persistent check engine issue

[beerlover]

I know this is a bit random but just wondering if anyone else has dealt with this.  My check engine light keeps coming on in my '06 Toyota. I do expect this stuff to happen with an old car. However, I have replaced 3 parts on it already in the last 6 months that were supposedly causing it (O2 sensor & spark plugs the 1st time, mass airflow sensor the 2nd time) and it has come on yet a 3rd time. Is the check engine light just a scam to cost me money every few months and make me angry (it's working), or should I actually be concerned? Has anyone ever dealt with something like this and finally got the issue diagnosed correctly? I'm a little irritated that I'm out $400+ for those other parts and it may not have even been that to begin with.

[carmenere]

Have you checked that your gas cap is on tight? That was a constant issue with my last car.

[beerlover]

carmenere, it is. I did think to check that already ha.

[winecat]

Where are you taking it to get the code read? An auto parts store should be able to read the code for you so you'll know what it needs before going to a mechanic. It might be something simple that you can DIY.

[Leeham Rimes]

This happened to me in a 2011 Dodge Caravan. I dealt with check engine light issues for two years. no one could ever figure it out. eventually, in between check engine light issues, I traded the stupid thing in. I ended up spending probably at least $4000 on things that needed to be “repaired “ this experience turned me off from ever buying a used car. It was the only car I ever bought used and the only car I’ve had nothing but problems with. Another problem I had is that the car would sometimes just not start. No reasons, I replaced tons of stuff. Nothing ever worked. I took it to three different mechanics and every one of them was so confused and had No idea why it was constantly triggered. One place kept my car for about a month trying to duplicate the issue. They claimed they couldn’t. The day I got it back, it wouldn’t start and the check engine light was on.

I got so bad to where I had panic attacks every time that stupid light came on. Sorry you’re dealing with this.

[keegmiles]

I had a 2000 Toyota Avalon that had the same problem. The code reader was spitting out a generic code, but I was also having performance issues with the car. It was a rarely known part that was causing issues. It took about a month of trial and error because of the generic codes. I know how frustrating it is!

[agnes]

A check engine light can come on for various reasons.

With my 2013 fiat it has come on through the years. Usually H will bring a computer from work to read the code to see if he should fix himself. the first big issue in 2017 it went on they basically had to replace the computer in it. I had a rental for a whole month. This was all covered under warranty though. The second time this past summer, was related to emissions. It was out of warranty by this point and cost around 600.

[beerlover]

winecat, I've been taking it to local mechanics who read it for me for free. They showed me the code reader and the codes that came up so I know it was legit.

[sapphireblue]

I had that problem in an older Toyota I had. We had it fixed for various things but inevitably the light would come back on.

So I decided to ignore it. I got the car serviced as needed for inspections, tune-ups, oil changes, etc. and they would adjust it so the light would be gone but it would come back quickly.

After a couple of years of ignoring the light, it went away! I told my husband excitedly and he was like "the fuse for the light bulb probably burned out after being on continuously for years" but I choose to believe it fixed itself.

[beerlover]

sapphireblue, I will probably get it checked out one more time, but that might be my next plan lol, just ignore it. So over it.

[wildrice]

My light came on regularly on my 2010 Jeep. No shop ever found an urgent issue to fix, so we left it. This probably happened on and off for 3 years. We lost the Jeep last fall so who knows what would have happened long term, but I would vote not to bother with it if they cant identify anything major to fix. I think sensors can be oversensitive.

[hamster]

Try replacing the gas cap, that solved my recurring issue.

[Patsy Baloney]

Check engine light oddities tend to be an in-advance sign of battery issues in my car (08 Ford Fusion). It will come off and on for a few months, and then my car's clock will reset, a few weeks later, it will get hard to turn on, etc.

[mich1]

Yes. On my 2007 Forester.

By any chance, are you using cruise control when it goes on? About 75% of the time we use cruise, my check engine light goes on, and this is the ONLY time it goes on. The car has no other issues, other than the damn light. Mechanics find nothing. We have taken to resetting it ourselves.

