I have an interesting issue in which my '05 H2 runs fine for the first quarter mile, and then I start getting misfires on 1,3,5,7 i.e. all cylinders on bank 1 (driver side) which then throws a p0300. A bit later a p0131 lean condition is added and the bank 1 Ho2S sensor 1 volts fall way below 100mv sometimes even 0.

I originally thought it was a failed sensor sending a lean condition and the truck begins flooding bank 1 with fuel, but I've since replaced that o2 sensor and validated I don't have any circuit issues which means it most likely really is in a lean state; i.e. no fuel to those cylinders?

The service manual is reporting it could be a 1) vacuum leak, 2) incorrect fuel pressure 3) lean fuel injectors, 4) MAF sensor. However, wouldn't you agree that if it's only 1 bank and not the other it could not be 2, 3, or 4 as those would impact both banks; correct?

Thoughts from anyone?

 

intake gaskets are a known failure point. tighten down the intake or replace the gaskets.

 

Check/repair wiring/clean connector to Bank 1 Sensor 1 O2.

 

I've verified the bank 1 sensor 1 component and circuits so I have ruled that out. Also just to follow up, I took it for a test drive and consistently coming out of our neighborhood and cresting above a hill I slowly decrease throttle and this is where my bank1 sensor 1 mv drop to 0. My short term fuel trim jumps to 25%, and then to 54% which is when I begin to experience the rough idle and smell rich exhaust.

 

Very common problem on the H2: Plugged catalytic converter on one side. In your case driver side.

Mine had a very similar problem, same codes, with random cylinder codes all on one side. MAF codes, all sorts of random codes.
A dealer's Tech2 finally showed that the entire one bank was getting the codes, while the other cylinder bank only got a few.
That suggested a plugged cat on that side.

Indeed, turned out to be plugged cat on that side. The OEM replacement is one giant Y-pipe with 2 welded-on cats.
Cost a fortune to replace, but I wanted to stay with OEM.
The vehicle runs like a champ afterwards at 120KPH on steep hills, no problem. Prior to that it struggled on hills.

Best way to tell is to remove (pretty much break them, as they will be seized in) O2 sensors before and after the cat on that side.
Screw in a pressure gauge in the hole. If the pre-cat pressure is very high compared to the post-cat sensor hole pressure, it is a plugged cat.

Plugged cats for some reason are very common on the H2. The ones the factory installed were crap.
My OE replacement has not plugged, but if it ever does again, I will go aftermarket.

Interestingly I took the H2 to 2 dealers, who both said the heads were shot. I did not buy that diagnosis. Went to a third with my suspicion of a plugged cat, and that is what it ended up being.
So careful when you go in, so they do not misdiagnose this. The pressure test is the definitive test, and it will cost you an hour labor + 2 new O2 sensors to find out.

 

I'm fairly sure it's not a clogged cat in my specific case since the bank 1 sensor 1 is very low i.e. under 50mv and the bank 1 sensor 2 is super high; i.e. above 950mv which tells me bank 1 sensor 1 is reporting extremely lean and bank 1 short term fuel trim reads +54% so PCM is dumping fuel in bank 1 and as a result sensor 2 is reporting correctly, i.e. an extremely rich reading after the cat as the cat cannot possibly burn-off +54% fuel trim. The only thing I can think it could possibly be would be another defective bank 1 sensor 1, or PCM.

Otherwise, I just don't see how a vacuum, fuel pressure, or injector problem could result in bank 1 sensor 1 reporting a an extreme lean condition while sensor 2 is reporting an extreme rich condition.

 

if it was not a OEM or same make as OEM sensor it might not be reading correctly. not all oxygen sensor's are created equal. but you should really take a look at your intake gaskets. maybe even do a fuel pressure test to rule out stuck clogged injectors with a injector balance test.

 

How does driving affect the sensor? The sensor is stationary yet the wiring to the sensor is not. It appears there is an issue with the wiring or harness going to the sensor.

 

pull the MAF sensor plug and force the truck to run in Speed Density and see if the issues go away, if they do then its a sensor of wiring issue if not then you have a mechanical issue.

If the truck has no engine mods and is in decent condition it should run fine in sped density

Neal

 

I solved the issue. Reluctantly, I replaced the "known" good bank 1 sensor 1 with a third sensor and now everything is working as it should. The Tech2 clearly showed it had to have been a problem with the sensor, circuit, or PCM. I must have either damaged the "known" good sensor when removing it from an H2 that had no issues OR somehow contaminated it with the anti-seize OR just a complete coincidence that it decided to fail as well.