Codes P0137 and P0101
 

Hey guys, my engine light has been been coming on and off for the last couple weeks so I scanned it and got the codes above...

Does anyone have any recommendations on how to fix these?
I'm assuming if I replace the o2 sensor code p0137 will be good but what about p0101? I don't wan't to buy a new MAF sensor if thats not the actual problem.
I tested the harness going to the MAF sensor and its reading 12 volts so i know it's at least getting power.
Also what is the smaller sensor plugged into the air intake? its right next to the MAF sensor...could that be an issue?
Looking for some help so I don't waste money throwing parts at this thing considering I'm trying to sell it soon.

2004 blazer with 85k

thanks, brad

Always fix the lowest numbered code first, as these can cause others to fail. Also, P0137 does NOT indicate a faulty O2 sensor - it indicates that the O2 sensor is reporting a lean condition - nothing more. If it's really lean, replacing the O2 sensor will do nothing.

The other sensor in the intake tubing is the air temp sensor.

P0101 means that the actual MAF sensor reading did not match what the PCM expected for whatever reason. Display MAF in g/sec on your scanner. At idle it should be around 5g/sec. At full throttle should reach around 100g/sec right before transmission shifts. Report your findings please.

Thanks for the reply.. glad I didn't waste money right off the bat by grabbing a new o2 sensor.

I just ordered a new scan tool that should allow me to read live data because the current one I have is a cheapo.

I'll update you in a few days. I should have the scanner by Thursday.

Brad

Ok so I just tested my bluedriver scanner today and so far it seems really cool.

I attached a spreadsheet I made with the live data from the scanner. I slammed the gas from stop and didn't let off until about 70 mph.

The MAF seems to be responding fine. I made two small graphs which helps simplify things. One represents Engine RPM and the other represents MAF Rate (g/s)... both graphs are relative to each other in terms of time.

Take a look at the sheet and let me know what you think.
At this point I'm stumped on where to go next. Could the cats be clogged? or perhaps a vacuum leak somewhere?
Any help is appreciated
Brad

Agreed, the MAF seems to be responding just fine. The way the P0101 code works is the PCM calculates an expected MAF value based on barometric pressure, manifold air temp, and engine RPM. If the actual MAF does not agree with the calculated MAF within some certain set of conditions, then it sets P0101. So if the MAF sensor is OK, then what can it be. It can also be that the inputs the PCM uses to calc the expected MAF value are not working right, or the MAF has an intermittent problem. So the MAP sensor and MAT also need to be checked. You should be able to display barometric pressure using the MAP sensor and your scanner with engine not started - this should agree with weather station. You should be able to display MAT with your scanner. MAT should be ambient before you first start the engine in the AM (this is the other sensor in the intake that you mentioned). And this should be reasonable temps while running. I'm sure you can devise a way to test against a thermometer after engine has been running for some time.

Ok I'm not sure about barometric pressure, the blue driver app I'm using has an option for it however it says it is not supported by my vehicle (of course).. I did another test run reading MAP and intake air temperature.. which I'm assuming is the same thing as MAT that you're referring to?
I didn't make a graph this time but if you compare the engine rpm's to MAP you can see as the rpm's increase so does the MAP. However to be honest I have no clue if the data for MAP is anywhere close to being correct, hopefully you can help me out.
Also the air intake temp fluctuates around 28-30 degrees, which confuses me because the temperature outside is currently 8 degrees. I let the vehicle run for about 15 minutes before I recorded this data so it was up to operating temp. Not sure if that makes a difference.

Could the intake manifold gasket be leaking?

thanks for the response. This is very helpful...
maybe my next steps would be checking the throttle position sensor? Also the vehicle reads engine coolant temperature fine on the cluster and on my scanner, so is it fair to assume that can't be the problem?