Code Help
 

Hi I just pulled some codes off our 2001 MPV and was wondering what they mean?

We've had the van for almost 3 years and the CEL came on once when we drove through some water. I thought nothing of it and the CEL is no longer lit.

However these codes came up when I plugged in an Actron scanner:

P0031 - HO2S Bank 1 Sen 1 Heater Circuit Low
P0171 - System too lean Bank 1
P0174 - System too lean Bank 2
P0300 - Random/multiple cylinder misfire
P0481 - Cooling fan 2 control circuit

Can somebody enlighten me on what these codes mean and how to fix them?

I'm guessing a tune-up will remedy P0171, P0174 & P0300?

Thank you,

Shawn

RE: Code Help
 

Oh I left a couple things out.

1) When running, there is a very strong gas odor that comes from the engine/front end.

2) There is a hissing sound coming from the back of engine compartment on the drivers side. This existed long before the odor.
I sprayed the small belt located on the side of motor (drivers side) and that did nothing. Initially I didn't think the sound was coming from there, but I tried anyway and still the same.

Any ideas for either problem.

Thanks!

RE: Code Help
 

Wow. When you get a CEL on you do not fool around there spierce:D

Should not take too much to get them all figured out. We'll start with the two easy ones. Good description of all symptoms always very helpful.

P0031 is telling you that theHO2S12 heater has low input. In english that means that the O2 sensor located in the right bank (closest to the windshield side and radiator side ) of the exhaust manifold has burned out and is open circuit. A new oxygen sensor will correct that code. OE part number
GY03-18-861B-9U available from www.onlinemazdaparts.com for $101.80. $26 less than dealer price.

P0481 should not exist for this year vehicle and is just a PCM glitch due to incorrect programming. You would need to get the PCM reprogrammed to latest calibration to get this one. See link below to TSB.
http://www.mstore2000.com/PDF_Files/01-006-03a.pdf

The other 3 codes P0300, P171, and P174 are probably all due to the same problem. Engine is running very lean and even missfiring due to being so lean. You also reported hearing a hissing noise from the back of the engine. Would suspect that noise is your vacuum leak. Carefully check that area for disconnected or damaged hoses. Pinching off vaccum lineclose tothe manifold sometimes works also. If you pinch off a certain line and the noise stops you know what area to look at. Spraying lightly with some brake cleaner can often find a leak also as the rpm will ususall raise up when you hit the vaccum leak area. It is very flamable so be very careful as a errant spark from bad wires can cause this to ignite. Pay special attention to the intake manifold gaskets as these have been a long time problem on the 2000-2001 and updated gaskets are available.
Fuel odor is just going to be a matter of visually inspecting the lines to see any drips or damp areas.

RE: Code Help
 

Hi babyhuey,

Thank you for responding. I had a feeling P0031 was a sensor malfunction. Is this sensor bolted into the exhaust & easily accessible?

I read the PDF regarding the P0481 code and it sounds like something that requires special equipment to do. Can this glich be ignored or should I seek a mechanic for this?

In reference to the other 3 codes, what does "lean" mean in automotive terms?

The engine feels like it stutters (slight bogging) when it's at idle. I figured it could be the plugs or a vacuum leak as you said. I will inspect the vacuum lines & try your pinching technique. I would also like to do a tune up but it looks like the manifold needs to be removed and there's many parts connected to it. I am pretty mechanically inclined and have some advanced work on cars, but this job looks a little intimidating. Is this easier than it looks, or would you recommend seeking a pro for this?

Also, I would like to purchase a good, thorough manual for this van - any recommendations?

Thanks again for your help!

Shawn

RE: Code Help
 

The oxygen sensor in question is the only sensor or anything for thatmatter that is installed into the right side exhaust manifold. A 22mm open end wrench or specialty socket willbe needed to remove and install. Is not very accessable as the intake manifold blockseasy access.
The P0481 isa reprogramming procedure that can probably only be carried outby dealer or a Mazda speciallty shop that hasthe right equipment. It can be easily overlooked if you do not mind the CEL coming on. It may well never happen again.
Leanrefers to theratio of airto fuel in the combustion process or mixture. Too much air or not enough fuel iscalled Lean. Too much fuel is called Rich. Since you have reached the lean limit of your computer systems ability to adapt to mixture changes it has turned on you CEL and set codes to let you know this. If you keep track you are probably getting much worse fuel economy as the engine computer has been adding fuel on a continuous basis to try and compensate for this lean conditon.
The intake manifold looks intimidating but really is not that difficult to remove. It is even lightwieght plastic which is nice. Would try to pinpoint if and where you have a vaccum leak first and then have an O2 sensor on hand before attempting to remove manifold. O2 replace will be much easier with maniold off.

RE: Code Help
 

I had just removed an O2 sensor off the cat on my VW last weekend. That was a pain but it finally gave way. I've read it's easier to do while the exhaust is warm. However, if I do this after pulling the intake I should be OK (he knocks on wood).

The CEL light is not even on. I needed a scanner because I just fixed my dead VW this past weekend and needed to pull codes. I figured I'd connect it to the MPV out of curiosity to see if anything would come up. And to my surprise - the codes I stated earlier. I still have the scanner so I will clear the codes in the meantime and see what happens in the future.

Based on what you described with the "lean" terminology, and the stuttering & strong fuel odor I smell, I am guessing there is a leak in my fuel line. Believe it or not, I still haven't had a chance to inspect the van (wife & kids).

The manifold looks like it's easy to pull, just alot of things connected to it. That's why I would feel better having a good manual before pulling stuff off. Can you suggest a good manual for this vehicle?

Thanks again for your help!

Shawn

RE: Code Help
 

The only manuals that I like to use are the Factory service manuals. Repair manuals are usually $150 and wiring diagram manual is $75 or so. Well worth the investment if you plan on keeping the van and doing most of your own repairs. You can get them a little discounted at www.onlinemazdaparts.com.
I also see a variety of different ones available on ebay motors from time to time.

RE: Code Help
 

baby huey! are you still out there? i am having the same problem/problems with my 2002 MPV. How many O2 sensors are there for this van? 4? Also, will replacing the sensors stop the van from sputtering at idle, or do they simply tell about the lean trouble?
thanks for your help
brian