Hello!  I installed a 8800 in my 2005 Chevy Suburban.  Wired to the battery post, good ground, NMO antenna through the roof.  When I key up on VHF it causes the gauge to dip until it hits zero then the chimes come on and and oil pressure warning.  I let off the mike and it goes back to normal.  It doesn't do it on UHF.  Here is the thing, I isolated the power by running the radio off a battery, still does it.  I ran a separate antenna and mount (inside the vehicle), still does it.  It even will do it with my handheld, though not as pronounced due to the 5w limit.  When I dial the power down on the 8800 it isn't as bad, but it still happens.

So I am at a loss.  The gauge console was rebuilt a few years ago, maybe they put in some substandard gauge motors?  

Any advice?

Thanks and 73s.

Most likely, RF is being induced into the oil pressure gauge wiring. The wire length may be resonant on the 2m band thus  providing a high level RF voltage into the ECM's analog input.

I assume you already checked the oil pressure transducer's connector for corrosion or a bad connection.

Try to put some "snap-on" RF chokes on the oil transducer wire or the oil transducer wiring harness. It's best to wrap the wire(s) around the choke several times it the wire is long enough. If it's short, simply put several chokes over the wire or the wiring harness. Also, placing a choke as close to the ECM (the engine computer) will make it more effective but unfortunately it's not always possible. Just place it where you can and see if it helps.

Next step would be to try "grounding" or should I should say - bonding the engine to the body and the frame in several places. I like to "ground" the exhaust pipe to the chassis in several places with a flat 1/2" ribbon.

If this does not help, perhaps adding a 10 uF capacitor between the oil pressure analog input and the chassis ground may help to eliminate any stray RF.

Adding a bandpass filter to the radios output may cut off some harmonics that may potentially cause this issue. I would do this after trying all of the above.

Hope this helps some.

Yep, it's RF getting into the electrics.  I had a Chevy car where the RPM gauge would peg when keying up with a 2M handheld.

The cruise control in my wife's '90 Buick would decrease speed by about 20 MPH when she transmitted on 2 Meters. She very seldom used cruise control, so I never looked into a solution.

I have the exact same problem with my 2005 Chevy Avalanche.  It started after I had the oil pressure sensor replaced.  I'm not sure if the new sensor was more susceptible to RF or if they changed the wire routing during the repair.  I just ignored it and eventually the problem stopped, which I can't explain.

Thanks for the replies.  I wouldn't worry about it but I wonder if the gauge going to zero and triggering the chimes and warning on the message center might also affect other functions and inputs in the ECM, potentially causing a limp mode situation or other serious side effects.

Mine used to "lurch" whenever the transmitter was keyed.

It never wandered off speed - Just acted like it was startled for a second.

My 70cm HT would click off my kitchen GFI plug.
Remote control now possible with my HT :-)

Might check your coax where it plugs into the radio with a antenna analyzer.  Might have a high swr which is the main problem.   Also add a ground wire from the radio to the chassis, I know the ground wire from the power is a good ground but more might be better.  Have not heard about noise from vhf into car electronics so this is something interesting to me.  I hear much talk about HF in car electronics, but when I had a mobile in the truck the noise was so bad I had to turn off the truck to listen..  Keep us updated..

Prosise

+1 to Gyprat's reply