It depends. What did it fail on? High HC could very well be oxygen sensors, since they have a finite life. Usually after about 60,000 miles they are ready for replacement. They don't fail all of a sudden, but gradually read leaner than the actual value. This causes the computer to put in more fuel resulting in higher HC and worse fuel economy. They can get pretty bad before they set off the CEL.

OTOH, NOx is usually from a fault in the EGR system. CO is often cats but can be other things too.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.