Check engine light

mazda
engines
lights
millenia

#1

I have a check engine light pop up again.

I had repairs last year for this with a major tune up (brakes/spark plugs/NDK wire replaced) for $1200.

The new codes that came up are P1170-H02S11 and P1173-H02S21. What does this mean and what do I need to get this fixed? Is is worth getting it fixed or just selling the car if possible.


#2

It would help to know the age and mileage of the car, and what other work needs to be done. Brakes and spark plugs are ordinary wear and tear items depending on when it was done.


#3

The codes point to failed oxygen sensors on bank one and bank two…These sensors cost about $80-$100 each and may require some labor to install them. They screw into the exhaust pipes and control the fuel mixture…


#4

I had repairs last year for this

You may have had repairs last year for something. But the check engine light isn’t a “this” - there are lots and lots of things going on in the car’s systems and different things can go wrong - hundreds of reasons the engine light might turn on.

Contrary to Caddyman’s assessment these codes might indicate bad O2 sensors. But 2 going out at the same time? Its possible, but its not the first thing I’d suspect. The O2 sensors are likely the “messengers” - you can shoot them if you like but I’ll be it will be a waste of money.

Basically, just about any code that mentions what an O2 sensor is doing can come from a bad O2 sensor; a problem with O2 sensor wiring; completely different problems that throw off the fuel / air mix (in which case the O2 sensor is just doing its job). Given that you simultaneously have codes for both banks I’m going for fuel / air mix.

Someone should check your fuel system (pressure, regulator, injectors) and check for vacuum leaks to start with.

You didn’t give a year. But I’m going to guess that you’re not 12 years old and maybe the “1998” after “cargirl” means that the car is a '98. If that’s right then you have a 13 year old car. Expect to have to put money into it on a fairly regular basis. Keep watch on things and when that money becomes more than a regular car payment plus higher insurance premiums plus higher taxes if applicable, then you think about getting rid of it.

And those “repairs” last year were not “repairs” - they were maintenance. Any other car you get will also need brakes and spark plugs at some point. These are normal wear and tear items.

One more point. Sometime last year you got a check engine light. Nothing about your brakes would cause this. So I’ll make some more guesses. Your CEL came on because of misfires. The misfires were caused by having old spark plugs and wires. The only guess I can make about that is that you don’t pay attention to the car’s regular maintenance needs. This is penny wise a pound foolish. Spend a little bit as you go to keep the car up on repairs & maintenance and it will actually save you money in the long run.

I apologize in advance if any of my guesses are wrong.


#5

Thank you for the help. The items done last year were for the 60K maintenance (was at 55000 miles then). The mechanic had said this was the cause of the check engine light and fixed all of that and it went away.

Its a 1998 Mazda Millenia. There haven’t been any other major repairs. At this point, they wanted to replace two of the sensors to see if that fixes the problem but they’re not sure if that will work. They also said they’ll try one in the front and back on the right side based on the codes in a few hours. They didn’t look at the car just ran the codes and told me this info. They also want to do an intake cleaning but I thin that was done last year on the 60K maintenance visit. Does it sound reasonable to pursue this repair? What is a reasonable fee to resolve this issue?


#6

It’s probably reasonable to pursue a repair on a car with only 60K miles (unless you live in Vermont and drive through salt 6 months out of the year and the body is falling apart) but this shop might not be the best place to have it done. I get the feeling they are just throwing parts at the problem and are not interested in doing a proper diagnosis. Ask them if the sensors do not fix the problem, and are actually sensing a bigger problem somewhere else, will they refund you the cost of the unneeded repair.


#7

Thank you for the advice. I went to two places and both siad “no need to look at the car” and just did the scan and told me the same thing.

Will ask for the guarantee or refund if it doesn’t work.

Also, if the sensor ends up being the issue, how much should something like that cost? I got two very different estimates…


#8

I checked my favorite site for parts, one is 41.79 (post cat) Pre Cat is 55.79. so anything over 250 is nuts. A lot of muffler shops will do o2 sensors for a good price. o2 sensors tend to get stuck and need a torch to be pulled out. Muffler shops generally have good tig welders that they can get the sensor even hotter with and pop out the most stuck sensor with ease. A lot of muffler shops will also let you supply the part…saving you lots of money


#9

But listen to cigroller…IT’S PROBABLY NOT THE SENSORS!!! They are only the messenger. something is wrong upstream, do what Cig said first…


#10

So I went to a mechanic who took a look at it (cost about 100$) to estimate what’s wrong. They said the Battery needs to be replaced and the posts/cables need replacing since they were corroded this would cost me $230. They also said the EGR needs to be cleaned which is $80 and possible another $20-80 if they replace the part. They also said the PCV valve needs cleaning $40 and then it’d be $8 to replace it. They then said the codes would be rerun and they’d let me know if anything else needs to be done. Somehow after all this the check engine light disappeared again.