O2 Sensors

snowboarder1988

snowboarder1988

New Member
Jul 10, 2006
27
0
0
California
#1
It looks like I have a bad O2 sensor somewhere. I cleaned them all today and the "service engine soon" light still comes on after a couple minutes of driving. I went to Autozone and ran a diagnostic check and the device said two errors:

Engine too lean (Bank 1)
Engine too lean (Bank 2)

I'm pretty sure that I have some bad O2 sensors. Right? The car runs great and it's not overheating or anything. But I was told that my gas mileage is going to go out the window because the computer thinks the car is too lean, beacuse of the bad O2 sensors. Am I right? Any advice would be great. Thanks!
 

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#2
What were the codes given? Never trust the guys at autozone to diagnose your car. BTW, A lean condition could also be a vacuum leak and I would suspect that, since you are getting lean on both banks (if that is truly what the codes are)
 
#4
snowboarder1988 said:
The codes that were given are these two:

P0171
P0174

P.S. What are Bank 1 and Bank 2? Thanks!
Click to expand...

P0171 System Too Lean (Bank 1)
P0174 System Too Lean (Bank 2)

More than likely you have a vacuum leak. Bank 1 and 2 refer to the cylinders on each side. If I remember correctly Bank 1 is the passenger side, cylinders 1-4, and Bank 2 is drivers side cylinders 5-8.

Have you done any mods recently around your intake or plenum? I would look at the vacuum hoses around the plenum and intake for a loose / broken / or cracked hose.

I really doubt your gonna have two O2 sensors go bad at the same time and fail in such a fashion they screw up the readings that fast to give you lean codes. O2 sensors usually fail slowly over time and you normally get other codes with them first.
 
#5
BTW, these are some of the codes you would normally get when an O2 sensor starts to fail.

P0130 Heated O2 Sensor Circuit Malfunction (Bank 1, Sensor 1)
P0131 Heated O2 Circuit Low Voltage (Bank 1, Sensor 1)
P0132 Heated O2 Sensor Circuit High Voltage (Bank 1, Sensor 1)
P0133 Heated O2 Sensor Circuit Slow Response (Bank 1, Sensor 1)
P0134 Heated O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 1)
P0135 Heated O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
P0136 Heated O2 Sensor Circuit Malfunction (Bank 1, Sensor 2)
P0137 Heated O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)
P0138 Heated O2 Sensor Circuit High Voltage (Bank 1, Sensor 2)
P0139 Heated O2 Sensor Circuit Slow Response (Bank 1, Sensor 2)
P0140 Heated O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)
P0141 Heated O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
P0142 Heated O2 Sensor Circuit Malfunction (Bank 1, Sensor 3)
P0143 Heated O2 Sensor Circuit Low Voltage (Bank 1, Sensor 3)
P0144 Heated O2 Sensor Circuit High Voltage (Bank 1, Sensor 3)
P0145 Heated O2 Sensor Circuit Slow Response (Bank 1, Sensor 3)
P0146 Heated O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 3)
P0147 Heated O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 3)
P0150 Heated O2 Sensor Circuit Malfunction (Bank 2, Sensor 1)
P0151 Heated O2 Sensor Circuit Low Voltage (Bank 2, Sensor 1)
P0152 Heated O2 Sensor Circuit High Voltage (Bank 2, Sensor 1)
P0153 Heated O2 Sensor Circuit Slow Response (Bank 2, Sensor 1)
P0154 Heated O2 Sensor Circuit No Activity Detected (Bank 2, Sensor 1)
P0155 Heated O2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 1)
P0156 Heated O2 Sensor Circuit Malfunction (Bank 2, Sensor 2)
P0157 Heated O2 Sensor Circuit Low Voltage (Bank 2, Sensor 2)
P0158 Heated O2 Sensor Circuit High Voltage (Bank 2, Sensor 2)
P0159 Heated O2 Sensor Circuit Slow Response (Bank 2, Sensor 2)
P0160 Heated O2 Sensor Circuit No Activity Detected (Bank 2, Sensor 2)
P0161 Heated O2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 2)
 
#6
More food for thought, it could be a dirty MAF, need to replace fuel filter, need to replace PCV valve. Just soem more things that will give you those codes. But I would start with looking for a vacuum leak.
 
