Hey all:
I had the typical problem of the engine-light coming-on when it was very cold outside. It would come on in the morning, and typically by the afternoon when it would warm-up, it would go back out.
I didn;t worry too much, as this seemed to be common.

Now it's on and doesn't go off.
Can anyone tell me how frequently the parameters are 'sampled', and how long a code should stay active? I don't know whether I've got a real problem here or not.

Is there a way to manually reset it, so I can see if it comes back on?

Any other ?? and answers would be appreciated.

thanks!

 

You may unplug your neg battery cable for 15 mins and hook it up to reset the code but the best solution is to check the codes thru a code reader and see what it throws up
Other than that if there is nothing serious , after a few successfully circling the key , start the engine if PCM don't get any bad signals , the fault light should go off on its own

 

THANKS CADILLAC!

so, I was over at my dealer, and had him pull the code for me. "PO420, Catalyst Inefficiency"
He reset it for me, but I'm guessing it'll come back.

He tells me that's one of two things: either an old cat-con, OR a bad o-2 sensor.
"How do I know which?" I asked him.
"$129 to put it on the machine and find out", he says.

Does this sound like that old deal-e-o with the o-rings in the intake manifold / rocker cover breather pipe, as seen in the FAQ's here? https://www.jaguarforums.com/m_85477/tm.htm

 

I have the same code showing on Bank 2. I was into the dealer for a service and they did the J004 upgrade, did a reset and figured it would be OK. It isn't. I will be back to the dealer in the next week or so and they will fix the problem so once they do I'll post back for you on what they found. As I understand it the basic deal with that code is if thereadingsfrom the O2 sensor pre-catalytic convertor are"too similar" to the ones post-catalytic convertor (or vice-versa)it will set the code.

 

HMM. VERY INTERSTING.
let us know what you find!

 

If you have the efficiency code there are more than 2 possibilities. Consistent misfire can foul the cat and cause reduced efficiency. You didn't mention any other codes that may have been found though and misfire will always leave a code even if the miss goes away. Fuel with either high alcohol or sulfur content can also foul the cat and cause reduced efficiency and you would never know it from o2 readings. Unless I can hear broken pieces of the catalyst rattling around on a test drive(very bad cat) or find codes that could help contribute to the efficiency code I usually do the following blow out test drive. Get the car to normal operating temp, find either a hilly(not likely where I am) road or take the car on the highway. Put the j-gate in either 4 or 3 depending on just how fast and clear the road is so that the engine is revving in the 3500-4500 rpm range under HEAVY LOAD for at least 5 miles. This will cook the cat and clean out any junk that may be in the catalyst honeycomb. If this stops the CEL you are good to go, if not, exactly how many miles are on your car? The catalysts are covered by the federal emmission warranty 8 years 80k miles which ever comes first.

 

sorry, Real_Tech, I should've stated the deets.
Mine is an '02 2.5 w/ 5-spd MT. 113k miles.
So yes, the cat could be gone (though the exhaust looks recent, and I've only owned the car since 106K) but I suspect that's not it. I will absolutely try your blow-out method though.
No other codes flashing. But it is seems clear that there is a temperature component to this. Certainly it could be temperature affecting combustion and / or catalization.... but... maybe it's just wishful thinking... but it seems more simple than that, as it's been like a light-switch for 2 months.
I've driven just over 100 miles (in just over an hour ) since the dealer reset it today, and it has not come on again. But I can almost guarantee that tomorrow morning, when it's 16f outside, it will be back on immediately (I mean before-I-take-my-hand-off-the-key immediately).

 

cats need to come up to temp to clean exhaust, and if your seeing it when cold only I wouldnt worry about it....especially since theyre not easily replaced or subsituted with aftermarket universal cats...but remember O2s are like spark plugs and for optimum efficiency need to be changed, how often is up for debate

 

the light is back on this morning, just as expected. 20f outside when I started it up.

I've never heard this before.
Can they be cleaned? What should I expect to pay for 'em at my dealer? (I've been burned before with aftermarket O2's. )

 

Run a can of BG 44K with a full tank of gas every 2000 miles for a couple times a year..You won't have to worry about O2 sensors or plugged Cats