2003 Yukon issues - SOLVED

[MassHoe04]

Based on what you have shown so far, I like where this diagnosis is heading.
Original hunch on O2 sensors is looking pretty good as possible candidate.

That would be great if this is the case. O2 sensors are relatively easy and not very expensive.

Don't bother doing anything with downstream sensors (B1 S1 or B2 S2) just because you might be in there for the upstreams...
They really don't do anything to affect how the engine behaves. Don't replace unless you get specific codes for them (catalytic efficiency codes).
Save the money for other stuff.

I know AC Delco is preferred on a lot of things, whenever possible. No doubt.
Cost and availability don't always line up with the wallet or having to get the job done so you can get to work the next day.

Delphi O2 sensors and fuel pumps seem perfectly acceptable anytime you can't go with Delco replacements.

For O2 sensors, I replaced both upstream sensors on my 04 5.3L (regular gas) back in November last year.
No issues with the system whatsoever in 10 months of daily driving.

They are normally $55 each, which isn't bad.
I got both for about $88 with the 20% bucket sale.

https://www.napaonline.com/en/search?text=DEN%202344668&referer=v2

I kind of think Delphi might have even been the OEM supplier. They made almost everything else that was electrical on these Chevy trucks...

P.S.: If you ever do need to replace the downstream sensors... They are easy to remember what to get. GM engineers made it easy on everyone by using the exact same sensors in all four positions! My 05 Jeep 4.0L had a different sensor for every position. Part numbers, pigtail lengths... everything was different on each one of those. I had to go to two different shops to get all four sensors for that Wrangler. Thanks for that fun time, Daimler-Chrysler!

 

[ic455]

Ok, update time. I swapped the bank 1 upstream and downstream O2 sensors and ran the truck, even drove down the road with a/c on. Fuel trims normal. O2 data normal. Now trying to tackle what apparently is an unrelated problem: crank, no start. This has been ongoing during this whole operation so I assumed it was part of the running rough. It may not be. Cam and crank sensors are new as well as the connectors for them. Still getting the P0342 and P0343 codes, usually only after it actually starts. When this has happened before, it's dicey if it'll start after sitting a bit or not. This time I ran the battery down and it never did start, this isn't the first time lol.

 

[Fless]

Any time the crank sensor is changed a correlation should be run. Have to rule that out before going further. Might need to reinstall the old one to get it to run and try it with that one if you still have it.

 

[MassHoe04]

Going back a few posts...

Your video of O2 sensor live data doesn't look right to me.
B1 S1 looks like a flatline EKG of someone in cardiac arrest!
If it were a patient, the doctor would be calling for a priest.

B2 S1 looks better. Probably closer to normal wave form and looks reasonable.

If swapping the sensors did nothing, I might suspect something up with the wires or connectors on Bank 1.

Something is up on that side.

Were O2 sensor connectors cut off and replaced with new by any chance?
Maybe wires got crossed on the connector...

I am not ASE certified Mr. Goodwrench, but I don't like what I see on B1 up to this point.
Still points me to believe the flatline on B1 S1 is telling the computer it is not getting enough fuel (low value on the voltage scale indicates too lean), so the computer is just pouring on the fuel to compensate.

You said you changed the PCM, So probably doubtful it is the computer itself.

My gut is still telling me to focus on the B1 S1 O2 sensor, the wires, connectors, connector pins/wires at the PCM or something in between.

 

[ic455]

Going back a few posts...

Your video of O2 sensor live data doesn't look right to me.
B1 S1 looks like a flatline EKG of someone in cardiac arrest!
If it were a patient, the doctor would be calling for a priest.

B2 S1 looks better. Probably closer to normal wave form and looks reasonable.

If swapping the sensors did nothing, I might suspect something up with the wires or connectors on Bank 1.

Something is up on that side.

Were O2 sensor connectors cut off and replaced with new by any chance?
Maybe wires got crossed on the connector...

I am not ASE certified Mr. Goodwrench, but I don't like what I see on B1 up to this point.
Still points me to believe the flatline on B1 S1 is telling the computer it is not getting enough fuel (low value on the voltage scale indicates too lean), so the computer is just pouring on the fuel to compensate.

