Hi all, new boy with 'Check Engine' caption query

[KJMcK]

Hi forum members. I'm a long time Jaguar enthusiast and driver and have recently purchased a 1997 X8 4.0l with 85,000 miles recorded and lpg conversion. I will endeavour to provide a more full report on the aquisition at a later date. My present query (and reason for my first foray into the unknown world of an online forum) is regarding the 'Check Engine' caption. I didn't notice this item in the excitement of the purchase 3 days ago! Each time I switch on the ignition before starting the engine, after the initial sequence of warning lights going out, as well as the 'oil can' symbol, my 'Check Engine' caption remains on. They both then extinguish when I start the engine. Is this normal, or does it indicate a problem?

[daveji]

Hello and welcome to the Forum
The orange "check engine" indicator is activated by the ECU after analysis of signals from the Lamda sensors on the catalytic converters.
They check the emissions from the exhaust and the ECU uses this information,together with info from other scources to control the fuel mixtures.
The "check engine" light comes during the electronic system self test sequence as you describe, but it will not extinguish until the sensors and the ECU have some exhaust gas to work on....when the engine is running.
If all is well the warning light will then go off.
The red oil can symbol is the low oil pressure indication,if it goes off quickly as the engine fires up all is well there too.

[KJMcK]

Thanks Dave for taking the time to reply. That's a great relief. I don't know where I got the idea that the caption should go out after the initial check sequence.....must be from some other dashboard in the past!

[dougallen]

Would anybody know what the fault may be if the engine check symbol fails to extinguish after the car has started and remains on while runing although no other message is displayed

[daveji]

Hi Doug
When my XJ8 did this the warning light had to be cancelled with the Jaguar computer (IDS/WDS) at my Jag Specialist.
They advised it was probably due to short journeys resulting in the CATS not getting hot eneugh......so give the car a regular blast up the dual carriageway to get the exhaust nice and hot !......If this was done the problem likely as not would not return.
That was five years ago....and it hasn't !
They also said they have a couple of cars on the books that need this alarm reset about once a year.
If you have a reset done and the alarm reappears again quickly it indicates a downstream Lamda sensor is faulty......the diagnostic computer will isolate the problem.

Dave

[dougallen]

Thanks Dave

Will get the car to the dealer for a reset. It's likely to be as you say. I use the car very sparingly - weekends mainly and just a few short journeys so will give it a blast


Doug

[daveji]

May I suggest a good blast first......then a reset........I too use my XJ8 sparingly now....but
following advice I take care to warm it up well when I do use it.....10 miles minimum for exercise...even if it means deliberately going "the long way round".
good luck......and enjoy
David

[dougallen]

Hi

After a few weeks of intermittent display of the message but no diminished performance I had a diagnostic check. Turned out to be the knock sensor that seemed to have a bad connection. Cleaned it up and refitted. Running ok but will probably replace the sensor when next due for service.

Thanks for your help

[dougallen]

Just to round this off. Engine light returned and had further check. Downstream lambda sensor found to be faulty. Jaguar price was £384 for the part. Managed to pick new sensor up from ebay for £120. Now fitted and running fine (might invest in code scanner/reader for about £30)


Doug