Trouble Codes

[Kountry 2SUM]

So our, new to us, 04 Mountain Aire is spitting codes and when under heavy load losing power. Figured it was a MAF sensor issue or O2 sensor. Here's the codes:

P0151 - Current Fault - O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)

P0131 - Pending Fault - O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)

I'm assuming this is an O2 sensor failure. Is it both O2 sensors or the same one?

[Kountry 2SUM]

Is more information needed?

[vettenuts]

Both banks are giving an error so I would look at a common reason. I would clean the MAF and then see if the codes reappear. Sounds like something is messing up the fuel ratio and the MAF can do this. Plus its cheap to clean. I wouldn't start throwing parts at this problem.

[Arch Hoagland]

Had the exact same problem. Replaced the O2 sensor, no help.

Cleaned the MAF and that fixed it.

Clean your MAF before you do anything else and replace the air filter, do NOT use a K&N.

[Kountry 2SUM]

I went ahead and cleaned the MAF sensor, cleared the codes and will take a test drive when I can. I was wondering though, had it not been for this, the best forum on the planet, I most likely would have spent hundreds replacing O2 sensors that weren't needed, hopefully. Is there a code for the MAF? Or has the OM left to just guess at that one?

Oh yeah, changing the air filter before the test drive too.

[LETMGROW]

Originally Posted by Kountry 2SUM

I went ahead and cleaned the MAF sensor, cleared the codes and will take a test drive when I can. I was wondering though, had it not been for this, the best forum on the planet, I most likely would have spent hundreds replacing O2 sensors that weren't needed, hopefully. Is there a code for the MAF? Or has the OM left to just guess at that one?

Oh yeah, changing the air filter before the test drive too.

This is where a code reader can get someone not experienced in OBD testing into trouble. Going into the data screen with a good quality scan tool will reveal what is really causing your problems. The MAF may be the culprit without setting a code as it isn't out of range enough for the computer to recognize this but the fuel mixture is off enough to flaw the combustion enough to drive the O2 sensors high or low. The data would actually show what voltage the O2 sensors are reading. It is rare BOTH O2 sensors would fail at the same time. It could be the voltage going to the sensors is low or missing. This can be checked with pin point testing with the aid of a service manual and the outlined procedure.
Lynn

[Arch Hoagland]

My 0151 was very intermittent the first year and would only appear when climbing a hill or mountain. One large RV dealer in Fresno looked at it and told me I had to swap out the O2 sensors every couple years and they would do it for only $600.
No thanks....
I bought a new sensor, about $70 and there are a couple varieties, along with a tool to remove the sensor, about $15. Changed the sensor and it didn't help a bit.

Headed from California to Salt Lake City and it got really bad. Got about 20 P0151 and P0131 codes in three days. I had low power and was downshifting all the time.

Got to Salt Lake and took it to a shop on State Street, they cleaned the MAF and I've never had a problem since...and believe me I've been over a mountain or two since then. The power level came right back too.



As LETMGROW said, get a good code reader. I bought the UltraGauge and keep an eye on other things.

[Fred and Bonnie]

Out of curiosity, for those that have needed to clean the MAF, what air filter are you using?

Fred

[Arch Hoagland]

Originally Posted by Fred and Bonnie

Out of curiosity, for those that have needed to clean the MAF, what air filter are you using?

Fred

The first question the shop that I went to asked me was...are you using a K&N air filter.

No. I use a Fram standard air filter.

I used a K&N 30 years ago and discovered I didn't know how to oil it correctly. The K&N will put oil on your MAF and cause problems.

The shop suggested to never use a K&N filter.

[Kountry 2SUM]

Originally Posted by Arch Hoagland

The first question the shop that I went to asked me was...are you using a K&N air filter.

No. I use a Fram standard air filter.

I used a K&N 30 years ago and discovered I didn't know how to oil it correctly. The K&N will put oil on your MAF and cause problems.

The shop suggested to never use a K&N filter.

Yes I agree. Had a similar experience on a two wheeler. High performance racin stuff without computers is about all is use K&N for.

I bought the Wix filter this time and matched it up to the old filter. Didn't think to check which brand the old one was. Wasn't all that dirty. Seemed very clean actually. MAF is all cleaned up and ready to go. Test drive tomorrow, I'll update when I get back.

I was thinking also. There are a number of owners who have experienced water ingestion thus having to change the air filter etc. I installed a Banks Power Pack on our last RV which included a New cold air intake. The Banks "Tuba" had a 1 1/2 to 2" hole on the bottom rear side of the Tuba. That was so that rain water would not be ingested but would fall through the Tuba. Not sure if it would help but maybe punching a 2" inch hole at the lowest point on the workhorse Tuba would help that situation.

Thanks everyone for the advice.

[M&EM]

The factory tuba should already have a drain at its lowest point. It had a flat rubber nipple type of fitting on mine. That might be stuck shut.

[Arch Hoagland]

Originally Posted by M&EM

The factory tuba should already have a drain at its lowest point. It had a flat rubber nipple type of fitting on mine. That might be stuck shut.

Mine stuck shut so I applied some silicone to it.

Can't remember the last time I drove in hard rain so it's not much of an issue for me.

[Kountry 2SUM]

Ok....took the test drive.....east out of ALbuquerque on I40 out to our house in the mountains. 2500 ft. climb in under 20 miles. Was towing a dolly with our Volvo sedan on it. Let it downshift to 3rd several times and no code. Was monitoring the OBD2 with Torque (what a great app) and all components stayed green the entire 25 mile climb.

Thank you guys who steered me to the MAF. Cleaned it, replaced the air filter and were good to go.

[vettenuts]

Glad you got it sorted out and it was a simple fix.