this has been an issue for several years now but I only put 5,000 km a year on the car. you will be driving along and car will go to failsafe mode, stop turn engine off then restart and all is well. It usually happens when the car is hot and the warmer it is outside the better the chance.Code reads Throttle position sensor inconsistent with mass air flow sensor. My question is, is there a way to test these sensors or do I have to replace one of them or both

 

Start by cleaning the connecting plugs with electronic cleaner and the mafs with maf cleaner.

 

Though likely to be a dirty MAF, iP1121 can also be caused by a simple thing like the throttle cable being out of adjustment, thus putting the pedal sensor and throttle position sensor too far out of sync.
Adjustment method here, Post 5

https://www.jaguarforums.com/forum/x...ustment-92897/