[RFI] RFI issues in Toyota 4Runner

[Ray]

I have a 2006 4Runner that works fine with my FT-100 running barefoot on 
any band.  The HF antenna is a base matched 400 watt Hustler, mounted on 
the car top carrier frame.  The HF mount is exterior grounded to the 
roof at the frame mounting bolt.  The coax has about two feet of #43 
ferrite cores installed over it on both ends of the coax to absorb any 
RF coming back down the coax.   The system works very well on 20 meters 
and up, as I compete nicely with fixed stations for DX.

I also have an FT-7800 with an MFJ 150 watt amp on 2 meters.  The VHF 
antenna is mounted in the center of the roof on a magnet mount.  Both 
exciters are powered thru a TGE voltage regulator.  All works well in 
this configuration.

However I also have a Ameritron 500 watt HF amp installed on the back 
deck.  It is powered by two healthy gel cell batteries mounted there  
They are kept charged thru a heavy #4 (fused both ends), wire run 
underneath the body and connected directly to the car battery.  The car 
body is the return.  There is very little voltage drop on 70 to 80 amp 
voice peaks.   The FT-100 with the Ameritron amplifier at full power 
work well on 10,15 and 20 meters.

My problem: on 40 meters with the amplifier on, an oxygen sensor trips 
an alarm to the Toyota computer which puts the car into a protected 
running state, where it will not go any faster than about 35 miles an hour.

I can easily clear the fault with a code scanner. This indicates there 
is no permanent damage.  Once again running at 100 watts proves OK, but 
I have been unable to resolve how prevent the 500 watts of RF from 
getting to the oxygen sensor and/or computer on 40 meters.

Does anyone have any experience that would be helpful here?

Your attention is appreciated.
Ray, W4BYG