Throwing multiple loss of comm codes
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Throwing multiple loss of comm codes
2015 Ford F150 5.0 4x4. I have been having an intermittent issue with lights popping on but its getting worse first i will have warning about abs off, hill start assist fault, traction control etc. It will just as fast disappear. i will get the orange wrench on the display that will go away once i shut down for a while. this morning when i started i now had steering errors and had no power steering for a while. it went away on its own and drives fine now. I hooked it to a scanner and it have several codes for loss on communication between the following: instrument panel, ecm/pcm a, body control module, transfer case module, steering column control, and invalid data. This has to be a plug or something. any one have any ideas where i can check or maybe something they have seen?
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I was going to start looking at that. I have heavy AFM lights and accessories. and i have done everything with 125% wire size and ran all wires correctly. There is a much bigger battery in it than originally came with the truck.
Lead Driver
Joined: Dec 2016
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From: GA
2015 Ford F150 5.0 4x4. I have been having an intermittent issue with lights popping on but its getting worse first i will have warning about abs off, hill start assist fault, traction control etc. It will just as fast disappear. i will get the orange wrench on the display that will go away once i shut down for a while. this morning when i started i now had steering errors and had no power steering for a while. it went away on its own and drives fine now. I hooked it to a scanner and it have several codes for loss on communication between the following: instrument panel, ecm/pcm a, body control module, transfer case module, steering column control, and invalid data. This has to be a plug or something. any one have any ideas where i can check or maybe something they have seen?
The scanner you have will not tell you the full story of what’s going on.
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To be honest, the only way you’ll truly find out what’s causing these problems and throwing the codes, which are stored in the system regardless if they go away or not, is by taking it into your Ford dealer of choice or any shop that has the proper equipment.
The scanner you have will not tell you the full story of what’s going on.
The scanner you have will not tell you the full story of what’s going on.
I agree but you never know who may give a hint of a similar story. I can guarantee any non dealership shop has a scanner like mine. I usually get the newest snap on model and update it every six months. The only info i do not have is the subsequent codes causes and they erroneous codes triggered. .
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Update:
Brought it to the FORD dealer. They were able to pin point it to the GEM module. Its the little black back that has the OBDII plug molded in. They swapped it, programmed it and said everything was talking properly again. about a week later same symptoms started. Only this time more frequent. almost every 4 ish days now.
Brought it to the FORD dealer. They were able to pin point it to the GEM module. Its the little black back that has the OBDII plug molded in. They swapped it, programmed it and said everything was talking properly again. about a week later same symptoms started. Only this time more frequent. almost every 4 ish days now.
Lead Driver
Joined: Dec 2016
Posts: 5,650
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From: GA
Update:
Brought it to the FORD dealer. They were able to pin point it to the GEM module. Its the little black back that has the OBDII plug molded in. They swapped it, programmed it and said everything was talking properly again. about a week later same symptoms started. Only this time more frequent. almost every 4 ish days now.
Brought it to the FORD dealer. They were able to pin point it to the GEM module. Its the little black back that has the OBDII plug molded in. They swapped it, programmed it and said everything was talking properly again. about a week later same symptoms started. Only this time more frequent. almost every 4 ish days now.
Sorry to hear that you’re still having issues and hopefully when you take it back to the dealer, they’ll be able to get it right.
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1st Gear
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Did you ever figure out the problem of this?
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4wd High
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Update:
Brought it to the FORD dealer. They were able to pin point it to the GEM module. Its the little black back that has the OBDII plug molded in. They swapped it, programmed it and said everything was talking properly again. about a week later same symptoms started. Only this time more frequent. almost every 4 ish days now.
Brought it to the FORD dealer. They were able to pin point it to the GEM module. Its the little black back that has the OBDII plug molded in. They swapped it, programmed it and said everything was talking properly again. about a week later same symptoms started. Only this time more frequent. almost every 4 ish days now.
Fleet Mechanic
Joined: Jan 2023
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This type of error needs real troubleshooting. A module may be bad or the CAN wiring may be damaged or connector corroded. You need a scan tool and ideally an oscilloscope to look at the network signals. Dealerships are notorious for swapping modules without fixing the problem.
Watch some South Main Auto YouTube videos. He repairs several Fords with network errors. You will see what types of checks you can do to hopefully find the problem. His customers frequently have broken or corroded connections due to rust from the road salts. You will have to go through the numerous video titles to find one that may apply to your situation.
Watch some South Main Auto YouTube videos. He repairs several Fords with network errors. You will see what types of checks you can do to hopefully find the problem. His customers frequently have broken or corroded connections due to rust from the road salts. You will have to go through the numerous video titles to find one that may apply to your situation.
