I have gauges to MONITOR what's up with my truck's performance. If gauges had any relativity to causing FAILURE then all the big rigs would not have them as standard equipment. Dodge puts them in their Freightliners, so, what's the issue? I can see where they might be able to refuse you an exhaust manifold if it cracked where the pyro was installed, but to void your whole warranty - get real. It is against the law in all states to void an entire warranty when something installed causes something to fail, they can only void the part involved and they have to prove it caused the failure.
As far as what that specific dealer told you, ask them to put that statement in writing on their letterhead for you OR give you something in writing from DC that makes that statement. I bet you will very quickly get a retraction. If they do put it in writing, send a copy to DC and ask them WHAT'S UP WITH THIS? Your manual, your sales contract, nothing says any of that nonsense AND they cannot change the warranty rules as the go to suit their own purpose and design. If they want to play the game that way, then you are entitled to money back equal to the value of the warranty on your truck. Start chattering in that direction, get their attention. How much do you suppose is rolled up in the price of the truck for warranty coverages? You could make them give mfg cost accounting details via a lawsuit and also make them refund the value. That HAS happened already, DC has paid out several claims in that direction, and also has just reinstated warranties when it came down to the wire. As far as some regional rep having the power to just void a warranty, there is always someone higher up, and I would certainy take a trip up the ladder if someone tried to pull that on me.
My dealerhip questioned my gauges, I asked them if there was a problem, they said no. They also said that the installation was impeckable down to every detail. That told me they really took a close look, or were looking for something. My only comment to them was - these trucks are having some problems with EGT's in the #5 and #6 cyls, dropped valves, burn't pistons, etc, I want to be SURE about the operating temps, I haul animals and do not want to be sitting alongside the road BECAUSE I did not see a problem coming. I went on to tell them that I also knew that these trucks were having problems with fuel pressure, so the fuel pressure gauge was there to monitor the fuel presssure, same for the rail pressure gauge. I also told them they could see more gauges regarding transmission temp, diff temps, and anything else I might desire to monitor. I installed a GDP 2-micron fuel filter - once again they said something. I told them that ultimately GM and BOSCH recommended the 2-microns to stop the cavitation problems from junk in the fuel. Since DC has only recently changed to 7-microns and it is KNOWN that 2-microns is better, I thought the filter would be the better answer regarding the injector problems BECAUSE it would solve it from the fuel angle, only thing left in any injector argument is just the injector and then it should NOT be a warranty issue. Now I have installed an oil bypass filter, I suppose I will have to also explain that to them too. Fact is, all that I have done to my truck is with PREVENTION in mind. There are thousands of trucks with all this stuff on them having NO problems whatsoever and in fact this stuff has helped to diagnose a problem long before it has caused serious damage, so it ultimately will save them in warrnaty overhead.
You just have to have your facts in order, your arguments in order, and when all else fails you, change dealers, contact DC in writing with a registered letter, or get a lawyer. You are making payments or have paid for the truck, it is you property, you have a warranty that clearly states the terms, don't be afraid to exercise your rights to choose those things that you would like to install in your truck for your own information or pleasures.
CD
Attention: TDR Forum Junkies 
