Seemingly somewhat randomly about every 600-1200 miles, the CeL sets for a lean code. I hadn’t even for sure tracked to see if it’s the same lean code. Using the forum to take note.
2004 LQ4 6.0L
271,661 miles
6/28/24
Ambient temp about 70f, got off I-93 to stop at a gas station in Tilton NH.
Code P0174 - system too lean bank 2
Freeze frame:
2% load
Fuel system closed loop
91C coolant temp
B1 2.3% short term fuel trim
B1 24.2% long term fuel trim
B2 -.8% soft
B2 25% left
Intake map 35.0kPa
660 rpm
Veh speed 17 km/h
Mass airflow from sensor 6.21 g/s
Abs throttle position 0%
2004 G3500 Box Truck CEL
Re: 2004 G3500 Box Truck CEL
Set again tonight 89 min later during a high-load hill climb at the VT property - first gear, floored, temp started to climb.
P0174 - system too lean bank 2
Freeze frame:
Fuel system 1 and 2 closed loop
Load_pct 6.7%
Ect 214 degF
Stft1: -3.1%
Ltft1: 23.4%
Stft2: -.8%
Ltft2: 25%
Map: 14.5 inHg
Rpm 1156
Vss 2 mpg
Maf 2.402 lb/min
Throttle position 12.5%
P0174 - system too lean bank 2
Freeze frame:
Fuel system 1 and 2 closed loop
Load_pct 6.7%
Ect 214 degF
Stft1: -3.1%
Ltft1: 23.4%
Stft2: -.8%
Ltft2: 25%
Map: 14.5 inHg
Rpm 1156
Vss 2 mpg
Maf 2.402 lb/min
Throttle position 12.5%
Re: 2004 G3500 Box Truck CEL
I forget what you did with the MAF. Replace or just clean?
Have you tried disconnecting both O2 sensors? You'd have to get clever to see if that helps since those front sensors drive the fuel trims. But there may be a way to use the rear sensors or perhaps creating a consistent load and looking at injector pulse width before and after unplugging the sensors. All that said it may also just apply the last known fuel trims so the variables may not change when disconnected.
But perhaps my idea is still helpful.
Back in reality I would just do new AC Delco sensors if in doubt. I wouldn't do aftermarket. MAYBE Delphi.
Have you tried disconnecting both O2 sensors? You'd have to get clever to see if that helps since those front sensors drive the fuel trims. But there may be a way to use the rear sensors or perhaps creating a consistent load and looking at injector pulse width before and after unplugging the sensors. All that said it may also just apply the last known fuel trims so the variables may not change when disconnected.
But perhaps my idea is still helpful.
Back in reality I would just do new AC Delco sensors if in doubt. I wouldn't do aftermarket. MAYBE Delphi.
Re: 2004 G3500 Box Truck CEL
Cleaned MAF, codes returned, replaced MAF and has been relatively good since. (Good aside from this issue). I should price O2s on Rockauto
Re: 2004 G3500 Box Truck CEL
P0174 I think 3 times now in 2024. I reset each time and it takes weeks to months to come back.
I should probably borrow a Tech2 to try to exhaustively troubleshoot, but I'm inclined to try a few maintenance parts first (I guess primary 02's are the only thing I can think of...)
Bosch would be about $60 (Internet claims LQ4's were generally Bosch OEM sensors), Delphi $80, $104 GM genuine (I think, upstream/downstream label seems to be wrong on one of the GMs).
I did have the Delphi-debacle for the knock sensors... GM genuine finally sorted it.
https://www.rockauto.com/en/catalog/che ... ensor,5132
I should probably borrow a Tech2 to try to exhaustively troubleshoot, but I'm inclined to try a few maintenance parts first (I guess primary 02's are the only thing I can think of...)
Bosch would be about $60 (Internet claims LQ4's were generally Bosch OEM sensors), Delphi $80, $104 GM genuine (I think, upstream/downstream label seems to be wrong on one of the GMs).
I did have the Delphi-debacle for the knock sensors... GM genuine finally sorted it.
https://www.rockauto.com/en/catalog/che ... ensor,5132
Re: 2004 G3500 Box Truck CEL
Per gmpartsgiant.com it appears to use the same pre/post cat right and pre/post cat left. So just 2 PNs, qty 2 each per vehicle. I'm thinking I should only need the upstream ones.
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Re: 2004 G3500 Box Truck CEL
I would go for GM since you have a nuisance issue.
Re: 2004 G3500 Box Truck CEL
I suppose. Part and service costs on the fleet have been a tad overwhelming. I guess I can either put it off or pony up the $’s. Half-rear cheaping out is probably a mistake.
Re: 2004 G3500 Box Truck CEL
Set the CEL again a couple weeks back - takes a while to reappear since I drive it so seldomly. I waited until about 12 gallons remaining and put in a bottle of techron since it was a lean code. We'll see if that somehow helps or if I need to chase further at some point.