I am taking the family camping this weekend and ran into the dreaded flashing overdrive light.

Our route was Greenville SC to Boone NC and this occurred shortly after going up the steep grade on 321 into Blowing Rock.
I was towing our bumper pull toy hauler which weighs approx 9,000 lbs.
Coming up the grade the fog was thick and dense and visibility was extremely poor.

I pulled over as soon as I could and checked transmission fluid levels before shutting off the truck.
I’ve been running Mobil 1 synthetic ATF and it looked and smelled brand new, level was correct on the dipstick for H range.
My transmission temp never exceeded 160º F and the truck was running and shifting fine.

I have a brand new BTS E4OD installed back in Feb 2021 with less than 10k miles on it.
I run the big Mishimoto 37 row 6.0 cooler and transmission temps have never exceeded 180º
I installed brand new hard and soft lines along with the BTS trans and cooler at the same time.

I have an OBDLink MX+ bluetooth adapter and am familiar with FORScan Lite on iOS.
I had brought along a Windows laptop and tried to read codes using FORScan on Windows but it did not show anything under DTC?
We were only 30 minutes from our camping destination and I do not like setting up in the dark so I decided to continue.
The truck drove and shifted fine the remainder of the drive however the OD light continued flashing.

Tonight I attempted to read codes again using FORScan iOS and at first it returned hundreds of codes.
I don’t know if this is a FORScan bug, or something is up with my PCM?
We effectively drove through the clouds so I’m wondering if some connections got saturated with moisture.
After several attempts I got a successful looking result which I will attach below.

My next steps are to try clearing codes and drive around town unloaded (no towing) to see if any codes return.
I also plan to put a call in to Brian at BTS for any advice.
I do not suspect anything simple like the VSS because my speedometer worked flawlessly.
I believe the P0238, P0478, and P0236 codes were preexisting due to high boost from running around town with my S364.5
The P007D, P007C, and P0001 are new to me, but the P1728 seems like the important one here.

 

I have been studying other P1728 threads and am going to take a hard look at my brake lights tomorrow.
On theory is that perhaps moisture from the thick fog and rain was shorting out that circuit telling the torque converter to unlock?

The interesting thing was that the flashing overdrive light resumed immediately after restarting the truck while it was still in park.
But perhaps this was just the truck telling me there is a stored code that needs to be looked at.

I will update tomorrow after resetting codes and test driving unhitched around town.

 

I cannot offer any advice for the E4OD or flashing OD light. Although, if you are still experiencing problems and need a hand getting the trailer home, I am in Hartwell and can come up to move the trailer for you with my truck.

We towed a 32 ft travel trailer from GA to Seattle WA and back and all around the southeast, so I am familiar with how they travel.

You have my number.

 

Check your trailer wiring, if somehow moisture got inside the plug its shorting out allowing for the TC to slip, I've had this happen to me on my OBS on those record rain storms, the trailer plug was dangling and it got full of water shorting out and making my TC to never lock up.

 

Following along.

 

Thanks for the generous offer and thoughtful replies! I spoke with Brian this morning and we agreed it is probably a small electrical gremlin possibly related to water entry at the 3rd brake light?

This morning I cleared the codes and have been driving around town unhitched with no issues. It is still raining and 96% humidity but the flashing OD light has not returned

When the weather clears I am going to inspect the brake lights, trailer connection, and other electrical harnesses. Thanks for following along, will report back soon.

 

Good news!

I don't know about the Greenville and Boone areas, but here in Hartwell it has been raining heavy off and on for the past 5 days. It doesn't surprise me that you described your trip into the mountains as driving into the clouds. My offer still stands if you need help, just let me know.

Other than that, Kate and I are looking forward to seeing you guys at the GTG and Jackrabbit Mountain NP in a couple of weeks.

 

Great to learn what might go wrong that hasn't yet.
Please send ALL of that rain to California.

 

Had a busy weekend with the kids and did not have time to dive into much troubleshooting. The truck ran fine unloaded around town on Fri & Sat with no new codes. Today the weather finally cleared and was warm and sunny. Made the return trip home with no issues!

I still plan to investigate further, I know for certain the 3rd brake light is poorly designed and water enters there. My plan is to pull everything out, clean and perhaps dialectic grease on any connections and then some type of gasket or sealant to prevent future water intrusion.

Overall I am still very confident in the truck. It is a great feeling knowing all you FTE’ers are on hand to contribute advice and having Brian from BTS to back me up too! I have another towing trip next weekend and will put things to the test again. I will post again here after I have time to dig deeper into potential problem areas.

 

Good to hear things went well on the return home trip. If you have some butyl tape laying around for use on the camper, that might work as a sealant between the light housing and the cab. We carry some with us for "just in case" moments.

Some dielectric grease is always a good idea too.

See you on the 22nd at the campground.

 

Just a quick update, finished a 550 mile round trip to the mountains this weekend without any problems. Truck ran great and the transmission was flawless. Still haven’t had time to properly seal brake but will try to post pics when I do.

 

The story continues.. yesterday while towing up the steep twisty section of US-76 between Clayton and Hiawassee my overdrive light started flashing again and the truck threw another P1728 Transmission Slip Fault.

This time the weather was warm and dry, so I have no reason to suspect moisture problems. Interestingly, the truck towed over 500 miles last weekend with no problems. The only difference was interstate roads (less twists and turns).

I need to do more reading about P1728 to understand exactly what causes that code. The truck continued to tow and shift fine, so I suspect it is something electrical or possibly related to my driving behavior. Should make for interesting discussion at the get together today.

 

The PCM calculates an output shaft speed from the VSS (Vehicle Speed Sensor) on the rear axle. In fourth gear with the torque converter locked it compares engine speed to the calculated speed. With the converter locked there should be essentially no difference. If the difference is above 50 RPM for a certain amount of time it sets this code.

 

Thank you Mark, that is very helpful to understand! I appreciate you sharing your first hand knowledge about these transmissions.

I was able to reproduce the P1728 again on the drive home and this time also got P0344 Camshaft Position Sensor A Circuit Intermittent and P0238 Turbo Charger Boost Sensor A Circuit High Input. This occurred when I was passing a slow moving vehicle on steep uphill twisty mountain road, and I was using a healthy amount of accelerator pedal (but not flooring it).

The P0238 doesn’t surprise me as my T4 setup is making well over 30 psi and I’m sure the factory MAP sensor can’t handle that range.
The P0344 is interesting and may be the root cause of the P1728, if the PCM is seeing a fluctuating or intermittent RPM while calculating output shaft speed.
I will focus on my CPS wiring and perhaps try the spare OEM Motorcraft CPS I have waiting in the glove box.

The interesting thing about my circumstance is that I had overdrive turned off, that would be 3rd gear, right?
I understand that the torque converter may lock during 3rd, so I suppose the PCM might still be doing that calculation regardless of gear selection.

 

Dmco, like I mentioned this weekend at the north GA GTG when speaking to you about the O/D light blinking, I looked into the service manual for anything that may help you out. Although, the manual I have is for the 1999 - 2003 7.3L with a ZF6 or 4R100. The DTC P1728 stated the following "Refer to the powertrain group in the Workshop Manual for diagnostic procedures."

Again, this would be for the 4R100, so I will not attach the procedure in PDF format.

Going forward, I think between your knowledge and ability with the help of Mark K and Brian at BTS, you are in good hands. Keep us updated sir.