Looking for some advice. I have a 2003 996 with 120,000 miles on it. I replaced the sparkplugs and coil packs last year as part of my winter maintenance. While driving the CEL came on with no drop in performance, hesitation, misfiring etc. Scanned the car when I got home and got the P0420 bank 1 catalyst below efficiency. From previous vehicles I have owned this usually means the cat is not working at it optimum efficiency and thus sets off the emission code. I don't want to replace the cats just because its slightly less efficient.

Anyone have experience using O2 sensor spacers for the downstream cats? This I have hear can stop the CEL from popping up. In PA emissions testing is simply done by the mechanic hooking up the scanned and as long as there are no codes it will pass. There is no tailpipe test anymore here and certainly no smog testing.

Thanks in advance.

 

I have an x50996TT 2003 and I just got the same code, but when I put a different computer to it PWIS2 the error came up as tank vent not functioning during the ready test. I traced all hoses in the venting system and one was not seated. It had just come from the shop where they replaced the power steering tank which was rather close to the loose tube. I want to gather all of the specs for all of the vacuum tubing and just replace them all as they have hardened a bit making it tougher for them to seal.

I don't know if this is your problem but I found it uncanny to see someone else got the same code as I just did and it read different on separate computers