Reasons you have been denied warranty claims w/ any Toyota over the years?

Have you ever had a warranty claim denied due to something you did not do or that they did not accept as done properly (work not done by dealer or other retail mechanic). Basically, have you been denied a claim because you are a Do It Yourselfer (like me) and they did not accept that proper work was done even when you produce dated receipts for parts/fluids you used to do the maintenance items? We are mainly talking oil and oil filters on the Prius, but also coolant, engine air filter, etc.

I am very familiar with what 'should be acceptable' from a fairness point of view. But many (most?) insurance companies have whole departments devoted to denying claims, so I'd like to hear from people who have had major warranty claims covered -OR- denied (and for what reason). Especially when you have been the DIY mechanic for the scheduled maintenance.

New Prius Plug In owner here. Of the new cars I have had over the years, I have (thankfully) never had a major covered warranty item fail where Toyota/it's insur company had to pay out thousands for a warranty claim.

 

Tks for the link. A very good reminder to do your research on your particular repair issue and if dealer back peddles, go their and get specifics face to face of why they want to deny the claim. Armed with knowledge, common sense and you and them being there to see the specifics of the issue, can ameliorate much of a dealer' smoke and mirrors reasoning.

Also, I like getting a case started with Toyota care at the first wiff of problems like the linked OP did.