Code p0240 catalyst efficiency low. 2008 malibu LTZ with 3.6. enginen light has been on for several months, performance hasn't been effected, have cleared the code many times but come back within a da


Asked by Aug 15, 2014 at 12:01 PM about the 2008 Chevrolet Malibu LTZ

Question type: Maintenance & Repair

Initially I thought it could be the catalytic converter, but the performance hasn't been
affected at all. Is it possible to have a bad O2 sensor and still get this code?

7 Answers


It is possible but unlikely. Basically what triggers this code is the downstream oxygen sensor sees too much fluctuations in the exhaust gases leaving the catalytic converter. This tells the PCM (computer) that the catalytic converter is not "eating up" pollutants like it should. HTH. -Jim

3 of 3 people found this helpful.

What is your recommendation as how to fix the problem? Should I replace the down stream O2 sensor?

2 of 2 people found this helpful.

You can. But honestly I've never had an O2 sensor throw a converter code. It is possible though. HTH. -Jim

1 of 1 people found this helpful.

Ok, so I'm guessing that maybe you would recommend replacing the converter?

1 of 1 people found this helpful.

Yes, but you can check the wiring at the downstream oxygen sensor, just to be sure. You should also check your warranty booklet. Depending on where you are the converter may still be covered under new car emissions warranty. For example the converter on my '08 Grand Marquis is covered for 8 years or 80,000 miles from the date the car was originally sold. Even though I bought the car used, that coverage still applies. So you may be able to get a new converter free under warranty at your local Chevrolet Dealer. HTH. -Jim

2 of 2 people found this helpful.
Best Answer Mark helpful

Jim, Thank you for your help on this matter.

2 of 2 people found this helpful.

You're welcome, glad to help. Thank you for the best answer click. -Jim

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