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The ECL was on on rmonth ago. The Smog check failed becasue of this. the error code was p1133. I continue driving it and the light went off after 200 miles. I knwo the computer in the car has a buffer to rememebr everyhting, so I kept driving for another 2 weeks to make sure the old record got overwritten.
500 miles past in last 2 week, today I went to re-do the smog check. the p1133 code is gone. But OBD II failed agian becasue of a new code - p0171 (system to lean). So frustrated!
What does this mean? Does this mean I still have to change the O2 sensor? (It's damn expensive -- $350 parts + $60 labor). Or, does this mean If I drive more it can be recovered? Or Is there any way to reset the computer?
The DMV renew is due in a week. I feel so bad now... Your help/suggestions will be hightly appreciated!
i never heard of an o2 sensor costing so much!!! 60 for parts and you can buy a wrench for $3 and get it done your self in a hour with a wrench and a knife if you go after market o2 sensor. you can reset the ecu by pulling the fuse when your a block away from the check point and then drive slowly there and have them check it. oh and yes you should replace your o2 sensor search the site to find out which one it is ... there is 2 one before the cat and after
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^ and leaving it that way!
Sadly, it's true. The grarge guy told me the sensor cost $350 plus labor. I called Toyota dealer, they told me $370 + labor. They told me the sensor is for california and has the special wire/connector. I think it won't be wrong since I checked with two different sources. :-(
"you can reset the ecu by pulling the fuse when your a block away from the check point and then drive slowly there and have them check it."
hmm, where is the fuse? Doesn't computer remember the history status even when the power is out? Do I need to drive a while to have the computer forget the 'old memory'?
I replaced my MAF sensor to fix this problem.
Symptoms: Knocks going up hills and accelerating. Premium gas used to make it better, but it got worse. Fix: After replacing my MAF sensor ($135, and a screwdriver and 5 minutes work!). IT RUNS GREAT!!! Toyota manual lists 5 different fixes for this problem... Don't think that it is always the ($300) O2 sensor!
Here is finale of my story. I decided to WAIT for another week. Then, I went to the smog check place again. Guess what? All error codes are gone. That's the last day of the smog check due day. I win this bet. :-)
Let me replay the whole story at here:
1. engine check light is on.
2. smog check failed becasue p1133. (only p1133).
3. the O2 sensor + labor cost more than $350 so I decide to wait. why? I read the TOYOTA manul, it says light on and off can be caused by many factors. Sometimes it will go off after drive a while. After the engine diagnosic, I was told there is nothing wrong but p1133. So, I decide to drive few hundrad miles to see what happens.
4. After 200 miles, the engine light went off, but p1133 code is still there. I believe there is a buffer in on-board computer. So it will take a while to clear the old record. Friend told me it might store 45 records in the buffer.
5. After 1 week, went to smog check place again. p1133 is gone. but p0171 is on. Damn it! They told me it's 'system too lean'. Could caused by the low voltage in bank1 because of the 'bad' o2 sensor. hmm, that expensive sensor again?!
6. I'm not convinced. It could be the computer buffer factor. Or other minor causes. There are many factors can cause 'system too lean'. So, I decide to wait longer.
7. After another 300 miles, and it approaches the last day of smog check report. I drove to the smog check place again. This is a big bet: 1) pass, or 2) spend $300+ to fix the sensor immediately...
8. And I won! All error codes are gone. The garage guy said he couldn't believe that I did nothing to fix this problem. haha, he is learning too.
I'll keep an eye on this issue if it happens next time. But it's not that uegent now.
I do have a confusion though. WHY every mechanic say I have to change the o2 sensor? I think the sensor is used to detect error condition. If the light is on becasue sensor found a spike condition, why do people always want to change sensor? It actually means the sensor is doing its job. When the error code is in computer, it'll take a while to be cleared if the error doesn't happen again. I don't think there is anything wrong with the sensor itself. If there is really problem, we shall fix the root cause (what caused the air/fuel error condition) instead of just change the sesor and reset system. It actually proved my guess in this case.
I know nothing about the car machanics. I just follow my engineering thoughts to draw this conclusion. your reply and advice will be helpful.
I hate to bump an old thread, but I'm having the same problem. My engine is a 1mz though. It comes up with that same P0171 code (system too lean left bank), twice. Yeah, that's right, it comes up with the same code twice. I just replaced the O2 sensor, and that didn't help, I feel like I wasted $110 even though I know it probably needed it anyway. So how much do those MAF sensors cost? Will I have to buy one from Toyota if it is bad?
Try cleaning the Maf sensor, clear the code and see how that works, usually that solves the problem . Use a spray cleaner designed to clean electrical parts.
Thanks, I'll do that. Where can I get that electronic cleaner stuff, though? Also, from what I remember, the 1mz's MAF sensor isn't like the one in that article...that is, the wire's can't be seen from the outside like that. It's sort of a conical shape with a hole in the end, and the wires are inside of that. But maybe there is some access point that I don't remember. Should I just spray the cleaner inside the hole or what? What it's saying makes a lot of sense though, since I have an SRI installed and I haven't cleaned the filter at all since I put it on back in May.
Ok, I went to AutoZone and bought some electrical cleaner, then did my best to clean out the MAF sensor. From what I could see, it didn't even look dirty, but I thought it was worth a try. Well, guess what? It didn't do a thing. I had them reset the light, and two miles later, it came back on. I didn't notice a difference in performance while the light was off. I really hope that the MAF sensor is not bad...they're bound to be expensive. Also, I believe I have some sort of vacuum leak, could that be what's causing it? See, it idles rough, and after you clear the code, it makes a sort of sucking/squirting noise, and the motor shakes when it does it. Could it just be a malfunctioning ECU? Ugh...any way I look at it, it's beginning to seem like I should just have it looked at by a professional. There are too many things that could be causing this light to come on. Please help!
Yes an air leak can cause the po171 problem. Possible causes...air intake hose leak(loose), fuel line pressure, fuel injector blockage, heated o2 sensor malfunction, MAF, engine coolant sensor.
You may have to remove the MAF to clean the wires with the cleaner and a q-tip gently.
Some examples:
__________________ It worked fine until I fixed it!
Yeah I removed the MAF and cleaned everything, that didn't help. Like I said, I could barely see the sensor inside, if I took a picture you wouldn't be able to see it, it's not exposed like that one is. However from what I could see, it didn't look dirty anyway. I had my car scanned by a shop with one of those snap on scanners, the big kind. They showed me what exactly my car was doing as far as the MAF and O2 sensors go. The MAF is fine, but the O2 sensor on the left bank (closest to firewall) says it's running lean. They then said that it's caused by a vacuum leak, and that I ought to have them hook it up to this smoke machine that pinpoints leaks. They wanted $30 for it though so I didn't do it....thinking that I could just pinpoint the leak myself with a stethoscope. Well, I couldn't, so I'm probably going to take it back tomorrow and have them do it. Although, it could still be the O2 sensor malfunctioning, since the one I replaced was the one in the front. But knowing my luck it's probably a combination of both.
If their test showed the sensor to be running lean then that's probably the culprit. You can check all of your hoses by removing and cleaning them.
You could have some partially clogged hoses or hairline cracked hoses leaking. I'd go with the o2 sensor since that's what their scanner detected. Good luck.
__________________ It worked fine until I fixed it!
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It worked fine until I fixed it! 
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