2007 Aveo CEL Code P0420

[uncledad137]

I've got a 2007 Aveo with ~87,000 miles. For the past year I've been using this car for a ~100 mile round-trip commute for work most days of the week.

The check engine light came on, took it to my local mechanic and it presents code P0420. They say air fuel ratio sensor and oxygen sensor are working good and recommend replacing the catalytic converter. They also found the coolant reservoir has a pinhole leak, engine air filter is dirty, air intake hose is broken, and the drive belt is cracking. Probably like $1500-$2000 to repair everything.

This car has given me a number of problems recently including a bad wheel bearing, cracked aux serpentine belt, flex hose exhaust leak, etc. I also got the drive belt replaced within the last 2 years, surprised to see it cracked again. Repairs are starting to really add up.

$87k miles does not seem like a lot to me, but is it time to let this car die and move on to something else? I really need a reliable commuter car that's not going to give me problems every couple months. Just looking for some opinions.

[avguy]

That quote is off the charts high. Can't understand how they can say the downstream O2 sensors is 'working good'. The P0420 is set because of an out-of-spec voltage from that sensor, so how could they possibly know that it's ok, without pulling and testing it in another vehicle?
In fact, a fairly typical approach is to replace the downstream sensor (and maybe the upstream as well) on a P0420, before doing anything else. Did they run any testing on the cat itself, in order to back up their 'diagnosis'? Also, did you ever have a bad misfire for any length of time with this vehicle?
IMO, this outfit sounds like crooks, and I recommend that you take it to another shop for a second opinion.

[uncledad137]

A couple of years ago, I did have a period of time with bad misfires - my understanding is there was oil leaking onto the spark plugs preventing them from firing. The engine would shake. It was diagnosed and repaired at a Chevrolet dealer. No problems with misfires since that and have probably put another 20k miles on the engine.

I don't know exactly what they did to assess the sensors. On the report they gave me, there's 2 printouts from a computer program which is displaying "Oxygen sensor output voltage and associated short term fuel trim"

Page 1:
Sensor #1 Output Voltage: 0.750V Short term fuel trim: -001.6%
Sensor #2 Output Voltage: 0.780V Short term fuel trim: 099.2%

Page 2:
Sensor #1 Output Voltage: 0.125V Short term fuel trim: 000.0%
Sensor #2 Output Voltage: 0.780V Short term fuel trim: 099.2%

This is a local shop which has pretty good reviews on Yelp but they do sometimes seem pricey. Just for the cat replacement it would be $1100. I'll try to get a second opinion.

[EAD15]

That quote is off the charts high. Can't understand how they can say the downstream O2 sensors is 'working good'. The P0420 is set because of an out-of-spec voltage from that sensor, so how could they possibly know that it's ok, without pulling and testing it in another vehicle?
In fact, a fairly typical approach is to replace the downstream sensor (and maybe the upstream as well) on a P0420, before doing anything else. Did they run any testing on the cat itself, in order to back up their 'diagnosis'? Also, did you ever have a bad misfire for any length of time with this vehicle?
IMO, this outfit sounds like crooks, and I recommend that you take it to another shop for a second opinion.

Considering it would have to be a CARB legal cat (OEM most likely, and has to be new. Thanks California!), I would say that price seems fairly standard by the time you factor in parts and labor on the other repair items as well. If that's what it needs

Edit: However, I would agree about seeking a second opinion and trying the o2 sensor first.

[2010AveoLT]

Considering it would have to be a CARB legal cat (OEM most likely, and has to be new. Thanks California!), I would say that price seems fairly standard by the time you factor in parts and labor on the other repair items as well. If that's what it needs

Edit: However, I would agree about seeking a second opinion and trying the o2 sensor first.

just be glad you don't have an 09+ car; the OP would have been staring down the barrel of a $3,000-$4,000 bill, because the cats for an LXV engine are still EXTREMELY expensive even after 6-8 years of being off the market!

[avguy]

Considering it would have to be a CARB legal cat (OEM most likely, and has to be new. Thanks California!), I would say that price seems fairly standard by the time you factor in parts and labor on the other repair items as well. If that's what it needs ....

From reading just the OP, my first issue was the wide range (i.e. $500) for a specific list of items to be repaired. I interpreted that to mean they were likely to bill 2K, which IMO is way too much. But with the followup post, indicating $1100 for only the cat, that again appears to be sky high.

I'm basing that on the shop being able to buy a cat wholesale for around $350, similar to the link below. AFA the labor, I'm assuming no rusted front pipe-to-cat bolts, as we always get here in the rust belt. So this job in CA is likely to consist of spinning off 6 bolts, swapping the new cat in, and torquing the 6 bolts back on. That would be around 1/2 hour or so total time. Worst case (i.e. one or more frozen bolts), might require cutting the cat off the flange. Let's say that would take 2 hours x $150/hr = $300 labor. Even that last scenario is far less than the $1100 quote.

But I'll freely admit that all of this is JMHO, from a DIY perspective, and perhaps I'm just unaware of what (honest) shops are charging these days.

https://www.catalyticconvertersonlin...te=2&year=2007

[uncledad137]

Pretty frustrated with this shop! Out of their laundry list of problems, the only one that really seems to exist was a broken air intake hose. Bought one online and replaced it myself. Used an ODB reader to clear the P0420 code a couple of days ago and it hasn't come back on. The O2 sensor readings on the freeze frame which triggered the CEL were way off what it was reading while running - maybe just a glitch? Regardless even if the cat needs replacing I can buy one online and replace it myself for *way* cheaper. Just really feels like they were trying to swindle me into expensive repairs.