Management light - '05 S Type

70sammo

Hi all. Ive just joined so be gentle...lol
I have a 2005 (55) s type r 4.2 and the problem i have is that i have a constant amber management light on.
A diognostic test has said that bank one cat below threshold. There have been a couple of times that the light has gone off by itself and stayed off for a couple of days.
This has been for 4 years now and even a main dealer couldn't find out why, The car has passed every M.O.T. and emmisions tests and drives fine.
Any help from you guys would be greatly appreciated as i would like to sell the car soon.
Many thanks

mrfitix

70 sammo: Do you live in a cold climate?Jag's have very sensitive O2 sensors.that if the heater in the o2 doesen't get it hot enough quick enough OR the cat. has had to much fuel for a extended time it ( the EMC)will think it's slow. This will be the FRONT bank 1 which closest to the motor.The front two O2's regulate the fuel ratio and the back two are there to TRIM the front two, Trim, as in adjust the parameters high and low of what the front to should work at.On a scan tool the readings for the #1 O2's should be moving up and down to compensate (lengthening and shortening the pulse duration of the fuel injectors) the rear two watch the front two and the reading should be very minimal movement. So what has happened is the bank # 1 cat is weak and probably Kicking a P0420/ P1420 for inefficiency. Your Jag probably kicks a code just before it gets fully warm then after you drive a while it

mrfitix

goes out only to come on again if you accelerate or stop at a lite because the O2 can't react fast enough HENCE the lazy/slow code.Could be as simple as a broken wire to the heater on the O2, Have you had and vacuum leaks

mrfitix

fixed lately? Do you overfill the gas tank regularly?Had any injectors replaced? All can cause O2 to fail.

70sammo

Hi Mrfitix, thanks for replying. I live on the southcoast of England, so not really cold, apart from winter. i do remember that on the few occasions that the light has gone out, it was on really warm days in the summer, but two or three days, once even a week later, it comes back on and stays on, and even then , it came on after being driven for ten minutes or so. I think maybe i might overfill the tank to round up the price as i commute 70 miles a day round trip to work, that will stop now, although probably too late i guess. I haven't had any injectors replaced, just the spark plugs on a service, also one of the o2 (lambda sensors) which was reading erratic. I'm not aware of any vacuum leaks. I will ask my local garage if they can replace (if needed) the wire to the heater. i will try to stay away from main dealers as they are way to expensive, used them on the one occasion £100 per hour plus parts.
I hope i have shed a bit more light on this for you, as i'm not really mechanically minded, any further hints/tips would be great.
Thanks again for the reply, much appreciated.