The Check Engine warning appeared this morning while driving my '05 XK8. Oil pressure, coolant, etc.instruments all read normal. The user's manual simply indicates see your Jaguar technician immediately. Not very helpful. I would welcome any suggestions as to what may be the cause(s) of this warning and how critical is it to have it addressed "immediately".Thanks in advance for your feedback.

 

It's on for a reason, it might be important or not.
You need to get the codes read to understand what has caused the light to come on, Autozone, O.Reillys etc will read them for you.
Make sure they give you the actual code not just their interpretation of it then post it up here.

 

Engine check lights on old cars could mean a bunch of things. Some serious, some zero dollar fixes.

Codes would help, but in the meanwhile, with your car gauges reading fine, how is the car driving? Don't 100% trust the gauges unless your car had the RealGauge adaptation to read accurate oil pressure / water temperature.

Does it have a rough engine, lumpy, lean, running hot etc. Is there Blue/White smoke from the exhaust. Does car start ok, engine run on after turning off ignition etc. These all point the way to a root cause.

Before taking to a dealer - first up visual inspections, are things where they should be IE is the serpentine belt ok, are fluid level checked. Are caps firmly closed (including fuel cap), are pipes ok esp. look for vacuum leaks through holes in pipes. Are there oil/water leaks anywhere? Getting under the front of the car and looking around is always useful to see if something isn't right.

Then try "zero dollar" fixes - spraying the air sensor with MAF cleaner, checking all electrical contacts are ok (spraying with contact cleaner), tapping the thermostat tower in case thermostat is stuck, putting in a quart of engine oil, add coolant to reservoir etc.

Onto more serious things, like checking oxygen& temperature sensors, spark plugs, injectors, etc, which really depends on your confidence levels. Here you will definitely need the codes to guide you. How you feel the car is running is important. Does it feel underpowered now the light is on. It could be as serious as replacing injectors, spark plugs, coils and even your Catalytic converters, or it could be just a loose fuel filler cap and or a bad sensor.

 

You should get a code reader. An OBDII (onboard diagnostics) code reader. There are some that will work on your phone. I believe a lot of folks on here like the Torque app. They are not expensive. It will be a good investment in the long run, or even the short run. There is a sticky above called General Tech Help. If you look there, there is a whole section on OBDII Code Scanners. But, if you get the codes read, no matter how, come back here and post them and someone will have suggestions for sure !
Oh yeah, if your check engine light is on (CEL), you will have codes.

 

Check engine lights simply indicate you need to check something under the hood. Could be low oil, low coolant, loose connector, dirty air filter blah blah blah. Before you spend any money, spend some time just looking around in there.