cowman79

On my 96 4.6 gt I have gotten a P0172 a couple of times so I started doing some investigating and found that when the engine was running the bank 1 sensor 1 was running around 1% and the bank 1 sensor 2 was running around -100%. I was wondering if this is a downstream o2 sensor problem or something else. I have attached a screen shot of my torque app with the sensor info.



http://i1146.photobucket.com/albums/...ps84499d35.png


Thanks for the help.

cariacou

o2 rear sensor

school boy

P0172 OBD-II Trouble Code

Technical Description

System Too Rich (Bank 1)

What does that mean?

Basically this means that an oxygen sensor in bank 1 detected a rich condition (too little oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1.

Note: This DTC is very similar to P0175, and in fact your vehicle may show both codes at the same time.

Symptoms

You will more than likely not notice any drivability problems, although there may be symptoms such as a misfire.

Causes

A code P0172 may mean that one or more of the following has happened:
•The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
•There could be a vacuum leak.
•There could be a fuel pressure or delivery problem

Possible Solutions

Possible solutions include:
•Inspect all vacuum and PCV hoses, replace if necessary
•Cleanthe MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
•Inspect fuel lines for cracks, leaks, or pinches
•Check the fuel pressure at the fuel rail
•Check the fuel injectors, they may be dirty. Use fuel injector cleaner or get them professionally cleaned/replaced.
•Check for an exhaust leak before the first oxygen sensor (this is unlikely to cause the problem, but it is possible)

cowman79

I have seen the same troubleshooting guide before. I have cleaned my mass air sensor and the light came on about a week later. That is why I got the Bluetooth code reader to try and get some better data for troubleshooting. I am now leaning towards the bank one sensor 2 oxygen sensor because of the way it is reading on the live data screen shot.

school boy

Well the reason I posted that is to do the small cheap things first. Im leaning towards a o2 sensor myself but I always like to check the small things first.

art02gt

rear o2 sensors only monitor cat efficiency and have nothing to do with the engine running rich or lean. you have a rich condition which means you either have too much fuel or not enough air. I wouldn't throw parts at it yet, the first thing I would do is check for vacuum leaks (pcv hoses, intake gaskets etc.).

cowman79

If I have a rich condition then why isnt the bank one sensor 1 showing a high reading. If both sensors are in the same gas stream then wouldnt they both have similiar readings.

art02gt

what you posted are fuel trim readings. o2 readings are in volts.

cowman79

Wouldn't the fuel trim be derived from the o2 rreading. If all of the other fuel trims are around 0 then wouldn't the problem have something to do with that banks sensor 2.

art02gt

fuel trims are calculated and adjusted from the upstream o2 sensor, not the rear.