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@Butch88 Sorry the new TB didn't solve your problem. Being so intermittent it is hard to determine the root cause but I agree it appears to be a wiring problem. You need to have a real good look at all the wiring running from the pedal assembly to the PCM. Make double sure that all the pins are fully seated in the connectors and that all the pins are properly crimped to the wires. A bad crimp can be hard to see. Do the same for the harness running from the TB.
I went in this morning and cleared all the codes and then went out to run some errands. On the way back after a 40 or 50 mile drive the code popped up again. After pulling over and cycling the key on and off a few times the warning screens cleared and truck went out of limp mode and made the drive back to town.
fired up Forscan again and checked codes. In addition to the P2138 I had several other codes related to the problem:
1. OCS --U0401--Invalid date from ECM/PCM "A"
2. ABS--U0401--Invalid data from ECM/ PCM "A"
3. PDM--Lin Bus "A"
4. IPC--U0401 invalid data from ECM/PCM "A"
5. IPC--U0405: 82-0A
Truck has a new battery and seems to be charging fine. The APP has been replaced (twice) and has a new pigtail connector. There is also another connector on the left front fender that has a new pigtail connector and a bunch up tape on the wires from a previous (to me) dealer repair. Don't know the number of that connector off hand but its next to C216 where I tied in the 4 com wires for the BLIS upgrade I did. Blis has been working flawlessly.
I've been thinking what a guy really needs is a real Scan tool so can check live data, and access to service data to figure out these circuit.
Funky PCM or corrupted firmware.
I went in this morning and cleared all the codes and then went out to run some errands. On the way back after a 40 or 50 mile drive the code popped up again. After pulling over and cycling the key on and off a few times the warning screens cleared and truck went out of limp mode and made the drive back to town.
fired up Forscan again and checked codes. In addition to the P2138 I had several other codes related to the problem:
1. OCS --U0401--Invalid date from ECM/PCM "A"
2. ABS--U0401--Invalid data from ECM/ PCM "A"
3. PDM--Lin Bus "A"
4. IPC--U0401 invalid data from ECM/PCM "A"
5. IPC--U0405: 82-0A
Truck has a new battery and seems to be charging fine. The APP has been replaced (twice) and has a new pigtail connector. There is also another connector on the left front fender that has a new pigtail connector and a bunch up tape on the wires from a previous (to me) dealer repair. Don't know the number of that connector off hand but its next to C216 where I tied in the 4 com wires for the BLIS upgrade I did. Blis has been working flawlessly.
I've been thinking what a guy really needs is a real Scan tool so can check live data, and access to service data to figure out these circuit.
Funky PCM or corrupted firmware.
FORScan can monitor pretty well any live data that any other scan tool can.
Here are the connectors on the LH wheelhouse.
I would have a real good look at the wiring that was previously repaired.
Please, when you provide DTC information, give us the entire code. It should look something like P1234:56-XX like you did with Item 5. Each part of that code provides valuable information.
Here is what it looks like on my left front fender well. C316 is the one with the white lever. There doesn't seem to be a C268 as shown on your pic. Pigtail connector has a mass of wires taped up on the right side in pic and other end disappears down just to the left of the bundle of wires coming into C316.
I need to get all the schematics for the can system and trace where com circuits go from the PCM to the ABS and the other modules associated with the DTCs to figure out where the common link is. If I can find why one of them isn't working it will likely fix the others.
Here is what it looks like on my left front fender well. C316 is the one with the white lever. There doesn't seem to be a C268 as shown on your pic. Pigtail connector has a mass of wires taped up on the right side in pic and other end disappears down just to the left of the bundle of wires coming into C316.
I need to get all the schematics for the can system and trace where com circuits go from the PCM to the ABS and the other modules associated with the DTCs to figure out where the common link is. If I can find why one of them isn't working it will likely fix the others.
I've done a little more research and your truck is different from mine which is a 2016. That wiring all looks very suspicious. I would be pulling off the loom or covering on all that stuff and having a real good look at it. I have no idea what the orange connector is replacing. It is hard to tell with nothing but geen wires. My guess is the problem is with C1590 since that is the connector the APP wiring passes through. Here is the schematic.
C1590 is a 34 pin connector and I believe it is as noted below. It looks like the harness coming in from the front has been disturbed. I would start there.
Bought this 2020 XLT 302A a few months ago. It is setting this code VERY randomly. Might do it twice in a week. May not do it for a month. It will set then the symptoms disappear and truck will go back to normal operation till the next event.
A full carmax report show that the truck was at the dealer several times in its life for conditions related to this issue in it’s lifetime such as traction control, etc that are turned off if you loose the TPS. I see that the accelerator pedal and connector has been replaced. Also a connector on the left from fender has been replaced as I see green wires on it and a taped up harness there. I feel that someone passed their problem on to me.
nontheless is this a common issue with these trucks and what is the best solution to head to? Googling shows may be petal. (Not likely now), throttle body, ecm, or loose connectin/compromised wire.
Update: I misspoke when I said Carmax report. I was able to download a full service history from Motorcraftservice. This detailed all the visits at dealerships. The vehicle had basically been at a dealer for 22 visits over its 5 year history. Everything from oil changes to tire rotations has been done at two or three dealerships. There were some visits that had not details but several complaining of ABS and stabiltrack errors. The first thing that happens when you get the P2138 code is it disables those systems + cruise control, hill start assist, and a couple of others that don't come to mind right now and you will get limp mode for throttle response for a bit. Letting the truck sit for a bit, or disconnecting the battery usually puts the codes into history and normal operation till the next time.
Just had my 2017 f150 diagnosis done on the same issue and they said throttle body needs to be replaced.
Just a little update. I have been out of town for a few weeks so haven't had a chance to pursue this problem. I did get this off the interweb though This is wiring diagram for the interconnect between APP PCM and ETC on 2018 thru 2020 F150. They are all "home runs" directly from the pedal to the pcm and back to the throttle. Just as it should be for such an important circuit. The only connections are plugs at each component. Its either a bad pin at one of the connectors, a chafed wire, or an intermittent fault in the PCM.
I am leaning toward the PCM myself as I am also getting some other spurious communincation codes with the PCM on other components. The others just aren't critical enough to set the CEL or cause limp mode.
