P1131 HO2S Bank 1 Sensor 1 Signal Below 0.45v

[Duff750]

Did a little searching and lurking to see if I could find anything before I went botherin' y'all...but didn't see much that matched the problem I'm having, so figured I'd go ahead and post up.
I've got an 02 Protege I bought about 6 months ago. It ran great for about the first 3 months then this problem started.
I was sitting at a stop light one day, sat there for about 15 seconds, then the car kinda studdered as if the A/C Compressor was kicking on..but it wasn't. Didn't think anything of it really until I saw the CEL come on. By the time I got to an Auto Zone to pull the code, the CEL had already cleared and there were no other problems. After about a week it did it again but a little more violent this time... then the occurances got closer and closer together, to the point where I now have to put the car in neutral if I come to a stop for more than 2 or 3 seconds and keep my foot enough on the gas to keep the revs up around 1500, else the car just flat out DIES. If I don't do this, and it gets its chance to studder, then when I do finally get to go from the stop, I have to bury my foot to the floor to get the car to even begin to move...then it all kicks in at once after about 7 seconds. but spits and sputters up to about 20mph then it's fine till the next occurance. I finally got a chance to pull the code from the CEL and I got P1131 HO2S Bank 1 Sensor 1 Signal Below 0.45v (A/F Ratio Too Lean)
The guy at Auto Zone recommended I toss some injector cleaner in the tank, so I did... But it didn't help even the slightest. Has anyone else had this problem? If not, can someone point me in the right direction of what I may need to check out to get the car back to an accepable working condition? Thanks in advance for any and all help!

-Duff-

 

[slavrenz]

Duff750,

I have posted the pages from my repair manual that cover the diagnosis of the code P0131, which is what I assume you're referring too (P1131 is not a valid trouble code). The issue is stuck low voltage on the front O2 sensor, but unfortunately, it could be anything from a clogged fuel injector to poor compression. Follow these steps and it should solve your problem.

 

[funktownp5]

Just replace the primary O2 sensor, its probably bad and not giving any

voltage to the ecu.

 

[Duff750]

Can't remember what the actual code number was that they pulled at Auto Zone, but the trouble description from this website http://www.obd-codes.com/trouble_codes/mazda/ is the correct description...just pulled the 'P-Code' that was on that website and pasted it here

 

[slavrenz]

Those are just the Mazda specific codes, meaning that they were developed by Mazda for the ECUs in their cars only. However, the list covers more than the Protege, and there is no "P1131" code for the Protege. This list is also missing all of the codes that must be programmed into every car's ECU - the ones that start with "P0XXX".

The P0131 code refers to low O2 sensor voltage, and I'm pretty sure this is the one you're talking about. If it just started happening, though, I would either suspect a bad O2 sensor, a bad ignition coil, a bad PCV valve, or some sort of fuel system blockage.

 

[Duff750]

When the problem first started it was very minor, and then gradually got more violent as time passed...though I'm no mechanic by any means, I'm going to say it's probably not the O2 sensor if it gradually got worse rather than just staying minor. Guess I'll check the ignition coil, PCV valve and fuel system....and might as well check the sensor just for good measure. I'll post results for future newcommers with similiar problems.
Thanks for the help fellas

 

[Duff750]

Turned out to be a crack in the bottom of the Mass Air Flow Boot, was tripping out the Mass Air Flow Sensor. Little bit of duct tape did it well until the new boot comes in