P0155 - Heated Oxygen Sensor Heater Circuit (bank 2, sensor 1)
The P0155 02/03 is the second code set. The P0155 P 03/03 is an additional pending P0155 which is odd.

Bank 2 sensor 1 is the sensor that is located between the exhaust manifold and the 'y' in the y-pipe on the passenger side of the motor.

If you already have new O2 sensors, go ahead and replace both of the upstream sensors. The upstream sensors are the ones closest to the engine exhaust manifolds and are one of the inputs the engine control module uses in determining fuel delivery needs. Your truck may have 2 other sensors, but likely only has one after the catalytic converter. Do not replace the post-cat sensor unless you get a code stating that it is bad and troubleshooting steps have proved that to be the case. The post-cat sensors will not cause driveability concerns when they start to go out like the pre-cat sensors will.

P0101 - Mass Air Flow System Performance

Since this is the first code, that means that it was set prior to the P0155, but given what triggers P0155, I doubt that they are related and, in my opinion, can be handled separately. Most often, this code sets when the MAF sensor has gotten dirty. If your truck has ever had an aftermarket, oiled air filter, the oils used on these filters can gum up the hot-wire sensor bulbs used in the MAF sensor. A little bit of disassembly/cleaning with some sensor safe carbon cleaner (or MAF specific cleaner) and you can sometimes bring them back. If the little sensors inside are really gunked up you sometimes have to lightly scrub them with a q-tip soaked in the cleaner, but be careful. If you break off a sensor wire inside, the MAF will have to be replaced.

Another source of this code could be a vacuum leak in the intake system somewhere between the MAF sensor and the rest of the engine. This can sometimes be a result of a poor seal on the intake 'hat' (the piece that mounts to the top of the throttle body). It could also be a torn/broken vacuum line somewhere in the system. Given that you have an Xtreme, you do not have to worry about the 4wd vacuum system issues that others have to so that simplifies things a bit, but you still have vacuum operated items in the HVAC system, the brake booster, and the vacuum reservoir inside the driver side fender that could have damage. It is fairly easy to visually inspect what's under the hood.

Let us know if you have any questions as well as what you find when you start digging into things.

 

Thank you so much, this was very helpful! Time to dive into it wish me luck, and l'm sure I'll be back with more questions lol. I'll start with the first two sensors and let you know what happens. Thanks again!!!!

 

Hey,
So, just to let anyone know who's interested, I worked all day on my blazer and was unsuccessful changing the sensors out. I lifted the truck and located both upstream sensors. They were easy to find but one is difficult to get to. The wiring was not as easy to get to as all the videos I've watched, next time I raise my truck I gotta lift it higher so I can really get to the clip. However, Unfortunately, both the sensors are stuck and won't budge. So, I ran the engine for 10 min and tried again. I also tapped the socket wrench handle with a hammer and tapped on the 02 sensor itself, after that I was out of ideas. So, I took my truck down, it was getting dark and I need to go buy some spray and just try again tomorrow. I guess PB blaster? I just don't know, if the spray doesn't work, I probably won't be taking a torch to it and will end up needing to pay somebody. I really want to do this myself tho, so any suggestions on getting these stuck oxygen sensors out? Im glad I didn't cut the wires or disconnect anything, because now I can still use my truck. Unless, you can drive without them, but yah. Thats where I'm at. Thanks for reading

 

The only way I ever gotten something freed that's preaty mics welded lol, would be spray it about 30 times over a few hours, then get then hot and a line wrench with a pipe...

good luck... they suck lol... I rather replace the pipe with it...

 

 

 

Congrats... good to hear it finally came out...

 

BTW, nice Blazer Extreme!!! It's good to be very careful about jacking a vehicle and then getting under!! Glad to see that jack stand in the photo.

O2 sensors may or may not fix your problem, but I commend your persistence and that you didn't screw things up getting them out. Be sure to come back if there are still problems. We are here to help people help themselves. You may need to get your own scanner before this is over. If so I can recommend if you have an Android phone. $30-$45 total, depending on the app that you use. BAFX Bluetooth OBD2 adapter as sold on Amazon and Car Gauge Pro app (but Torque Pro or Dash Command might be easier to use for a beginner). Pick your poison. These apps are $5 to $20 max to read most of the GM specific OBD2 Powertrain PIDs (PIDs = Parameter IDs), something the cheap handhelds won't do (they only do the universal OBD2 PIDs). Good luck and best wishes for a successful repair. FYI Torque Pro at $5 is missing an important GM specific PID for Blazers (cam sensor retard), but otherwise is quite good and has a nice interface. You can always add another app later if you need the Cam Sensor Retard PID.

Like Swartlkk said, try cleaning the MAF sensor with MAF Sensor Cleaner for the P0101. Remove the MAF sensor for cleaning and don't touch the wire. And see if that corrects the P0101 problem. Also the Manifold Air Pressure (MAP) Sensor being off can trigger a P0101 (as it is used in the calculation for the test), so you can display that PID on the scanner and make sure the barometric pressure displayed makes sense when the engine is shut off with key on. We can give you approximate values for the MAF sensor at idle and different RPMs, but you would need to have a way of displaying the value your PCM is seeing - again another PID. These two PIDs should be on any scanner device (more than a code reader), as they are universal and not GM specific PIDs. MAF should be around 5 g/sec at idle.

Have you found the OBD2 code descriptions and diagnostics found here: https://blazerforum.com/forum/tech-a...agnosis-26408/

p.s. I see your original post was moved to the new members area by a moderator. You can always click on your name in this forum - then go to statistics to pull up all of your old posts. You did right to start a new thread here in the second gen forum.

p.p.s. You could turn your vehicle around and straddle that dip in the road to give you even more room - but then you would have to lay in the gutter. I've done it before.

 

Good job Abby! I am crushed & amazed with women who know how to successfully turn wrenches. They are like unicorns. I've never meet any here, in Poland.

The bottom of the oil pan / sway bar seem to be wet/oiled. As far as I remember, there is a skid plate underneath, so this shiny substance didn't come from the bottom. If You have it jacked, You may check for the leaks.

Like Les says, getting a cheap BAFX dongle will let You diagnose more accurate and safe Your time & money.