4wd High
Joined: Sep 2025
Posts: 9
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This type of error needs real troubleshooting. A module may be bad or the CAN wiring may be damaged or connector corroded. You need a scan tool and ideally an oscilloscope to look at the network signals. Dealerships are notorious for swapping modules without fixing the problem.
Watch some South Main Auto YouTube videos. He repairs several Fords with network errors. You will see what types of checks you can do to hopefully find the problem. His customers frequently have broken or corroded connections due to rust from the road salts. You will have to go through the numerous video titles to find one that may apply to your situation.
Watch some South Main Auto YouTube videos. He repairs several Fords with network errors. You will see what types of checks you can do to hopefully find the problem. His customers frequently have broken or corroded connections due to rust from the road salts. You will have to go through the numerous video titles to find one that may apply to your situation.
If any one could possibly spot any corrosion or burnt or chewed or broken wires i would live them forever.
From the rear passenger tail light to the junction box I've opened up the entire harness, all my wires & connectors look as if they just came out the factory.
My fuel tank is on the floor, I've removed the timing belt cover to inspect..
I even got a new bcm & here's a whole thread on the F-150 forums about what else I've done:
https://www.f150forum.com/f38/crank-no-start-start-but-dies-immediately-not-fuel-pump-not-fpdm-not-fuse-576612/?utm_source=share-link&utm_medium=button&utm_campaign=share&utm_cont ent=post
These are photos from today Sept 14 2025
Last edited by 2o1ofx4; Sep 14, 2025 at 01:51 PM.
Fleet Mechanic
Joined: Jan 2023
Posts: 1,316
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You don't lack initiative, but you need information and a plan. Find or buy a set of wiring diagrams. Carefully map out the separate CAN networks. HS CAN is typically for critical functions like engine, brakes and safety. MS CAN is for lights, audio, climate etc. See if you can find a correlation between the comm faults and the separate networks. Then troubleshoot that network using an O-scope, measuring termination resistance etc. I'm no expert but I would watch instructional videos and read as much as possible. Isolate sub systems if possible. A faulty minor module may be affecting the network....who knows?
But I would waste money on my own diagnostic tools before I gave the dealership another dime. Maybe a local independent shop will be more helpful but they need to be good at these types of problems.
But I would waste money on my own diagnostic tools before I gave the dealership another dime. Maybe a local independent shop will be more helpful but they need to be good at these types of problems.
Cross-Country
Joined: Nov 2018
Posts: 51
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Why did you undo your whole loom? - Personally I would take it to an auto electrical place. We have a chain of shops called AES "Auto Electrical Services" around my area. Before you start unlooming things I would have tested the resistances of the wires to see if any are clearly compromised. You can cross reference the circuits with the diagrams from alldata. The way your trying to diagnose is like looking for a needle in a haystack and now any auto electrical mechanic you take it to is going to decline the work or at least I would.
I would put your truck together. Spit shine her up and take her down to carmax. If you have a back up truck then take her to the shop and have a professional diagnoses completed which on something like this takes a real pro and takes some time.
I would put your truck together. Spit shine her up and take her down to carmax. If you have a back up truck then take her to the shop and have a professional diagnoses completed which on something like this takes a real pro and takes some time.
4wd High
Joined: Sep 2025
Posts: 9
Likes: 0
You don't lack initiative, but you need information and a plan. Find or buy a set of wiring diagrams. Carefully map out the separate CAN networks. HS CAN is typically for critical functions like engine, brakes and safety. MS CAN is for lights, audio, climate etc. See if you can find a correlation between the comm faults and the separate networks. Then troubleshoot that network using an O-scope, measuring termination resistance etc. I'm no expert but I would watch instructional videos and read as much as possible. Isolate sub systems if possible. A faulty minor module may be affecting the network....who knows?
But I would waste money on my own diagnostic tools before I gave the dealership another dime. Maybe a local independent shop will be more helpful but they need to be good at these types of problems.
But I would waste money on my own diagnostic tools before I gave the dealership another dime. Maybe a local independent shop will be more helpful but they need to be good at these types of problems.
https://charm.li/Ford/2010/F%20150%2...20Scan%20Tool/
These are factory troubleshooting manuals to pinpoint where the problem is. All of them passed.
4wd High
Joined: Sep 2025
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And that's exactly where I'm at - I've had technician come with IDS software and the last one said it's between the accelerator pedal and the junction box. So i opened the harness hoping i would find something like in this video @7:20 mark
It was my last hope of finding something bad. Now I'm at the ABS module and thinking of pulling a main harness from a junkyard truck but i can't find a 4x4 super crew cab nearby.