how can we test to see if this is electrical and not valve or vacuum issue?

 

Note: it's P0414 (assuming you got the digits right).

With that, you can Search for others and what they did.

Your car is late enough that it may have SAIR (secondary air).

 

Yes It's a PO414 code. We smelled something and a few min later the engine light came on. Code Reader indicated the PO414. I have been digging thru threads but haven't uncovered anything for this model, only for the XJ8. Are they similiar enough to troubleshoot the same. That guy said to download workshop manuals and pg 1942 would show you how to do a pin test on a certain pin. But the manual he referenced and supplied is for the XJ8. Is this advisable for my S Type? Thanks !!! Its our first Jag, and we love it.

 

It's a zero not an oh.

 

Well no engine listed so that is a mystery?

It looks like you could have a wire harness problem behind the front bumper. The wire loom rubs and then caused all kinds of weird errors. I would drop the front bumper cover which is pretty easy and take a look at the wire bundles.

Plus your car is a bit unusual because the secondary air was only added on the 2005-2006 and up cars. So I think you must have a 6 cylinder?
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It's a 4.2L V8 with only 95,000 miles. We just had the radiator flushed before a 5000 mile trip, so it's possible they accidentally bumped or could have caused the wiring harness to come loose if it is close enough. Where is it located?

 

When you remove the bumper cover the harness will be in plain sight.

Just carefully inspect it and be aware that this same wire loom runs above the wheel wells too and those area's have caused problems in the past.
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I wonder if it would be easier to figure out other causes, as the bumper is a pain to deal with - as is the harness.

There's a PDF version of the workshop manual - it may be newer i.e. include SAIR items. Or there's the proper jag TOPIX (non-free).