2021 Ram 1500 Big Horn Fuse Diagram and the BCM

[msherwood87]

I bought my '21 Ram 1500 a few weeks ago. It had a battery drain and has been at the dealers for 10 days now and they don't know what's wrong. They think it has something to do with the body control module (BCM). Anyways, I had a radar detector I installed the day I got it using a fuse jumper and fuse F66 (run - accessory feed). They are trying to violate FTC Magnuson-Moss Warranty Act and refuse warranty solely because this was installed (they don't know what's wrong, so they cannot demonstrate that this was the source). They think there's a short in the BCM and want to replace it; however, if the radar detector cause the short then why is F66 still live and the radar detector still working?

What I am calling upon here as a community, does anyone know if fuse F66 is even connected to the BCM. It's really hard to find even the fuse box diagram online for this truck, so I was hoping someone may have wiring diagrams.

 

[Jimmy07]

I bought my '21 Ram 1500 a few weeks ago. It had a battery drain and has been at the dealers for 10 days now and they don't know what's wrong. They think it has something to do with the body control module (BCM). Anyways, I had a radar detector I installed the day I got it using a fuse jumper and fuse F66 (run - accessory feed). They are trying to violate FTC Magnuson-Moss Warranty Act and refuse warranty solely because this was installed (they don't know what's wrong, so they cannot demonstrate that this was the source). They think there's a short in the BCM and want to replace it; however, if the radar detector cause the short then why is F66 still live and the radar detector still working?

What I am calling upon here as a community, does anyone know if fuse F66 is even connected to the BCM. It's really hard to find even the fuse box diagram online for this truck, so I was hoping someone may have wiring diagrams.

F66 is an unused run/accessory circuit. It is run off of an integrated relay (your radar detector is using pin 87 of that relay). This relay’s trigger coil pin 86 is run by one of the BCM’s delay relay control circuits. This is what makes retained accessory power possible (when you shut the truck off and you still have power for x amount of time until a door is opened). It’s not the fact that your radar detector still works, but does it stay on all the time, even after the truck is off and you exit the truck? If it does, then does your power port above the radio ALWAYS have power, also, even with the truck off? If this is the case, then yes, there is a problem with that delay control circuit on the BCM constantly supplying the power to keep the relay coil triggered.

 

[msherwood87]

F66 is an unused run/accessory circuit. It is run off of an integrated relay (your radar detector is using pin 87 of that relay). This relay’s trigger coil pin 86 is run by one of the BCM’s delay relay control circuits. This is what makes retained accessory power possible (when you shut the truck off and you still have power for x amount of time until a door is opened). It’s not the fact that your radar detector still works, but does it stay on all the time, even after the truck is off and you exit the truck? If it does, then does your power port above the radio ALWAYS have power, also, even with the truck off? If this is the case, then yes, there is a problem with that delay control circuit on the BCM constantly supplying the power to keep the relay coil triggered.

Thanks for the quick response. The F66 fuse works as its supposed to, turns on on run and off after the delay or door open. I don't think there's anything wrong with F66 or anything cause by the radar detector but the dealer is trying to void warranty solely due to the radar detector installation.

 

[msherwood87]

So if F66 and the radar detector still function normally, is there any chance this would have caused a short or issue in the BCM that would then cause the headlamp switch to stop working along with a 14-hr complete battery drain?

FCA has not yet denied warranty coverage but they and the dealer keep stating that anything aftermarket connected to the electrical system would immediately void the warranty, which is against federal law requiring them to "show that the aftermarket or recycled part caused the need for repairs before denying warranty coverage."

 

[Jimmy07]

So if F66 and the radar detector still function normally, is there any chance this would have caused a short or issue in the BCM that would then cause the headlamp switch to stop working along with a 14-hr complete battery drain?

FCA has not yet denied warranty coverage but they and the dealer keep stating that anything aftermarket connected to the electrical system would immediately void the warranty, which is against federal law requiring them to "show that the aftermarket or recycled part caused the need for repairs before denying warranty coverage."

You’re in a catch 22. How did they determine the BCM is the issue? Did they do a current draw test by pulling fuses one by one? You can make them diagnose and chase down exactly what the issue is, and if they somehow determine it’s the radar detector, you’ll be on the hook for all that time, and that’s before they actually fix it. THEN it’s up to you to try and dispute that. All I can say is, you used an unused available fused circuit, which presumably is what it’s intended for, and there doesn’t seem to be any issue with that actual circuit. I would just start by asking them exactly how they are making their determination, and ask them to point out exactly where in the warranty writing that anything connected to the electrical system would immediately void the warranty.

 

[msherwood87]

You’re in a catch 22. How did they determine the BCM is the issue? Did they do a current draw test by pulling fuses one by one? You can make them diagnose and chase down exactly what the issue is, and if they somehow determine it’s the radar detector, you’ll be on the hook for all that time, and that’s before they actually fix it. THEN it’s up to you to try and dispute that. All I can say is, you used an unused available fused circuit, which presumably is what it’s intended for, and there doesn’t seem to be any issue with that actual circuit. I would just start by asking them exactly how they are making their determination, and ask them to point out exactly where in the warranty writing that anything connected to the electrical system would immediately void the warranty.

Man your on it. Thanks. They haven't identified it as anything right now. This is the type of stuff I am getting "I will be upfront and let you know that I have not informed them of the hard wired radar detector. If I do they will stop with the help they are providing and automatically decline coverage. " they have had this truck for 14 days and don't know whats wrong with it exactly but want to replace the bcm, which has an eta of Jan 6, putting it past the 30 calendar day requirement in ohio for lemon law.