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Cel Low Cat Efficiencey Bank 1?

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Ok so I picked up my 98 Boxster with 70000 miles on it this saturday. Sunday I'm driving my new toy, and I get a CEL. Being a part time Autozone Employee. The first thing I do is pull into the store, and hook up the old OBD II. 1 code. "Low Cat efficiency, Bank 1" Past experience tells me it's probably an O2 sensor. 2 questions.

1) Assuming the dealer who sold me the car won't step up, and I have to fix it myself, Where would this O2 sensor be, and

2) Is this a common issue with these cars? so should I replace them all? (I believe there are 4 in all)

I have access to a lift, would this be a difficult repair?

The car runs great! and there don't seem to be any adverse effects YET.

You help will be greatly appreciated!


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That fault could mean that your cat is on the way out. Your DME compares the readings from your o2 sensor before the cat and the o2 sensor after the cat to make sure the cat is working properly. If the the readings dont vary enough then it will set a fault.

Does the car have an aftermarket exhaust on it? My car (04 Subaru WRX) has a catless aftermarket exhaust on it and I get this CEL because the lack of cats makes the rear o2 sensor freak out because its not seeing any change from the readings of the front o2 sensor. The CEL could have been cleared before it was sold to you and has just now popped back up.

Edited by PTEC
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Thanks for the input!

the car has a stock exhaust on it, so I dont think that's not the cause. I'll contact the dealer today!

Also. for your WRX. I work for a Subaru dealer.... AND a Subaru performance company. (M.S.P.T. metric subaru performance tuning) and we do have a CEL fix for your car! check it out on www.mspt.net (shameless plug!)

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Just an update. I contacted a local Porsche dealer, and after running my VIN, he informed me that if he could confirm the cat is defective, Porsche will replace it under warranty!!!!


by the way it's a 98 with 70800 miles on it.

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