Undercoat Voids Warranty
 

Good evening Mazda owners.
I write this post to ask for your input or at the very least to inform potential Mazda customers.
I purchased a 2015 Mazda CX-9, new from a Toronto Dealership.
I put Krown Rust control on it the first year, 2016 and then again in the fall of 2017, around the beginning of November.
on about January 3, 2018 my engine light came on.
I took it to my local Mazda Service Center.
After a very brief time the service manager appeared and asked if I had undercoated my vehicle.
I said yes.
The service guy said that my problem was the fuel tank pressure sensor, but that Mazda would not repair this under the 5 year unlimited warranty because of the undercoating.
The code for the problem was p0451.
I then spoke with my own mechanic, certified and licensed owning his own garage for many years.
Both he and his colleague stated that they strongly disagreed.
I again spoke at length with the local Mazda service guy who then changed his story from the fuel tank pressure sensor being plugged with rust proofing to the “atmospheric pressure vent” being plugged with rust proofing.
I spoke with Krown who contacted their head office.
Krown said that if indeed the problem was caused by the rust proofing they would,pay for the problem.
Not trusting the. Adda service dealer, I decided to pay for my mechanic to test my vehicle.
His diagnosis was that indeed the fuel tank pressure sensor was faulty but that there was no rust proofing clogging
any vent or indeed anywhere on the fuel tank sensor line.
I spoke with the dealership where I purchased my vehicle, in Toronto and was advised to call Mazda’s Head Office.
I spent much time on the line with Mazda.
From the get go all Mazda wanted to say was “did the rust control drill holes in your car?”
I stated I was no sure, and asked why.
Then I was told by Mazda Head Office that “it could void the warranty”.
I had asked many times where this was written.
I was continually and repeatedly told that drilling holes in my vehicle “could” void the warranty.
I asked what do you mean “could”?
I was told that if it was found to cause damage to any part.
I asked my mechanic who said there is no way for the rust proofing that was done would have anything to do with
the area of the faulty gas tank part or area.
No matter, I have been told Mazda will not cover the cost of the faulty fuel tank pressure sensor.
I am now concerned that my entire warranty will go un-honoured because of a loop-hole Mazda has found and never told me about.
I ask if anyone else has had this problem.
Any input appreciated. Signed, NoWarranty

Potentially the undercoating has insulated the sensor & caused it to overheat & fail. Unlikely but possible.

I think, they are thinking you have "modified" the car by applying the rust proofing.

Unfair? Yes. Unjust? Yes.

Not at all. The worst that could happen is that anything you did (or had done) that caused a problem would result in that problem not covered by the warranty. If the rust coating actually caused the failure of the sensor, then Mazda won't pay to replace the sensor. This makes sense. If the drilled holes rust on the edges or let salt into parts otherwise sealed, then Mazda's corrosion warranty won't pay to fix that corrosion problem caused by the application of the aftermarket product. This also makes sense.

There is no way any action renders the entire warranty void.