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Engine light is on. mechanic say system is running too lean. What is that means?


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I bring the Warrior to Mechanic for the oil changes for the RV season. Next thing I know Engine light is on while I on the highway

Last used at  February  without any issue and filled with non ethanol gas until now. 

Any suggestions?

Thanks in advance.

20180513_103654.jpg

Edited by chang50012
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Ethanol has nothing to do with it.  If it has an O2 sensor issue it will throw a code but that does not mean it's lean just that the O2 reading is out of range. If the O2 voltage is low it's lean if the O2 reading is high it's rich. Now your MH has 4 O2 sensors (2 maybe Lambda  sensors I don't remember)  any of them will register a code replacing them all will be expensive and won't necessarily fix your problem. They can be checked individually they do go bad they only last so long. The O2 sensor is a very common code but there are other sensors that can lie or really tell you the truth, the normal response is "it's lean". What I'm getting at being a "92" there are a lot more sensors and complexity to the FI system than an old 22RE you need to find some one that has been there before not some who replaces parts till the code goes away.

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Run a bottle of Techron fuel injector cleaner through the system. Follow instructions EXACTLY paying special attention to one bottle to 15 gallons or less & insert at empty before filling. Bet you'll be pleasantly surprised. 

  

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Same code on my v6. I changed out the o2 sensor (easy, used a denso like oem, underneath at driver seat level) but I thought there was only one 02 sensor on these???

Light still on. Will try the techron or gumout injector cleaner.

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If you own a volt meter and know how to use it they are fairly easy to check. What does the diagnostic code come up with? There are 4, 2 up stream and 2 behind the cat. The 2 behind the cat are O2 sensors the ones before the cat maybe be lambda sensors if they are they will be different. One thing for sure the injector cleaner won't hurt any thing but is unlikely to fix any thing either. I might add they are heated sensors this can play into the mix because they have been known to internally leak voltage to the O2 output voltage slewing the figures.

Edited by Maineah
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A small jumper wire (under the hood) is used to get the CEL to flash - there is a pattern that translates into a number.  These computers are pre OBDII and hence the info given is a bit cryptic.  It is fairly easy to the jumper thing.  Hav e you downloaded a copy of toyota service manual yet?   

 

based on the number you have,  you get  a list of things to try.  The problem is that sometimes the codes are misleading. 

I had a CELof 20 when my RV was about the same mileage and had not been driven a lot.   After much troubleshooting the dealer (3rd mechanic to look at it) threw an O2 sensor at it and that fixed it.

The mass air flow and 02 sensors are life limited - if you get a 20 I would throw the MAF at it first then the O2 sensor.  If you have a friend nearby, the MAF is easy to change and you could swap to see if the problem changes vehicles.

TO clear your CEL, you can pull the ECU fuse in the fuse box under the hood or disconnect start battery.  Both will reset the CEL.

 

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the "running lean" comment might be referring to the closed loop system that the vz3e engine uses.   Essentually, once the engine reaches operating temperature, the ECU (computer) looks at the air coming into the engine via the MAF, the throttle position, the O2 data (measures mixture detected at the catylic converter - there is ONE O2 on these engines).  The computer is varying the amount of fuel being squirted into the cylinders - also varying ignition timing/ advancing up till the knock sensor starts to report knocking-then backs off a bit)

This is a simple explanation, but bad sensors and/or vacuum leaks can cause problems.

 

 

Attached is some pages from a service manual showing HOW to read the codes......   note the jumper needs to rather small - if you push hard you can push the receptacle out of the harness,

 

p460-466.pdf

Edited by DanAatTheCape
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