o2sensor Bad 02 sensors but only one code pops up

[Andres]

Im new to this mechanic stuff and im not sure wht im doing or how to go about this. I have a 2003 5.3l Silverado. Im using a 2Launch CRP129E scanner and have readings of my 02 sensors. Truck runs like crap, timing is advanced and throttle body says its open at 8%.

Trouble codes are:

P0135

P0449

P0463

 

Any advice? Thanks.

Edited July 9, 2020 by Andres

[Jsdirt]

Would be easier to see if the graphs were separated, but it looks like your downstream sensor is switching - it shouldn't be. That's probably a symptom rather than a cause, though.

 

The last 2 codes I'd disregard for now, since neither will affect drivability (unless your purge valve is stuck open, but that usually throws a leak code too - can try pinching EVAP line off and see if it runs better). The 1st code is just a o2 heater circuit code - that shouldn't cause any drivability issues either once the vehicle is warmed up.

 

What I would do is look at your fuel trims, long and short term (LT, & ST) - any combination into the double-digit percent range, or any single reading in double digits is a problem. You can check your fuel delivery by setting up to graph your MAF, and both upstream o2 sensors, then, go for a 1st gear full throttle run. No need to go 110 MPH - just need to see what the o2's do at full throttle. If they flatline lean, or drop below full rich, you have a fuel delivery issue. If the fuel trims are high at idle, but get better with throttle, you could have a vacuum leak. If the trims are good at idle, but get worse with throttle / load, you probably have a bad, or extremely dirty MAF.

 

Just make sure you've got a sparsely populated area to do the test runs in. Or, a long highway onramp where you can go from 0-75mph.

 

 

Edited July 9, 2020 by Jsdirt

[Doug_Scott]

11 hours ago, Jsdirt said:

 then, go for a 1st gear full throttle run. No need to go 110 MPH

 

I used to get a laugh out of the customers that figured they had to get on the highway to clear the carbon out.  This was back in the days when the throttle was a mechanics tool.  I remember taking a 10 year old Cadillac out for the pre-tune up test drive.  Floored it from 5mph up to 40mph, then let off.  Couldn't see traffic behind me for the white-gray cloud.  I could taste the carbon inside the car.  When I pulled it into the bay the engine was knocking bad.  Ran some water through the vacuum line and that knock went away pretty quick.  Cars with a large load of carbon would every once in a while break off a chuck that would get broken up eventually, the water(actually steam) would help it out the exhaust.  The engine was considerably harder than the carbon.

[Jsdirt]

Used to do the same thing with Japanese sportbikes decades ago. Nothing worked better than water for carbon removal.

 

I had a generator here once that wouldn't start. I thought the engine had locked up. Started checking it out, and I could get about 340° of rotation out of it in either direction - it would stop dead about 10° BTDC. Figured I'd find a valve broken off inside. Saw both springs intact when I removed the valve cover. Hmmm .... removed the head, and found carbon so thick it was stopping the engine! First and last time I've ever seen that. I suspect it was from the unit being run with only super-stale gas.