StreetFighterZ

I'm currently experiencing problems diagnosing a squirrley A/F ratio sensor. Any help in trouble shooting would be much appreaciated!

Here is the order of events thus far:
-Pulled Code P2a00 (A/F bank 1 sensor 1)
-replaced both bank 1 sensor 1 and sensor 2 (sensor 2 had problems as well, it was stuck and galled as **** upon removal. That's another story)
-Code dissappears (yah!) but voltage outputs still are not at the normal 0.4 V. I decide to ignore the problem in hopes that it goes away


-2 weeks later, the same code appeared (P2a00)
After taking a closer look at the output voltages, the following information was obtained:
Bank 1 Sensor 1 - output hovers around 0.4 V
Bank 1 Sensor 2 - output hovers around 0.9 V

For comparison:
Bank 2 sensor 1 -output typically hovers around 0.9 V

Based on all this information, it seems to me like Bank 2 is running rich and should be triggering a code (which it is not). Bank 1 sensor 1 seems to be operating much more irratically, which to me may indicate a vacumm line leak leading to those cylinders. Anyone have any advice on how to proceed, or what else can be checked? I am using Torque to pull all this information, so knowing if this is a reliable tool for diagnosis would be helpful as well.

StreetFighterZ

After some additional research, it may be relevant to add more history:

The original trigger to this problem was a check engine light indicating burned out cats. Since they were under warranty, I took them straight to the stealership for repair.

The bank 2 upstream and downstream cats were both replaced. I was informed that because bank 1 O2 sensor 2 was "stuck" that the could not replace my cat without me paying for a new sensor. In addition, the new code was P2a00 indicating the upstream A/F sensor was bad. Upon replacement, the code "dissapeared" indicating that the Cat was NOT the problem (i.e. no warranty). I told them to go screw themselves when they told me the price, then promptly replaced the senors myself for 1/5 the price.

Unfortunately I am now experiencing the problems outlined above, with the "bad" O2 sensor obviously not the culprit after replacement. However I realize the dealer is not intelligent enough (or is so intelligent that they know exactly the catch 22 so that they don't have to pay) for replacing the other cat.


This information below is why I am including these details:
"When only one catalyst on one bank has become restricted the typical complaint is a lack of overall engine power. And if the restriction is severe enough miss firing on only one bank and not necessarily on the bank with the defect! This bank isolated miss fire is due to the effects on airflow through the engine with one side of the engine restricted. When one bank is flow restricted the result is less than 50% of the total air entering the engine ends up being passed through the restricted bank. Yet 50% of the fuel mass is still delivered via the injectors to that restricted bank. As a result one bank ends up very lean and the other bank over rich. The first telling sign of an unequal airflow due to restriction on a V-type engine are the fuel trims. If the fuel trims are moving in increasingly opposite directions bank to bank as engine speed and load increase you need to check for a restriction."



Any help on this would be much appreaciated!

Perry690

I have got same problem had bank 1 sensor one displaying fault have changed it few days later ecu fault indicated showing bank 1 sensor 1 took to numerous garages not fault could be found each time warning reset couple of days later back on Have taken to dealership they think it may be bad earth fault when out of dealership now has slip and esp disabled help going back to dealership tomorrow will let you know what happens

myfirstzcar

Check all four sensors again in closed loop and post them please.

StreetFighterZ

I attached readings from the sensors on the CAT throwing the code. During the second half of the readings, I revved the engine and held it at 2000rpm.

These are during closed loop operation.

I wasn't able to capture screen shots of the other side, but they appear to be centered around 0.9 volts, with much less fluxuation from the O2 sensor.

myfirstzcar

Ok, lets forget about the second sensors on each bank for now. All they do is monitor your cats, and should be running at a somewhat steady voltage compared to the upstream sensors.
Your upstream sensors are running at about .4 and .9 correct? You may have an exhaust leak, intake leak, fuel injector and/or pressure issue etc. I wouldn't be suspicious of the O2 sensor at this time.

StreetFighterZ

I agree, unfortunately I just replaced both O2 sensors due to the dealers recommendation. I am currently traveling out of the country (so no access to my car) but I'll be back in a couple weeks to take a look at it.

I purchased propane before I left, so I'll use that to trouble shoot more and post the results here.