Does power wire (2awg) connected to battery produce a radio frequency that interrupts fobs?

[cpassmore1]

I've been experiencing odd behavior with the way car acts with key fobs after stopping (won't recognize lock signal unless next to car). This ONLY happens after stopping, not if it's in garage/parking lot and sitting for 5-10 minutes. Tech said he talked to their contact at Ford engineering (seems extreme… but whatever) and they're saying that wires connected to the battery can generate radio blocking frequencies that 'jam' fobs.

Tech unhooked battery wire and isn't experiencing any issues with locking/unlocking car.

I'm not sure I believe this… but has anyone else experienced this? Everything is grounded back to the battery.

 

[UNBROKEN]

If that were the case every car with an aftermarket audio system or anything else hooked to the battery would have issues with the key fob. They do not.

 

[cpassmore1]

Well… crap. Per Google AI (Gemini)


How Your Car Stereo Jammed Your Key Fob

• Class-D Amplifier Noise: Most modern car amplifiers (especially compact or high-powered subwoofer amps) are Class-D designs. They function by rapidly switching transistors on and off at high frequencies (often hundreds of kilohertz). This switching creates Radio Frequency Interference (RFI).
• The 2 AWG Wire Acts as an Antenna: If the amplifier lacks proper internal filtering or shielding, this high-frequency electrical noise travels backwards out of the amplifier's power terminal. Your long, heavy 2 AWG OFC power wire acts as a giant, highly efficient antenna that broadcasts this noise throughout the vehicle cabin.
• Receiver Blinding: Key fob receivers are highly sensitive but transmit very weak signals. The RFI broadcast by your power wire completely drowns out the faint signal from your key fob, "blinding" the car's receiver.

I have 3 JL Audio VXI amps in the back (Class D). I guess if they were A/B this wouldn't be an issue? I can see how this might cause an issue when the car is still powered on (just got out and shut door) and is NOT an issue after it powers down (amps/system is off).

Now… I'll say I ran the ground wire all the way back to the battery because the navtv f25 device stated it had to have the same ground as the amps. One of the fixes is to shorten the ground wire.

• Relocate the Ground Wire: Ensure your amplifier ground wire is as short as possible (under 18 inches) and bolted directly to bare, unpainted chassis metal. A weak ground forces RFI to escape through the power wire instead of safely draining into the vehicle chassis.

Another is to clip ferrite cores close to the amp chassis… I don't have the faintest idea of where to source those. Amazon?

 

[cpassmore1]

Okay… so in addition… I've NEVER run a long ground before either… again… at the instruction of NavTV.


The Problem with Long Grounds

• It Acts as a Second Massive Antenna: High-frequency switching noise from your three Class-D VXi amplifiers does not just travel down your power wire; it also travels down the ground wire. You now have two giant 2 AWG wires running the entire length of your Explorer ST, effectively forming a massive "loop antenna" that doubles the RFI broadcast inside the cabin [1, 2].
• High Impedance at Radio Frequencies: A long wire has very low resistance to Direct Current (DC), but it has very high impedance (resistance) to high-frequency AC noise. To the switching noise of your amplifiers, that long ground wire looks like a wall. Instead of the noise draining away, it gets trapped, backs up, and radiates directly out of the cable into your Ford's wireless receiver [2].

Apparently there's two massive antenna's being created. Are there any existing grounding locations in the rear or do I have to tap my own?

 

[cpassmore1]

OMG… I took it in because I was having TPMS sensor failures as well… for future knowledge if anyone else runs into this. 2025 ST (w/ B&O)


In the Ford Explorer, the Remote Transceiver Module (RTM) is located toward the rear of the vehicle, mounted high up near the headliner/C-pillar area. This single module controls both your wireless key fobs and your Tire Pressure Monitoring System (TPMS). [1, 2, 3]

 

[UNBROKEN]

First, I don’t believe anything AI generated when it comes to car audio. The vast majority of what I’ve seen is wrong.
Second, I run a NAV TV unit in my car, it’s grounded to the battery per their recommendation and both of my amplifiers have a class D sub channel. I know multiple other people who are doing the same thing. None of us have any issues with our key fobs. My +/- runs from the battery are 0 gauge.

 

[cpassmore1]

I did not ground the nav tv to the battery… it's grounded via the harness which I assume ends up at the battery. Hindsight… it's probably the frame. My +/- battery runs are 0 awg as well (I mistakenly instructed the AI that I used 2).

I was POSITIVE the wire wasn't acting an as antenna… but I'm not so sure now after being told that the received is in the rear (where the amps are) and that the switching is what causes the radio interference. The FOBs work perfectly after a bit of time (system shutdown) and only have issues when powered on. TPMS sensors (obviously) only trigger after a bit of driving and then tech said when power wire was unplugged from batter everything functioned fine.

I'm not sure what to 'believe' at this point but WILL shorten the ground to somewhere in the rear (hoping for existing bolt or something). I have some spare wire… maybe I'll use that to confirm before cutting current ground.

Regardless… I have NEVER had/heard of this scenario as an issue.