#7
bad maf, vac leak ( most likey),, low fuel presure... I could go on there is many things that can cause this..

I can tell you for certain that it's not the 02 sensors. As it was said in another post the PCM can tell bogus readings pretty well and will light off different codes other than the bank 1 bank 2 lean codes.

For it to be the sensors the PCM would ahve to be fooled and the sensors would have had to go at the same time..

Start out by checking vacumm lines and air leaks after the maf can cause these codes.

Most likely you will find your problem here.
 
#8
#9
snowboarder1988 said:
I checked the vaccum lines and they all seem OK. Would it have anything to do with the fact that I just installed a C&L MAF Pipe. Also, my airfilter needs to be replaced badly. I have one on order.
Anything look bad in these pictures of my intake:

http://pg.photos.yahoo.com/ph/snowb.../detail?.dir=87a9scd&.dnm=cadescd.jpg&.src=ph

http://pg.photos.yahoo.com/ph/snowb.../detail?.dir=87a9scd&.dnm=4076scd.jpg&.src=ph
Click to expand...

sure that can cause it if somthing was left loose, or you put a different maf in it.. Is it the stock maf? maybe the MAF got damaged durring install?
 
#10
snowboarder1988 said:
I checked the vaccum lines and they all seem OK. Would it have anything to do with the fact that I just installed a C&L MAF Pipe. Also, my airfilter needs to be replaced badly. I have one on order.
Anything look bad in these pictures of my intake:

http://pg.photos.yahoo.com/ph/snowb.../detail?.dir=87a9scd&.dnm=cadescd.jpg&.src=ph

http://pg.photos.yahoo.com/ph/snowb.../detail?.dir=87a9scd&.dnm=4076scd.jpg&.src=ph
Click to expand...

If I were a betting man, something you did during the install is causing your problems. Like SVT said above, something loose or the MAF.
 
#11
Well, I checked it out and everything is tight. The MAF is the stock one and the only thing i changed was the addition of the C&L pipe that the MAF is mounted on. I'll see if the new airfilter helps. If it doesn't, ill put it back to how I had it before and see if that helps. thanks for the help so far. Any other advice is always welcome.
 
#12
did you re-oil the filter before you installed it?

If so, I would start to lean towards a dirty MAF. You want to make sure excess oil from new or newly oiled filters is cleaned off. To clean your MAF, you can CAREFULLY remove it and LIGHTLY wipe it off using a Q-tip and 90% rubbing alcohol. You can also just spray into it using an electronics cleaner (this is the easiest method but I am not sure what type of cleaner to use).
 
#13
MAF's can be very sensitive, try to reinstall the original pipe and reset the keep alive memory ( just disconect the battery for a few minutes since you don't have a scan tool) then see if the codes come back. If not then the sensor is good but the MAF pipe is causing the problem.

I really lean toward the pipe causing the problem
 
#15
The pipe itself shouldn't cause it, but things you do during the installation can. A couple of things in particular, is the clocking of the MAF, and check your ftittings again. If the MAF is not in the same position as it was stock, it will be off. The rubber connectors can sometimes curl up on the bottom of where it hooks to the throttle body wher you can't see it, and let air in. Also check both hoses going to the intake tube.
 
#16
jstreet0204 said:
The pipe itself shouldn't cause it, but things you do during the installation can. A couple of things in particular, is the clocking of the MAF, nad check your ftittings again. If the MAF is not in the same position as it was stock, it will be off. The rubber connectors can sometimes curl up on the bottom of where it hooks to the throttle body wher you can't see it, and let air in. Also check both hoses going to the intake tube.
Click to expand...


sure check all of these things first.. we know it's in the maf pipe at this point there is no sense in taking it off to make sure..
 
#17
also when using an aftermarket pipe or MAF make sure you re-install the screen as it has an O-ring on it that helps seal everything up. how are the O2's? factory, aftermarket? how many miles on them? more than 70k and they could just be at the end of there life span
 
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