On a recent trip my ETS lamp came on while I was 250 miles from home. I couldn't stop so I just kept cruising and monitoring performance. There were no noticeable performance changes and I made it home fine. However, I did notice a unknown smell when I was stopped and could get a whiff of the car. When I got home I opened it up and sniff tested all over without being able to locate the smell. It seemed rearward and not related to the brakes. The ETS lamp turned off when I started the car the next day but came back on when my wife drove it around town. I pulled the code and it is P0422. After pulling the code, the lamp turned off again. I have had rear O2 sensor codes previously with the CEL but it went away when I started using premium gasoline.

All of this leads me to consider Catalytic Converter replacement as a fix for my problem. Is there any chance I might need to do something else instead? I'd hate to spend the money up front if it isn't the root cause. Any comments are appreciated.

Thanks!
-sven

Full Disclosure:
My cruise control also became intermittent on this trip after stops and I plan to replace the cruise control cut out switch before looking for more faults there.

P.s. - I have noticed/suspected decreased fuel mileage over the past couple years. It has been so slow though that I can't be sure.

 

Check for vacuum leaks and make sure the front O2 sensor is in good condition. Also make sure the rear one is working as it should.

 

Thanks for the reply!

Without any current trouble codes, is it safe to assume they are in proper working order? Or are you just recommending visual inspection while I have the CAT out?

Speaking of O2 sensors, I picked one up from FCP Groton a while back but I couldn't reach the front sensor to replace it. What is your standard technique for replacement if you aren't planning to replace other parts? Is there something I need to remove to gain better access? This is really for future reference since it seems I probably need to replace the CAT right now anyway...

 

They might not be good. It just might not see the fault at this moment.

The Cats rarely go bad. It is usually O2 sensors that are bad.

 

It turns out that some of my symptoms are related and others are not.

I have learned that my car is throwing DTC ECM-9400 (Brake pedal sensor - Signal too high). The brake pedal sensor problems can cause both cruise control failure and the ETS lamp as symptoms. I will replace it and anticipate solving these problems.

When I had my car in the shop for an oil change (I let the Volvo shop do the oil changes because they are always checking for stuff like the following) they noted that the angle gear had leaked most of the oil and needed to be monitored to see if regular topping or resealing was needed. Upon further review by me it seems the smell I was noticing is most likely the lubricant leaking from the angle gear box. That's exactly what it smells like (i.e. burnt lube) and definitely comes from that location (i.e. under center) only when the car has been driven a while. Unfortunately, I just had the propeller shaft replaced in January and the failure of the previous shaft may have been the cause of the angle gear seal failure. Oh well.