I know there are a lot of posts regarding catalytic converters but here’s another one.
My mother bought a 2001 Volvo V70, turbo, from a private party. About two weeks after she bought it, the check engine light came on. She took it to an independent mechanic and they said the code was P0422 and that meant the catalytic converter needed to be replaced at a cost of $1400. She did not have the repair done at that time. The car has 113,000 miles on it so it does not qualify for the emissions warranty.
We reviewed the repair records and discovered that the previous owner took it to the Volvo dealer with the CEL on at 105,000 miles and got a return code of ECM 4801. Apparently that means ‘replace the catalytic converter’ too. The dealership turned off the CEL and I can only assume the car went 8000 miles before turning the CEL on again after my mother bought it. She took the car to the Volvo dealer and they said since we didn’t have emissions inspections in our area that they would just turn the CEL off. They did turn it off and it has not come back on (though she’s driven less than 100 miles since then). She asked both the independent mechanic and the Volvo service writer if they should try replacing the oxygen sensors first and they both said why would you want to do that if they’re working? (though they gave no evidence that they had determined they WERE working). As far as I know, the car is still running fine. She does not want to replace the catalytic converter unless it really needs to be replaced.
I have many many questions but the ones I would like to post here are:
1. If the catalytic converter really does need to be replaced, why doesn’t the CEL come back on immediately after being turned off?
2. Is she doing any long-term damage to the car by continuing to drive it without replacing the catalytic converter?
3. Is there any definitive way to determine if the catalytic converter needs to be replaced?
There is no code that says, “replace catalytic converter.” That’s BOGUS, no matter who says it to you.
A code, or several codes, may indicate the cat is not working correctly, but there may be simple reasons for this, such as O2 sensors sending incorrect signals to the computer. I’d try new O2 sensors, especially considering the mileage, before spending a lot of money for a cat you may not need.
Mom’s not going to damage the engine by driving this way. I’d ask to see the EXACT wording of the code, then tell them to replace the O2 sensors, then cross my fingers. Many catalytic converters last 200K miles or more. It would be a shame to waste money replacing one that is OK.
Besides, if it turns out she really does need a new cat, she’ll want new O2 sensors anyway, to keep the cat working the way it should, and the engine running correctly.
Question 1. Software related (not a “glitch” but how it’s written)
Question 2. You can have the car “sniffed” to get a idea of cat efficiency and you can test engine manifold vacuum and get a idea if the cat is restrictive.
Question 3. (You did not ask)The 02 sensors can be “scoped” and their waveform analyzed to determine how well they are working.
If the catalytic converter really does need to be replaced, why doesn’t the CEL come back on immediately after being turned off?
The light is triggered by a sensor indicating a possible problem. It likely needs time and maybe specific driving conditions to make that measurement so the delay.
Is she doing any long-term damage to the car by continuing to drive it without replacing the catalytic converter?
Maybe. Depending on the reason that light is coming on and what the sensor is sensing, it could be something wrong that will damage the converter and or sensors. With out knowing was it wrong any response is just a guess.
Is there any definitive way to determine if the catalytic converter needs to be replaced?
Yes, but it is not one YOU can do. In any case before you even make the decision to do further testing, lets get the results from the built in testing system the CEL.
There is something within the engine which needs repair. Some of the things that can negatively affect the catalytic converter are: an engine burning oil, or anti-freeze, or too much fuel (rich), or too little fuel (lean).
The shops aren’t now trying to change parts; but, neither are they trying to fix the problems. Checking for the engine “bad diet” items are a start.