2001 s40 Recurring Check Engine Light
 

Hey,

I have a 2001 s40 that I have been driving for the last two years with minimal problems. Recently I got a check engine light and noticed the car was not running that well - idle at really low RPM, poor pick up. I took it to the mechanic, he read a p0172 and decided to change the engine thermostat. I drove the car for about ten miles and the check engine light returned, this time it read a p0101. The mechanic told me I could continue to drive it for a couple days before bringing it back to him. As I drove the car the check engine light would go away for a bit and then come back, this cycle continued a couple times. After having the mechanic take a look at it again he said he needed to clean the MAF and everything should be fine. I drove it out of the mechanics shop and the acceleration was much better. Five miles down the road I got the check engine light again decided to take it back to the mechanic. On the way back, the car stalled and I had to restart it at a red light. The mechanic pulled the code reading p0163, he said to drive it for a few days and see what happened. Anyone have any clue what may be going on here or what needs to be changed or looked at? I have a smog check for renewal coming up so I need to figure out what is going on here.

I greatly appreciate any help/advice you guys might have.

Thanks!

P0163 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 3)

Have you been getting really crappy fuel mileage?

yea I have - the fuel mileage has been bad every since I got the car, though I will say worse lately - I just assumed that was how the car ran

Any ideas on what I should change/take a look at???

Thanks!

I got the P0101 several days ago, according to the suggestion from a professional, check the air filter is the 1st step, and clean the MAP filter is the 2nd step.

How bad?

P0101 is related to MAF signal. Theoretically you could have gotten oil on it if you just re-oiled an air filter. Best to clean it: there is a link to a how-to in my sticky FAQ thread.


I think your problem is with your O2 sensor. Code P0172 is for long term fuel trim (rich). That could all be caused by a bad O2 sensor. In fact it probably is.

Have your mechanic replace: Bank 2 Sensor 3 O2 sensor and reevaluate. Shouldn't be too expensive.

13-14 mpg (i drive short distances at relatively low speeds)

lately I would say its dropped 3 or 4 mpg

How much do you think it would be to make sure I am not getting over charged? I have already sunk a few hundred into this issue.

Do you think it could be a combination of a faulty O2 valve and dirty MAF? After the mechanic cleaned it the car has been running much better (minus when it stalled at the light)

Thanks for taking out the time to help! It is truly appreciated!

Did the mechanic already clean the MAF?

That's REALLY bad mileage. Mine is low at 20.6, but I have cold air intake and 17 inch rims.

O2 sensors I believe are around $150 + labor.
That's just an estimate, I've never had to replace one before.
I think that should take care of the problem though. Run it past your mechanic in any case.

Yea he cleaned the MAF and also replaced the thermostat. I had asked if it was possible to have an air leak - he said he checked and found nothing.

He recommended I drive the car around for a few days and then bring it back so he can take some readings, also wanted to see if the CEL goes away and then comes back again or not.

I am thinking of taking it back Thurs or Fri and I will talk to him about the O2 sensor to see what his thoughts are on that, hopefully that solves the problem!

What about the air filter? Do you think I should change that as well? I am assuming he looked at it, but I didn't specifically ask and he didn't mention anything about it

No, don't worry about the air filter if it's not absurdly dirty.

The CEL may turn off, but that doesn't mean the underlying problem is gone.

I dropped it back off with the mechanic today and he said that he doesn't think it is an O2 sensor but thinks there is a problem with the "O2 turbo boost" He says he is going to drive the car around with the computer plugged in and take some readings.

Frustrated with the situation, I asked him today if I should just take it to the Volvo dealer and he said, "I haven't given up on it just yet"

What are your thoughts on this?

What?
O2 turbo boost?
I've never heard that before. Does this mechanic specialize in european?

No he doesn't, which is why I am getting a little wary. He is going to drive it around with another computer plugged in today and then tell me what he thinks. After that I will decide if I want to stick with him or just bite the bullet and take it to the dealer.

For some reason his OBD machine reads the P0163 code but doesn't give the same description about the O2 sensor that I found online.

P0163 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 3)

OK, he's wrong then because this is directly off VADIS (volvo troubleshooting software)
You need a new mechanic. An O2 sensor should fix the whole problem.
He's stringing you along, charging you for hours of labor when the answer is obvious.

Called me earlier today and said that the problem is a faulty MAP sensor not an O2 sensor. Does that sound like it could be the problem?

He is only charging me for parts, so no labor or diagnostic fees.

Thanks for your help!

Seems to me if the O2 sensor is throwing the code low voltage that should be the issue then. The MAP sensor is not throwing the codes.

I don't know anything else about the MAP sensor.

I say take it to a dealership or euro specialization place and get a second opinion.

I get a CEL occasionally and the code reads P0101. I have replaced the MAF and the problem still occurs but less frequently. When the CEL does come on, it always occurs under the same conditions: idling down hill at about 50mph (foot off the gas) and the CEL comes on. Several days later, I'll start the car and the CEL is off.

This sequence repeats itself every 7 - 10 days. No real driveability issues other than the acceleration seems sluggish sometimes. Fuel economy = 26 mpg.

Someone else suggested changing the O2 sensor. The manual shows 2 on this car: one before the turbo & one after. One is heated, the other not (not sure which is which). The O2 sensors are about $100 ea (Bosch).

I don't want to just blindly change parts but if this is the most likely next problem, not too much cost or labor involved.

I tried everything I could to find an intake leak and could not.

Any other suggestions?

Thanks.

Thanks for the info, I appreciate it.