Ok so my daughter has this blazer. when driving it will drop down to like 1000 rpms and has no power. you almost think it is dying but it doesnt. you can accelerate through it or it will just correct itself in a few seconds. I scanned it and came up with 2 codes. PO138 and PO140. they come back to O2 sensors. could these cause this symptom? any other guesses?

Thanks in advance!

 

P0138 - HO2S Circuit High Voltage Bank 1 Sensor 2
P0140 - HO2S Circuit Insufficient Activity Bank 1 Sensor 2

Neither of these codes would cause engine performance issues in and of themselves. B1S2 is a catalyst monitoring sensor only and has no impact on the operation of the engine. To diagnose the code, I would swap the pre-cat (B1S2) sensor with the post-cat (B1S3) sensor and see if the codes change to indicate B1S3 is now at fault.

Is the driveability problem intermittent? What are the conditions that cause the issue? When was the last time a tune up was don on the truck (plugs, wires, cap, & rotor)? How about a throttle body, EGR, and/or MAF cleaning?

 

#1 thanks for the quick reply!
#2 I have no idea on the tuneup. I just got it for her. the issues dont seem to happen when the engine is cool. but when driven for 10 minutes or so it happens. seems the more you drive it the more often it happens. you can even have the cruise on and it will happen. you think it has shut off cause the rpms drop down to 1000. almost like maybe starving for fuel. you can give it most of the pedal and it will go away. no engine noise or any bad sounds. but this is not a constant problem. it will do it and then not for a minute or so and then it will happen again.

 

I would check out the state of the parts I mentioned.