You said you changed the PCM, So probably doubtful it is the computer itself.

My gut is still telling me to focus on the B1 S1 O2 sensor, the wires, connectors, connector pins/wires at the PCM or something in between.

Swapping B1 S2 into the S1 position cured the trim problem. Now working on intermittent no start. Looking at crank sensor harness as possible cause. Going to trace from sensor to pcm today, will update.

 

[ic455]

When it actually starts and runs, I can't complete CKP relearn; when I'm on "accelerate to full throttle" screen, (fuel cutoff) the fuel never cuts off, I can rev to 6k. Scanner never recognizes "full throttle".

Edit: I had to hold brake pedal while doing relearn, worked this time.‍

 

[ic455]

Update: Still getting P0342 and P0343 and having trouble with hot starts, for now letting it cool for about 20 minutes seems to let it start.

 

[Fless]

Did you clear the codes, and those two came back?

 

[Fless]

Just a SWAG, when you have a hot start issue, floor the accelerator to put it in "clear flood" mode. This turns off the injectors. If it starts right up then there is probably a leaky injector or something else dumping fuel after turning off the engine.

 

[ic455]

Did you clear the codes, and those two came back?

Yes, every time the same 2.

 

[ic455]

Just a SWAG, when you have a hot start issue, floor the accelerator to put it in "clear flood" mode. This turns off the injectors. If it starts right up then there is probably a leaky injector or something else dumping fuel after turning off the engine.

No change if it's still hot. Looks like it has to cool for awhile before it will restart.

 

[Fless]

Should probably verify fuel pressure when hard starting, just to rule it out.

 

[ic455]

SOLVED! Swapped in cam sensor out of my 04 and starts every time. New SKP sensor from rockauto is garbage.

 

[Fless]

Don't you love working back there on those sensors? Glad you got it solved!

Not sure what brand sensor you put in, but it's usually best to bite the bullet and use OE for replacements. Buy once, cry once.

 

[ic455]

Don't you love working back there on those sensors? Glad you got it solved!

Not sure what brand sensor you put in, but it's usually best to bite the bullet and use OE for replacements. Buy once, cry once.

SKF, I think, yeah just a waste of 15 bucks. Thanks for all the input!

 

[ic455]

Thanks everybody for the input!

 

[MassHoe04]

Don't you love working back there on those sensors? Glad you got it solved!

Not sure what brand sensor you put in, but it's usually best to bite the bullet and use OE for replacements. Buy once, cry once.

Agreed on avoiding the bargain sensors.

I would not hesitate to put NTK Camshaft Sensor in, if you can't get OE GM sensor...

More Information for NTK EC0099

$36.79 before any discounts

NTK sensors are actually OE suppliers to many vehicle manufacturers and are generally extremely reliable.

They make great O2 sensors, cam sensors, crank sensors, ABS speed sensors.

I would not think twice about getting NTK for any of those sensors. I have had great experience with their products. I know they are high quality and reliable (never had issues after install). Price is a little better than GM original and available from places that are open longer hours and Sundays, when you can't wait until Monday morning.

The GM was listed as only $8 more and is probably the best option.

Just sayin'... NTK would be the way to go, in my opinion, if GM is not available for you at the time you need it.

 

[mattbta]

SOLVED! Swapped in cam sensor out of my 04 and starts every time. New SKP sensor from rockauto is garbage.

Shop put an off brand one in mine when they did the rear main. Ever since, i've been having weird start issues. I've also had a GM part and intake manifold gaskets ready to go in for a couple months now. Hopefully I'll get around to it soon if this heat lets up.

 

[mattbta]

Finally swapped mine out to OEM and so far no issues! Time will tell.

 

[edward case]

What are the long-term fuel trim values/numbers, and the short-term trims when it goes to closed loop? Is it adding fuel or subtracting?

I'd probably doubt a clogged cat if it has power above idle, maybe set that aside initially.

I had broken pieces of cat plug it on and off as they shifted causing sputtering at higher rom