Hi folks, got a tough one and looking to see if anyone has had a similar experience or any advice.

We have a 2020 F350 gas (Godzilla motor) truck. Last weekend after driving down from the mountains without any issues, we stopped for gas about 2 miles before getting home. When I started it back up the wrench light and traction control light came on and there were warnings:

1) Hill start assist not available

2) Pre-collision assist not available

3) Service Advancetrac

4) Hill descent control fault

5) See Manual

I stopped in the parking lot, turned it off and back on, and they were still there. Pressed "OK" to clear the warnings (but not the wrench or traction icons), drove home and unpacked some of our camping gear (probably 30 minutes) and then went back out to write down the messages so I could start doing some research and they were gone.

Ever since then, these lights show up intermittently - maybe three times they've shown up in 15 starts of the truck. When they do appear, it is always right after starting the vehicle, never after it has been driving for a while. After pressing "OK" through the warnings, they disappear and don't reappear, but the wrench light and traction control light stay illuminated. These never go away while driving. They do go away if you stop the truck, turn it off, and let it sit for a while (maybe 15 minutes or more). If you start the truck and the lights appear, and turn it off again and then start it again in a short period of time, the lights do not go away. So it seems like there is some kind of "cooling off" period that allows the lights to go off.

When the lights and warnings are on, there is noticeable sluggishness in the acceleration. This happens in low gear when accelerating from a stop sign - you can push the gas pedal to the floor and it just very slowly accelerates and shifts through gears. If you do this while driving on the highway and slow down to say 45, it stays in a high gear like 9 and when you press the gas pedal in to the floor it only very slowly accelerates - there is a long delay and it finally starts downshifting until it gets a little power and then shifts back up. It does eventually make it to highway speeds, so it is not in "limp mode" but something is clearly wrong.

When the lights and warnings are not present, the truck drives fine and there are no known problems and accelerates just fine. If you punch the gas from a stop the engine roars and you get pushed back in your seat. Same thing if you are on the highway and going slower - punch the gas and it immediately drops to 5th, engine roars and you get up and go.

Anyone have any bright ideas or things I should do?

 

I used to get those errors a lot



My fix was the infamous connector by the spare tire mounted to the inside of the pax side frame rail.

this connector is a water magnet and ford does not seal their wire ends like imports do.


fix for me was to disconnect t the connector, spray it inside and out with contact cleaner , then spray dielectric grease on wire and pin side of both the male and female connector. I have not had the error since doing so.

The connector is about 2” wide .

 

This beige one on the bottom, right? Looks ok from the outside but I need to get in to check the connectors from what I've read.

I've struggled to get it apart and trying to avoid forcing it and break it... Seems like it should come apart at the red line and that I should push the tab in the green circle. Is that correct or am I getting this wrong?

 

Yeah push the tab in the green circle, and pull from the left side of the red line. Should come apart, but if it's anything like mine was you will have to motivate it pretty strongly.

 

Original battery? I would get a new one if it is.

 

Some new information. I got the connector apart and didn't see any corrosion. A bunch of dust came out of it, but otherwise seemed fine. I didn't have any contact cleaner and the mechanic in the videos in this thread (https://www.ford-trucks.com/forums/1...explained.html) on the mayhem connector recommends against dielectric grease so I held off for now.

I did get an OBDII scanner and ForScan though! Got it set up and read codes with the ignition in ON but not running. No lights or warnings initially, but as I was reading through the code log, the lights and warnings came on, so I have a really nice before and after view.

Before: lots of DTC but they are all old (we got the truck used and I know it had work done so these could be very old). The only current DTC is for the Camera Module B115E:08-0A. Seems unlikely to be causing my main issue and we have an aftermarket backup camera because the tailgate is (we haul a truck camper) so my first guess is that.

