck and recuperate for a day. Wes, yes, it did throw two codes. I didn't bother looking them up but I did write them down. I'll find the scrap of paper when I clean out Raylan. But I'm reasonably certain that it is the same codes that it always throws. Converter lockup and I don't remember. However based on what I know, the converter lock-up code comes from a discrepancy in engine RPM and miles per hour. Speedometer error increases with speed so based on past experience, the transmission is fine. I'm thinking that I would like to replace the dash module as well as the p s o m. Do any of you guys have either or both? Wes, might you have what I need and where does the dash ground? I'll need to check that. Please let me know and if I didn't say it before you guys are great and this place rocks! Does Rock Auto or any other supplier stock the parts?

 

[saburai]

Psom, regulator or dash ground. No stored codes?

Codes 65 and 74

VSS and BOO respectively. BOO is only because I didn't do the full test. I'm reasonably certain that the speed sensor is fine...
Would you happen to have a PSOM and/or the dash module?