Your car is about the same age, maybe the same thing?

[dirtyred]

Feb 13, 2020 9:10:43 GMT -5 carmenere said:

Have you checked that your gas cap is on tight? That was a constant issue with my last car.

With my DH's as well.  He bought a locking gas cap and that fixed it.

[beerlover]

Maybe I will try the gas cap thing. Mine is one that you're supposed to just turn until it clicks once. And I follow those instructions lol. It didn't occur to me that it might not be on tight. Wouldn't you think a mechanic would've checked that?

mich1, I'm sure this is weird but I've literally never used cruise control in my life.

[tripleshot]

Just put a piece of black electrical tape over the light. Problem solved!

[fumbalina]

There check engine light is not a scam but it is often on for emissions problems and they can be difficult to repair. On many models there are multiple O2 sensors as well so even if you already replaced it, there can still be a had one.

I always buy used cars but I will not buy with a check engine light. If the battery is disconnected it takes about 50 miles to be readable. I found many cash car places leave dead batteries so it does not show.

[beerlover]

fumbalina, this car was my grandmothers and I've had it since 2012 when she died. I've never had any issues with it beyond routine maintenance until now :/

[sakura]

Diagnosing a check engine light can be a bit of a process of elimination and it’s common to start with the cheapest/easiest to replace stuff first so I don’t think you’re getting scammed, if that helps any. I’d just koko if things seem to be running fine, but if the check engine light starts flashing, that’s a sign that there’s a serious problem and you could be damaging your car if you keep driving. Driving slow to the mechanic at that point is probably fine, but no highway driving.

[Nonny]

As the others have said the check engine light isn't a scam, but it's kind of a catch all. 

The common culprits are things you've already replaced like sensors (O2, mass air flow), spark plugs, and the gas cap like PP have said.  Generally speaking if it's on solid, it's less dire than if it's flashing at you, but it's still not good. If it's flashing make a note of the pattern, because it's a kind of ridiculous diagnostic Morse code that can sometimes be helpful in diagnosing the issue.

Also make note of when it comes on. Is it always 1/4 of a tank into filling up at a certain gas station? (If, so stop getting gas there.) Only when you've been driving at freeway speeds? Only in stop-n-go traffic?

I personally can't really diagnosis these things, but my H has the cable and software for our cars, and he always wants to know these bits of info when he's plugging it in to pull the codes, and so if he needs to drive around with a laptop hooked up so he can repro the problem.

[alleinesein]

2001 BMW. Check engine light was on for 1.5 years and every diagnostic test said there was nothing wrong (no codes). Only thing that it did that wasn't normal was a rough idle when I would start the car. We finally figured out that there was a leak and the air intake was getting jacked up and triggering a sensor that caused the light to come on. It was around $600 to fix the issue and now it runs fine (and passed smog).

[Aquatica]

Hi, my husband has been a car mechanic since 2003, a Toyota T-TEN graduate, and now does it on the side since he works on aircraft. This is his take:

"Did the mechanic sit down and go over a repair plan according to tech service bulletins for that specific check engine code for your year make and model of vehicle? Commonly, there is a hereditary fault that corresponds with a specific check engine code for your year make and model of vehicle. Also, confirm that the technician working on your car has the latest diagnostic technology on his scanner called a scope that allows for in depth diagnostics of engine controls which are primarily the reason you'll have codes. But more importantly, is the repair plan that you and the service writer develop. Understanding the diagnostic troubleshooting path assists with time, money, and efficiency. What you're really doing is developing a peace of mind. If they're replacing parts and not correcting the original problem then they should reimburse you all labor for repairs besides the hour that is common for the diagnostic process for the problem."

