So I've got the oending sometimes full CEL P0411
Almost always I get a pending code even after resetting everything and occasionally I get a full CEL

I've tried replacing the smog/air pump and confirmed that it works but still getting the codes.

I've read that there are valves that control the flow but I'm not exactly sure where that's located.
Could someone point me in the direction to look and check if the valves are working correctly?

Thank you!

 

There was a thread with information provided by motorcarman a few months ago. You should be able to find it using the search.

 

Sorry, just found it.

Here it is for reference in case anyone needs it.
https://www.jaguarforums.com/forum/x...-p0411-149884/

 

Yeah, mine comes and goes too. It will light the CEL, then it will go out for a month or so, then come back. I used to clear it, but don't bother anymore.

So far I've been lucky enough that it stayed off long enough to pass inspection, but I'd like to make it go away permanently. I haven't really put any effort into it yet, such as changing the air pump.

Don't feel too bad though, my buddies with BMWs of this era apparently have the same problem.

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The check valves can fail, replacing that cured my CEL. It's a GM part on the normally aspirated cars, Chrysler on the XJR. You can get them on Rockauto.com quite cheaply.

I think the NA cars are a Standard AV7, AV51 on the XJR. Just match the thread and hose sizes give in the part info tab on rockauto. The Airtex valves are cheaper at the moment. As an application pick 1994 Ram 1500 5.9 for the XJR, 1996 Chev Impala with the 5.7 for the NA cars. Double check the dimensions before ordering as I am not 100% certain of the the thread sizes on the Jaguar.

The XJR valve has the pentastar on it and the Mopar part number.

As long as the pump works, I would look at changing the check valve before changing the pump.

 

Good advice, but a couple thoughts:

The pumps can appear to work by sound, but can be plugged with carbon and not pass enough volume. There isn't any way to know other than to test it and sometimes dump it out.

The valve can be very difficult to remove without damaging the air injection tubing as the tubing will often twist off when trying to uninstall the existing valve.


I already have a replacement valve, but have held off replacing it due to the concerns of breaking the air injection tubing.

I need to remove the hoses on the air pump too so I can test it.

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Always get in there with two wrenches. One to hold the pipe stationary, the other to unscrew the valve. Tight space on the NA, easy on the XJR.

 

I've got one ordered up on eBay which should be here within a few days.
I tried spraying some WD40 into the check valve to see if that would free anything up and make my pending CEL go away but after a few minutes it came back.

Which makes me wonder, when I started the car, it looked like the wd40 was burned by the exhaust since I had some smoke come out for a few seconds. If the check valve is stuck closed would it still let the wd40 through?

 

Any guidance on torque and technique when reinstalling the check valve? It comes with a crush washer, and would want it to seal properly but not over tighten.

 

I just did it up sung. Tight plus a grunt or two? I know, a highly technical torque spec.

 

Shouldn't. More likely the valve is rusted out and there is nothing there.

 

Installed the new check valve this morning but still getting the same pending CEL and got the CEL to actually come on once.
Still I can hear the air pump turn on when I first start the car

 

If you disconnect the hose going to the exhaust, is the air pump actually putting out air? There is a check valve inside the air pump housing that also rusts out.

 

Another thought, the ECU is looking for a response from the O2 sensors when the air pump comes on. Have you hooked up a code reader that can display the live datastream and see if your O2 sensors are responding? Maybe it's marginal O2 sensors that are not responding as they should?

 

So finally had some time to sit and stare at what makes up the secondary air injection...
After replacing the check valve and confirming that the air pump was indeed working... I was stumped as to what it could be since I was still getting the pending P0411 code and sometimes an actual check engine light code for P0411.
After a few minutes of trying to figure it out, I realized that when trying to custom fit my cold air intake, I rearranged my piping to get the intake curve as smooth as possible.
In turn I moved the pipe with the small bung that attaches the hose leading to the air pump much closer to the air intake intercooler and after the mass air flow sensor. Took everything apart and put the "bung pipe" right after the air filter and the mass air flow sensor closer to the intake intercooler. After doing so, I haven't gotten the pending code warning and after a round trip drive of about 10 miles, still no warning. Before after making adjustments and replacing parts, I'd still get the pending code either after 3 start ups or after driving down the street.

If you're getting this code/pending, I would double check the order of the intake elbows and mass air flow sensor. I haven't confirmed that I've fixed that issue but so far it looks like it's solved...
I'll update as time goes on if it comes back or not.