I have a 1999 Mazda Protege 1.6L manual. I am experiencing sluggish performance and poor fuel econonmy. My check engine light is on and indicates a touble code of P1141. I do not have access to a list of Maxda codes, but have looked at generic OBD II codes. From what I can ascertain this may indicate a bad 02 sensor, which would I guess cause the PCM to go into an open loop mode and thus give me the symptoms I am experiencing. What I came up with was H02S Bank 1 sensor 2 Heater Circuit Low Input, but this may not actually be the right code for a Mazda. Does anyone know what this code indicates? Any suggestions would be appreciated.

 

You are right. P1141 indicates a fault in the rear O2 sensor heater circuit. The heater is used to help sensors warm up faster so engine can enter closed loop quicker and lower emissions. The rear O2 does not play any role in controling fuel mixture however. It is used only as a way for the engine computer to monitor the front warm up cat converter efficiency. The front O2 is the one that tells the PCM what currect mixture in exhaust is so it can adjust the fuel accordingly. Very unlikely that the code is the source of poor fuel economy and low power. Look instead to the mass air flow sensor on top of the airbox. Has a very high failure rate with problems that you are describing. Have had some luck cleaning these sensors but yours is covered under an extended warranty for 7years or 70,000 miles I think. The extended warranty is available thru Special Service Program #56.

 

Just one general comment, since OBDII came out in 96 most trouble codes mean the same thing no matter what vehicle it is. that is why all diag connectors are located in the same place and look the same to work even with a generic scan tool.

 

Thanks very much for the information. I am going to go ahead and replace the rear 02 sensor and will look into the potential problem with the mass airflow sensor. You said that you had had some sucess in cleaning the MAS....how do you go about doing so? My service manual indicates that the MAS and IAT are combined on 1999 and later 1.6L DOHC engines. It also outlines testing procedures for the two, or one as the case may be with a combined sensor. I am going to perform the diagnostic tests ( my manual lists a voltage test for the MAS and and ohm check for the IAT) over the weekend (it is my girlfriends car) Assuming I am unsuccessful in cleaning the sensor, do you know of a reasonably priced parts source. In trying to contact a source, Mazdaformance, I saw on the list, the number came back out of service.

Thanks again.

 

I also forgot...I am at 134,000 miles on this machine, but thats for the extended warranty information.

 

I cleaned my MAF by seperating it off the top of the air cleaner box. Then using NON-CHLORINATED brake cleaner, sprayed it all over inside the sensor and it was like a day and night difference. A little trick I learned here on this forum. The tiny little metal piece that measures the air flow is super sensitive.

 

I will get you a picture in the morning of a MAF that you will be looking at so you will be able to see what you are looking at when cleaning.

 

Thanks so much for the responses. This is a great forum and you folks are extremely nice to take the time to respond.

Regards

 

Here are a few pics of the MAF in your car. Marked where the IAT and MAF wires are as best as I could. The most visible one is the IAT. The MAF wires are down inside the sensor as shown with the fuzzy closeup.. If you have a flashlight you will be able to see them fine. There are two separate ones down in there. Those two hidden ones are the most important. Spray them off as well as the IAT very liberally with brake cleaner. Use the little straw that usually comes with as it will allow you to concentrate the spray better. When you first remove sensor, look at the air filter side of the IAT and compare with the engine side. The air cleaner side will probably look gray or black whereas the other side looks clean and shiny. You, of course, want both sides to be clean and shiny.
Let sensor dry for 5 minutes and reinstall. If unable to clean the OE runs around $137.00. Check out www.autoecms.com for prices on remaned or aftermarket.

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Once again... many thanks.

Ervin Maye
Columbia, SC