[beerlover]

Feb 13, 2020 19:52:36 GMT -5 Aquatica said:

Hi, my husband has been a car mechanic since 2003, a Toyota T-TEN graduate, and now does it on the side since he works on aircraft. This is his take:

"Did the mechanic sit down and go over a repair plan according to tech service bulletins for that specific check engine code for your year make and model of vehicle? Commonly, there is a hereditary fault that corresponds with a specific check engine code for your year make and model of vehicle. Also, confirm that the technician working on your car has the latest diagnostic technology on his scanner called a scope that allows for in depth diagnostics of engine controls which are primarily the reason you'll have codes. But more importantly, is the repair plan that you and the service writer develop. Understanding the diagnostic troubleshooting path assists with time, money, and efficiency. What you're really doing is developing a peace of mind. If they're replacing parts and not correcting the original problem then they should reimburse you all labor for repairs besides the hour that is common for the diagnostic process for the problem."

Thanks for your husband's input!! Not exactly. No one mentioned anything about tech service bulletins to me, nor would I have had any idea I needed to ask about that (ugh, this stuff is so annoying. Why do I need to be an expert in this too?!) lol.

I first took it to a local guy with his own shop, who looked everything over very thoroughly, checked for leaks and everything, and diagnosed that the only problem he could see was with the O2 sensor not responding, so we replaced that first. He did acknowledge that this was his hypothesis and it could be something else, but all evidence was pointing to that at the time. So we replaced it, and the spark plugs because they needed replaced as well. My car was good for probably 1.5 months. Then, the check engine light came on again. Took it back to the same guy, who said that this time, it seemed to be the mass airflow sensor. He was going out of town for awhile and not able to do any work until the end of Feb., so I took it for a 2nd opinion to another, larger local shop to see if they said the same thing. They also told me it was the mass airflow sensor, so I had it replaced last month. And again, the light is on. So clearly it's not that either.

My friend came over with a code reader and the code it's showing is P0171-system too lean bank 1.  Would you mind asking your husband if it would be better to go to a Toyota dealer for this type of thing?

[sagelily]

This was happening in my 2011 Subaru Outback. We replaced multiple smaller things and it kept happening with increasing frequency. It got to the point the dealer had my car 3, 4 days at a time to evaluate and I would have it back less then a week before the light was back on again. In my state the car will not pass the annual inspection with that light on so I was becoming increasingly desperate to find a solution. H did research, felt satisfied it was nothing that would be an immediate serious issue and bought something on amazon to reset the code ourselves. It has now been a year and a half without the light ever coming back on. It did cause the battery to reset so I couldn’t get it inspected without driving at least 50-100 miles. My car passed emissions with no issue.

I think you mentioned you were not being charged for each reading but our costs were adding up with no end in sight and I was not willing to get a new car. I like driving my Subaru but worked with 2 dealers (one closer to home and one to work) and was really unhappy with each. It was a waste of time and money.

I don’t know exactly what he bought to fix it but I think it cost about $15-20. I can look in our amazon history and update tomorrow.

[beerlover]

sagelily, wow that's so frustrating! I live in PA and my county doesn't even require an emissions inspection so that's thankfully not an issue for me. I would have been desperate for a solution too! I'm also not really wanting a new car, this one is already paid off! I'm glad your solution worked for you and definitely interested to hear what you bought, for my own future reference.

[Aquatica]

beerlover

My H's response:

"You have money invested into the shop where the mass airflow sensor was replaced, in the form of labor price. If you take your vehicle to another shop, you lose that amount. If that amount isn't something you mind parting with, yes take it to the dealer. You pay more in labor, but they have more ability to make an ongoing problem more affordable to you. If not, you have a good case to roll the labor you paid into the next repair to fix the issue, as the first part fixed nothing."

[agnes]

My H response:

p0171 is a lean condition on the intake system AFTER the mass air flow sensor. i would be looking at vacuum hoses, the air intake tract, breather system etc, possibly intake manifold gasket/seals etc.

the P codes in a car are a universal standard since the advent of OBD2 in 1996, the powers that be decided there needed to be a standard method of diagnostics.

often times a p0171 code will in fact be a faulty mass air flow sensor, but in reality, its a lean condition that the air mass sensor is picking up, basically saying that the air mass sensor is reading X but the other sensors are coming up with a different value, so it triggers the light for the air mass sensor, since that is the system that reads air intake volume.