Lady Silver

Hi all:
I would appreciate some ideas and guidance on an issue that just popped up yesterday. My car is a 2003 C4S coupe. Mileage is 51,000. When I acquired the car in 2021 with 41,000 on the clock I had the engine dropped and all the usual suspects updated with new (RMS, IMS, AOS, plugs, igniters, injectors, etc) The car runs perfectly. No issues at all. Except, yesterday I was driving along at around 60 MPH and the CEL suddenly lighted. Steady, no blinking.

Long story short, I took the car to my tech and he noted a P2096 fault on Bank 1 ageing delay on the oxygen sensors. He then found that the value was less than 1.2. He then checked voltages of both front and rear sensors on both banks and found they were "following" each other. I hope he was running the engine when these measurements were taken.

In any case, he is telling me I need to replace both the catalytic convertors, and all 4 oxygen sensors. This is an expensive proposition as we all know. It seems to me that 51,000 miles is low for failure of the Cats. I could certainly understand failure of one or more sensors, but not the cats.

He did reset the codes and the CEL light has been out since.

I appreciate your thoughts.
Thanks
Richard

Paul Waterloo

Replace all O2 sensors AND the CATS?

I would find a new mechanic.

996C438

I would find a long winding mountain road and drive her hard ! Get the cats and O2 sensors hot . It's good for you and the car . Then monitor results .

De Jeeper

O2 sensors do age and get lazy so replacing them is not a bad idea but u would hold off on the cats. Usually the cats will through an efficiancy code which is different. Sounds like the mechanic doesnt want to diagnose the issue ....he just wants to replace everything at your expense

gbarron

If the O2 sensors are original I would start with them. Cats can be an issue if they become poisoned by coolant or excessive hydrocarbons (oil consumption or running with misfires for extended periods of time) but without knowing the full history of your car it would be difficult to determine. As previously mentioned, try new O2 sensors then run the car hard to heat up the cats.

Lady Silver

Thank you. To me that sounds like a plan. I haven't seen the efficiency code. I hooked up my reader yesterday and no codes. So if I see the CEL again, I'll go for the sensors.

Lady Silver

It's hard to mind a tech with the depth of knowledge and experience on this board.

Lady Silver

Ok. That's my plan. Couple of rainy days here but over the weekend I will do as you suggest.

Lady Silver

The car uses a bit less than a quart every 1000 miles. I am running Mobil 1 0-40 Euro blend. The oil does stay very clean between changes, which I do every 3000 miles or 6 months, which ever comes first. Usually 6 months comes first. There is no smoke at all on start up or while running. It really does run beautifully.

De Jeeper

Fairly normal oil usage. I would just wait to see if the code pops again and go from there.

Lady Silver

Ok. I have run her about 200 miles in spirited fashion with all stops leading to at least 6500 RPM, after oil warms up at 3000 RPM, as I have always done anyway. 2 highway runs well over 100 MPH (very good radar detector and no cops anyway). No CELs shown. I should have mentioned I did a major engine out in December of 2001 at 41,000 including RMS, IMB, plugs, injectors, all the usual suspects. 51,000 on the speedometer now.

She is due for for an oil change late June so I will go to there driving in the spirited fashion as I am now. I'm thinking I haven't been doing enough of the spirited driving in any case. She seems to love it.

My tech has revised his position and now is thinking change out the sensors with the oil change visit, reason being they are original, 21 years old, and 50,000 miles +.

Basically wait and see as you suggested.
Thanks all for your help.
Richard

996C438

Before that next oil change add some fuel treatment . Chevron Techron or Seafoam or whatever flavor you like . Again run a tank or two HARD and then do the oil change . It is possible your O2 sensors are starting to age out . It's also possible they are good and just needed to get cleaned by getting the cats hot . Only time will tell .

De Jeeper

Changing them as preventative maintence and convience is not a bad thing. The issue u r having is with a rear o2 sensor. That sensor just determines if the cats r working. It does not have any effect on the engine and u will not harm anything by driving with that code. U can wait till the sensor actuallty fails in a consistant manor if u dont want to spend the money.

If it was a precat sensor i would change it asap. Those help the computer meter air and fuel.

Lady Silver

Thanks. Sounds like a good suggestion.