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Check Engine Light

by Styan, February 20, 2007

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My 2000 corolla's check engine light has been coming on over the past 2 weeks.

I brought it in to the garage, and my mechanic pulled a P0172 (system too rich) from the OBD. The first time was 2 weeks ago, he cleared the code and told me it was likely just from the cold (it's been hovering around and below -15°C (5°F) over the past 2 weeks overnight here).

Then last weekend it came on again, I brought it to him and he cleared it again telling me it was likely due to the cold, and wasn't worth spending the money to try and fix it until it warms up outside. He figured if it came on again, I should ignore it until it does warm up.

I just got into work today (this being the day after he cleared it for the second time), and the light came on again. I don't have an OBD-II code reader so I don't know if that's what it is this time around, but its counter intuitive to be ignoring a light that is telling me something is wrong.

Can anyone recommend a course of action. I'm thinking about going to another mechanic to see what they say, but I really like the guy I have now, hes good about the little things and hes been servicing my dad's car for over 12 years.

More detail on the code: http://www.obd-codes.com/trouble_codes/gen...ygen-sensor.php

EDIT:

A few extra details,

I changed the air filter before the winter, mileage: 156,000 kms, I bought the car used last april, at 142k, had the oil changed when I got it, and then changed every 5000 km thereafter, It does eat oil and I've been trying to keep an eye on that, but its run low on a few occasions.

thats not normal and dont ignore it, you could be looking at a new O2 sensor and cat sooner than you need them. it could be, as that link suggested, a dirty MAS, vac leak, or its possible that theres a small fault in the ignition system (bad/loose wire, improperly gapped plug) thats causing an incomplete combustion not severe enough to set a misfire code but enough to trip a too rich code. or if you topoff your gas tank you could have flooded the charcoal canister with fuel, and when the system purges it could be dumping alot more fuel into the mix.

Since it is the first year that they introduced the MAF sensor to the 8th gen Corolla - I would try cleaning that up first. Usually not a normal maintenance item, but has gotten much attention in the past few years as a common trouble spot for certain spurious CEL codes. There are a few links here on how to clean the MAF sensor. Like Bitter mentioned - check the plugs/ignition system - Iridium plugs have a very long lifespan, introduced with this model year, but couldn't hurt to pull the plugs and see how they look. Also when they introduced different injectors - the 12-hole variety for better fuel atomization, also tends to clog on occasion. Might want to hit that with some fuel injector cleaner and see how the engine responds. Throttlebody should also be cleaned, could be a sticking throttle plate or heavy varnish deposits in there.

Can the car be driven with this problem without causing damage? As I understand it the major disadvantage to running with this condition is excessive fuel use.

If I can get my hands on an OBD-II reader, I'd be able to check and clear the code if its the same code, and not worry about having a check engine light that could be showing something worse. I'm still not sure what course of action I should take with it, if my mechanic says to wait until it warms up.

Cars really aren't my area of expertise, what I was in need of was a second opinion and your input has helped... as much as I enjoy taking things apart and putting em back together again, I don't think the car is something I want to start doing that to.

Thanks for you replies.

Cars really aren't my area of expertise, what I was in need of was a second opinion and your input has helped... as much as I enjoy taking things apart and putting em back together again, I don't think the car is something I want to start doing that to.

c'mon... you know you want to do it. everyone's doing it these days! Just one time won't hurt! It's not an addiction, I can quit whenever I want!

Just trying a little humor. Seriously though, cars aren't that different from anything else you might take apart and reassemble. And they can be loads of fun to work on. On the other hand, they can be as frustrating as anything else too.

Once you get past that initial "what am I doing!?!" stage, it gets much easier. And you'd be surprised just how much you learn and how much of that transfers to almost all other vehicles.

Good luck with your problem. I'm afraid I don't have any advice for you except to say that everything listed so far is something that is easy to do and is difficult to mess your car up by doing.

jim

Can the car be driven with this problem without causing damage? As I understand it the major disadvantage to running with this condition is excessive fuel use.
Can you keep driving with this problem? Sure, but I wouldn't. As mentioned before by Bitter - you can harm other components by continuing to drive in this manner. Either from excessive amounts of deposits to running components out and beyond tolerance ranges. The 1ZZFE is pretty well tuned from the factory, running it outside of spec can cause problems down the road.

 

 

I called my mechanic again, he said he'd be able to look at it on Thursday.

Bikeman982

I called my mechanic again, he said he'd be able to look at it on Thursday.
CEL should not stay on. It means something is wrong with the engine and it requires replacement/repair.

 

Let us know what he finds.

So, he ended up giving the car a fuel treatment, and new plugs, he said one of them was really gummed up. At the same time he gave it a minor tune up, making sure miscellaneous things were in place and clean. Since I picked it up yesterday, I've driven it about 65 km and no light. It was -12°C here last night. I'll be keeping an eye out for it.

