Key Fob Confusion

[dirtwarrior]

Here is something to try and a lock smith has to do it. You may have to many fob assigned to your car. Have him erase all fobs and then prograM yours

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[Asim]

Thank you for the suggestion.
Can anyone confirm that if they both work in the cupholder, than it is not a question of programing?

 

[ORRadtech]

Here is something to try and a lock smith has to do it. You may have to many fob assigned to your car. Have him erase all fobs and then prograM yours

Consulting a locksmith is a good suggestion. In addition to clearing and programming fobs the should also be able to tell if they are, or aren't, transmitting. Their equipment may also be able to tell if the module is working and/or receiving a signal.

Thank you for the suggestion.
Can anyone confirm that if they both work in the cupholder, than it is not a question of programing?

As I said before, the fob can be completely dead and work in the cup holder. If the car didn't recognize the fob the car wouldn't start. If that's what you're asking then, yes, the fobs/module are programed.
The fact that they work in the cup holder but not remotely indicates, to me, a problem with either signal transmission or reception.

 

[Asim]

Great suggestions and taken to heart. Had a mobile key fob guy test the fobs and both are transmitting (and continue to work in the cupholder only).
It's defiantly on the receiving side now. Anyone know where I can find a wiring diagram for the receiving / antenna or additional tips now that we've ruled out the fobs?

 

[dirtwarrior]

For me before I dive into a diagnostic of car would be delete fob programming and reprogram

 

[luca1290]

Great suggestions and taken to heart. Had a mobile key fob guy test the fobs and both are transmitting (and continue to work in the cupholder only).

The system which reads the keys in the cupholder is different from the system which reads the keys actively.
We got it, the passive reading system in the cupholder is working, great, now we have to debug the active system which reads the keys for starting the car.

Two questions:
1- Does the car locks and unlocks via the door handles when it's cold? Don't use the fob buttons, use the sensitive pods on the door handles.
2- Do you have a way to diagnose the car via Forscan?

The antennas which opens the door and the boot lid are located into each door and into the boot lid proximity.
The antenna which starts the car is located inside the central tunnel. That or it's cabling may be defective in a way that's reactive to temperatures (and that can happen with solid state electronics) as noted by @Skye.

 

[Skye]

Attached are diagrams, highlighting on a 2017, where the fob antennas are. These are more for orientation, before removing the panel/s. Maybe focussing on one sensor and its interaction will help isolate the root cause.

Edit,

Early on, the car's battery was replaced. The battery and charging system continue to work correctly, yes? Was a BMS reset completed after the battery replacement?

https://www.mustang6g.com/forums/threads/bms-reset-no-tools-required.151602/

It shouldn't have impact on doors and security; this does seem to be a unique issue. But, ya never know...The reset is something to do after battery replacement, no matter what else is going on with the car.

The problem still points to some odd, systemic issue. AFAIK, the trunk sensor feeds into Body Control Module-B (trunk), the doors, BCM-A (interior, floor, right kick panel). To have one or the other act up, OK. But none of those work with the fob? Or when cold?

Recent car purchase. No aftermarket security apparatus installed? Dealers have been known to hide sensors in the car, so if the car is stolen or the buyer stops payments, they can locate and recover. They use vampire taps and clip onto or insert in-line these receivers and transmitters near BCM-A or under dash. Any "weird" electronics seen in those areas? The OBD port?

Here's an example:

https://www.mustang6g.com/forums/th...s-on-all-newer-cars-eye-opening-video.202536/

They often install these units in association with the OBD/GateWay Module, the centerpiece hub of the car's electronics. A crappy dealer install (common), bad electrical connections and phantom electrical drain in these areas could be throwing things off. If you can't readily find something or are not sure, contact the dealer and confirm nothing is installed on the car.

^ This all ties into the idea of a poor electrical connection (or a logical fault) at one point.

Edit (again),

BCMB - Body Control Module-B (in the trunk)
DDM - Driver Door Module (Keyless Entry)
RTM - Radio/Remote Transceiver Module (keyless entry, TPMS, remote start)

In the last diagram, see the GateWay Module (GWM). Look at the network segment to the left. Everything associated with this issue is on that segment.

I'm not saying wiring is the problem, but it does go back to a systemic failure. I highlighted the special "dealer add-on" above. Could also be a failing GWM. Could be a loose connector in the area of the OBD/GWM.

I think a thorough visual check in the area of the OBD/GWM could be worthwhile.

 

[Asim]

Update - we have a suspect in custody. Ran an OBD2 scan tool and low and behold we have: U0258-87 "Lost connection with radio transceiver" . That's the module in-between the rear speakers I believe.?
2 root causes - The car was tinted and I asked the tint be removed, so could have been some neanderthal-like tint guy. Secondly, I noticed the rear camera was replaced (common problem I've seen) and that wire is in the same loom under the deck lid. Still don't know exactly if the device is bad, or wire to / from is shorting / loose, but I think you will agree, that is main area of
focus.
Like Skye says above ^ This all ties into the idea of a poor electrical connection (or a logical fault) at one point.

 

[ORRadtech]

The early S550s did have a wiring issue with the harness that goes from the body to the trunk lid. Wires would break from the flexing of a too tight harness. The most common symptom was loss of the rear camera signal to the APIM but I don't believe the camera itself was faulty.
It is certainly a good place to start your search.

 

[Asim]

SOLVED!
Hopefully help someone else who might go through the same thing. The problem ended up being a broken pin inside the wiring plug that is just after the BCM, connecting the wires to the back. The antenna power is actually only 2A to run the relay inside of it, which is a very thin wire. That wires pin somehow came off in the plug.

Thank you to the mustang family for the guidance and support.
Much love.

 

[deanm11]

In case anyone needs to see what the FOB antenna looks like (Under cupholder) from my 2022 GT

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