After: there are several active DTCs (in addition to the probably unimportant camera one)...
- P2138:00 - Throttle/Pedal position sensor/switch D/E voltage correlation
----- I'll also note that this DTC showed up with the first scan but was listed as not present but did show a timestamp of yesterday morning which is the last time we drove the truck and had this issue).
- U0401:86 - Invalid Data received from ECM/PCM 'A'
----- This shows up in both the ABS module and in the IPMA module. In the IPMA module, it has information including the correct timestamp and a couple things that seem odd and I need to investigate (Outdoor temp of 43C - its 95F here and truck is in the sun so not shocking. ECU Power Supply Voltage at 11.8V - is this too low? ECU Internal temperature listed at 80C - this seems real high, truck hasn't been driven since yesterday).
- U0418:86 - Invalid Data Received from Brake System Control Module 'A'
---- This shows as present, but has a time stamp from last Sunday (which is when this problem first started happening). Weird that it showed as not present for my first scan, then shows as present for second scan but with a date from a week ago. I do see that the voltage was 13.5V (maybe only because it was running last weekend and not started this weekend), and that the ECU temperature was only 46C.

Two areas I'm going to look further into are the P2138 throttle/pedal code and why the ECU temperature would be so high even with the truck off.

 

Left side battery was replaced last year, right side is original. Got both batteries tested and they were both at 12.9V and amps in the 800+ range (over their stated), so that doesn't seem to be the problem. Not an expert, but I don't *think* this is the cause - see my DTCs below - so moving on to other ideas.

 

Read into the P2138 rabbit hole and the APP sensor seemed to be a common problem area. I took the readings for those at different throttle positions - see the attached image. Seems like VREF is my problem, but this might be the end of my diagnosis ability

 

I noticed all the initial system failures rely on wheel speed sensors/abs to function. Check the wires and connectors coming off the hubs to make sure there isn't anything obvious. If it's an intermittent issue, that may not be enough for the computer to flag the wheel sensors as an issue.

 

Great suggestion! I looked at all those wires and jiggled things while my wife watched the VREF readout. I didn't see anything obvious and she didn't ever see that change. Also did the same looking at connectors and wires around the PCM and elsewhere in the engine bay, throttle pedal and up under the dash and nothing looked out of the ordinary to my untrained eye.

 

Your problems may be related to communication on one of the busses. "U" faults involve communication issues. These faults can cause multiple warnings for systems in the vehicle. Now that you have a scan tool you can monitor everything and collect data when the faults return. It could be a bad module or sketchy connection in the bus.

Keep us updated. We always learn something new.

 

As mentioned wheel sensors have been known to cause these faults. These trucks are super sensitive to any disruption in voltage and continuity. Sounds like you have the optional dual battery set up on the gasser. If one is 5 years old it’s past due to be replaced. Replacing one was not a good idea. Were they disconnected and load tested separately? If not then the test was not accurate. If it was mine I’d drop two new batteries in it regardless with a mismatched pair. The factory batteries are known to have a short life 3-4 years.

A few years ago my truck was throwing a bunch of faults and shutting systems down. Even after diagnostic there was basically wild speculation on what was wrong since it showed so many codes and faults. It was out of warranty so I wasn’t going to throw modules at it. After some wire tracing it turned out to be a broken pin at a connector on the cab harness. Big problems, simple fix that a code reader can’t find. It will only tell you what the modules don’t like.

 

I agree, it's never a good idea to replace just one battery.

 

Ymmv but 100% of the time to date I have had these warnings show up it was an indicator of a failing battery. Not enough to show when checking voltage but just enough of a voltage drop at startup to screw up the module initialization.
Always change both batteries same time. Always have new batteries load tested prior to leaving with them. Battery companies used to rotate/test stock in stores but they haven't in years. So there is a potential to buy a brand new battery off the shelf that won't pass a load test. Learn from my mistake on that one.
I will also look forward to what you discover. Best of luck. Gremlins suck.

 

You should take apart the connector above the one you have already serviced and check that. I had water and corrosion in both connectors in my truck. Cleaning them resolved a number of issues I was having with systems that use the medium speed network.