Thanks again for everyone's input.

The light came on again this evening on my way home from work... default_sad

I think it's time to find a new mechanic. He's trying to replace simple things hoping they fix your problem. Did he he ever check the output voltage on the O2 sensors to see if they are within spec?

Trial by error fixes cost more money in the long run.

We'll I think I have a bigger problem on my hands...

Tonight, the car started fine, reversed fine, but when I put it in drive and it shook to a stall. Started fine again, and when I stopped at the stop sign the lights all dimmed and it sounded like it wanted to stall again, nearly did but I hit the gas.

Doesn't seem to be able to sustain enough power to run when idling in gear. Alternator maybe? Anyway I'm tired and kinda upset so I'm going to bed.

Bikeman982

We'll I think I have a bigger problem on my hands...

Tonight, the car started fine, reversed fine, but when I put it in drive and it shook to a stall. Started fine again, and when I stopped at the stop sign the lights all dimmed and it sounded like it wanted to stall again, nearly did but I hit the gas.

Doesn't seem to be able to sustain enough power to run when idling in gear. Alternator maybe? Anyway I'm tired and kinda upset so I'm going to bed.

Sounds like it is losing power - such as a drained battery or getting a bad alternator/regulator.

 

 

Yup, my car absolutely hates me... Brought it in today, there were no codes (even in the history) and it wouldn't act up for him he took it out and drove it on some side streets, and a spin on the highway, let it idle for some time too with no ill effects. If anything changes I'll post.

Bikeman982

Yup, my car absolutely hates me... Brought it in today, there were no codes (even in the history) and it wouldn't act up for him he took it out and drove it on some side streets, and a spin on the highway, let it idle for some time too with no ill effects. If anything changes I'll post.
The car knows when it is the dealer checking it out and they don't act up then.

 

Wait until you get it alone again.

Light came on again last night, I brought it in this morning, P0172 "System too rich" is still one of the codes, now hes also pulling a P0300 "Random/Multiple Cylinder Misfire Detected".

We looked at the live data on his scanner and there were no misfires on any of the 4 cylinders at the time we had it hooked up.

Any ideas?

With the engine running at night, spray the ignition area with a hand sprayer/mister and see if you get a light show and/or the engine stumbles. If you do, this area needs some attention.

I wonder what brand plugs he installed.

Light came on again last night, I brought it in this morning, P0172 "System too rich" is still one of the codes, now hes also pulling a P0300 "Random/Multiple Cylinder Misfire Detected".

We looked at the live data on his scanner and there were no misfires on any of the 4 cylinders at the time we had it hooked up.

Any ideas?

The lights most likely dimmed because the RPMs dropped due to the poor engine performance. I don't think you have to be concerned about a battery or alternator problem......

We'll I think I have a bigger problem on my hands...

Tonight, the car started fine, reversed fine, but when I put it in drive and it shook to a stall. Started fine again, and when I stopped at the stop sign the lights all dimmed and it sounded like it wanted to stall again, nearly did but I hit the gas.

Doesn't seem to be able to sustain enough power to run when idling in gear. Alternator maybe? Anyway I'm tired and kinda upset so I'm going to bed.

The lights most likely dimmed because the RPMs dropped due to the poor engine performance. I don't think you have to be concerned about a battery or alternator problem......

We'll I think I have a bigger problem on my hands...

Tonight, the car started fine, reversed fine, but when I put it in drive and it shook to a stall. Started fine again, and when I stopped at the stop sign the lights all dimmed and it sounded like it wanted to stall again, nearly did but I hit the gas.

Doesn't seem to be able to sustain enough power to run when idling in gear. Alternator maybe? Anyway I'm tired and kinda upset so I'm going to bed.

I agree with you here, it was the rpms dropping and not an alternator related issue.

What exactly do you mean by light show?

You might see some arcing under the hood. You might also hear it crackling as well if there are major shorts.

I agree with you here, it was the rpms dropping and not an alternator related issue.

What exactly do you mean by light show?

Bikeman982

You can always meter the wires.

Faulty plugs, replaced again -- no charge... now we play the driving and waiting game to see what happens.

Bikeman982

Faulty plugs, replaced again -- no charge... now we play the driving and waiting game to see what happens.
Were all the plugs bad, or just one??

 

I bet all were changed, even if only one was bad.

Well, as I went to pick up the car, he told me he didn't use the iridium ones that were recommended the first time... so they were faulty because they weren't the right plugs. (last week he did all 4, now all 4 have been replaced with the proper plugs).

Bikeman982

Well, as I went to pick up the car, he told me he didn't use the iridium ones that were recommended the first time... so they were faulty because they weren't the right plugs. (last week he did all 4, now all 4 have been replaced with the proper plugs).
By "proper" you mean the stock plugs?

 

 



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