Help: Error Code H02s-11, Truck Stalling/losing Power While Driving

pulawman · March 17, 2009

Sorry, but I posted this on other less dedicated forums before finding this one, so this is just a copy and paste job.

Hey guys,

Just got my truck this past Friday (99 Gmc Sierra, 2wd, 5.3, 77k miles). Drove 150 miles back home to shower my parents the truck and Dad noticed it had a pretty bad exhaust leak so we took off the exhaust from the cat back and welded it together. So, fixed the exhaust leak.

Fast forward to today, and on the 150 mile trip back my truck started stalling on me at highway speeds (50-55 mph). It did this 3 times before I made it home. The first time it just lost all power (the motor was still running, but it was hesitating and stomping on the gas did nothing but release a delayed rev on the engine). I pulled over and checked everything out and it seemed fine. So, I pulled back on the highway.

Approx 40 miles later, the same thing. Everything still has power, but I have absolutely no control of the gas and it''s very hesitant and delayed response to pressing the gas pedal.

Approx 20 miles later, the same thing yet again. This time I get a check engine light come one. I''m now approx 15 miles from my apt. I give my dad a call and he seems to think it might be a slipping transmission, but I explain to him that the tranny seems to be shifting firmly and fluently.

I finally get to an Auto Zone right by my apt complex and have them pull the codes. The scanner pulled the code H02S-11 low voltage (heated oxygen sensor bank 1 sensor 1).

- Probable causes:

1. Oxygen sensor defective

2. Fuel system running lean - check other codes first (no other codes)

3. Engine vacuum leak *or* misfire-repair

4. Low fuel pressure-fuel pump defective

I explained the problems to the guy that scanned my truck and he seemed like it would be more probable that my o2 sensors are bad. He said that it would be the o2 sensor before the cat (bank1). He also noted that if the fuel pump was going bad that it wouldn''t pull a CEL (???). I''m going to take it back to the car lot I purchased it from tomorrow to try and follow up on my craptastic 50/50 30 day warranty, but was just wondering what you guys might think the problem might be?

The fuel pump does come on, but when we first got it home it made a high pitch squeling noise. About 10 mins later I check again and it was gone. If though it made this noise it was still coming on. I also check my ATF and it was well within operational levels.

The truck only has 77k on it, so I figured they are probably original O2 sensors and problably need changed anyhow, but I want to try and figure out what the problem might be before the car lot tried to screw me over.

It ran perfectly on the way home sat, and after we fixed the exhaust leak it started running like crap today on the trip back.

Any help will be greatly appreciated and I did use the search function with no results

Thanks,

puLawman

EDIT:

Ok, so a little update. On my way back to the dealer this morn, the CEL(SES)went off. It was only about a 15 minute drive (as opposed to 1.5 hrs)and this morning it is approx 45 degrees out and raining.

The dealer said that they would get it in tomorrow morning and let me know whats wrong with it and how much it's going to be (only got a 30 day 50/50 parts/labor warranty from a used lot). If it's just an 02 sensor and it's going to cost over $100 for them to replace then I will do it in my parking lot myself (Auto Zone quoted me at $72). If it is the fuel pump (I honestly don't think this is the problem) then I will have the shop do it because I'm not even allowed to change my own oil at my apt complex.

I'm still a little upset that this happened 2 days after purchase, but I do believe I got a really good truck. My father even said that the If the 02 sensors were going bad, that the CEL might not have kicked on because of the exhaust leak (any thoughts)?

Ok, so a little update. The shop just called me and said that it was my intake gasket that is bad. Does this sound like a probable cause to the problems I stated in the OG Post?

EDIT: The shop also told me that their scanner actually pulled 4 codes, 2 being O2 codes, 1 being a HVAC for something, and 1 being a MAP sensor code. The actron scanner from Auto Zone only pulled the one code.

Also, is there a possibility that the increased backpressure from the fixed exhaust leak could have caused the intake gasket to go bad?

silveradobobby · March 17, 2009

The intake leaks are real common on these motors it just happened to be the trip you took heated it up and thats all it took also probley sitting in the car lot for a long period of time can dry it out. But that would be giving the codes you stated. FYI an o2 sensor wont cause all those problems! But an intake leak sure will!

minibike132 · March 18, 2009

Check exhaust backpressure, my vote is intermittantly plugged converter. Vehicle ok with an exhaust leak, fixed leak and you describe the tell tale signs of a plugged converter. It wouldn't have shown itself with an upstream leak.

silveradobobby · March 18, 2009

Check exhaust backpressure, my vote is intermittantly plugged converter. Vehicle ok with an exhaust leak, fixed leak and you describe the tell tale signs of a plugged converter. It wouldn't have shown itself with an upstream leak.

Was thinking the same thing! But the leak was from the cat back!

pulawman · March 24, 2009

Check exhaust backpressure, my vote is intermittantly plugged converter. Vehicle ok with an exhaust leak, fixed leak and you describe the tell tale signs of a plugged converter. It wouldn't have shown itself with an upstream leak.

Was thinking the same thing! But the leak was from the cat back!

Ok, so I've been driving my truck since last Wed (after intake manifold gasket was replaced) and everything seemed fine. I even took it out on the interstate this weekend for about 1/2 hr drive after replacing the fuel filter.

Fast forward to tonight.... My CEL came on when I got off work and on my way home. It wasn't stalling/hesitating/bucking like before. So I'm going to try and get it diagnosed tomorrow. It's starting to seem like a chain reaction is happening. Oh well, as long as I get it in tip top conidtion I'll be happy. This is by far the nicest vehicle I have ever owned, and hopefully it'll last me a few years.

I'll post some updates tomorrow if I find anything out.

Any ideas how much it cost to have a GM dealer run a diagnostic scan?