Driving in town, going through a round-a-bout (US!!) and the car slowed and "reduced performance" came up on the instrument cluster as well as the check engine light. I carefully drove the 6 miles back home, back roads, 45 mph., engine temp normal, tach normal, Dynamic mode inactivated and I didn't even try to mess with the switch. I'm thinking/hoping that it's the O2 sensor, now continued under warranty by JLR. Any other ideas? warnings? I have an appt for other stuff on Dec. 12, so may just wait.

 

When I had an O2 sensor go, I got the CEL but not the "reduced engine performance" warning. You could use a reader to pull the codes and see what they are, then do the battery module reset; however, that might clear something useful to the dealer. Maybe see if the dealer can take the car in early, given the change in circumstances?

Either way, good luck!

 

If you have a code reader read the codes and that will give you a clue. Some car parts stores will let you borrow or rent one if you don't have one.

As Lizzardo said a bad O2 sensor doesn't always trip limp mode. My car has had bad O2 sensors and the car still ran fine except for CEL light and reduced fuel economy.

In the past with my cars a bad MAF or other sensor/sensor connector (like temperature, vacuum, boost or crank angle) or bad vacuum leak was usually the issue.

 

So finally talked to service manager.. dealership only has one Jaguar service writer who is out on training this week. He said that unless the check engine light is flashing that there is nothing serious going on... and the car is driveable and it's probably the O2 sensor and that there have been alot of problems with them. I know JLR lengthened the warranty claim period on them, so hope I can get it done now. I don't need to drive it and so he said to just wait for the appt. I may just go out and check the car again. It did this last year in December in the driveway and it was just the 02 sensor. That was on my worklist for Dec. 13 anyway. Will provide update.

 

Did you try restarting the engine? Sometimes an intermittent can trigger a symptom.

Prob just the high G force from the roundabout!

 

Not yet, planned for Thursday. I love it, g-force in the roundabout....how did you know... just an autocross addict getting in some practice? LOL. At least no cones to knock over!

 

So, mid December update. Never did have opportunity to see if CEL was still on before going to dealer this past Monday, but it was still on when I drove it there. Took the back roads and drove very conservatively 50-55 and no AE. My preferred tech is at school, but will be back on it next week, so hope to have more info. It's in for its 48 month service, a snapped gas cap tether, an AE switch ( I have manual trans) that won't raise the spoiler for cleaning, a "clink/tink" noise in the forward area of the right side door, and a determination if this MY 2017 has those 2-piece flanged coolant pipes that are prone to splitting. May get it back late next week, but not counting on it.