P0171 Lean Code For Bank 1 Only

[sapforuandme]

2000 Yukon was running ruff. Changed fuel filter, plugs and wires. Runs a lot better, but now has P0171 code for bank one only.

 

5.3 has 140k on it. I was going to change both forward O2 sensors.

 

Any ideas?

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Bad left o2.

bad injector on left side.

bad plug or wire on left side.

I'd start by making sure it's running on all cylinders and not misfiring then move on to replacing the left 02.

[sapforuandme]

I replaced the diverside O2 (the upper one, before the cat).

 

Problem is, Autozone will not clear the codes, they say it is against EPA rules. I have heard that disconnectiong the battery will clear codes on a 2000 Yukon, then others say it will not.

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Them auto zone guys are straight full of shit. NOTHING they can do with an obd2 scanner could possibly be illegal, go somewhere else. And disconnecting the battery for about 10 minutes will reset the codes.

[GDM Z28]

Disconnect both sides of the battery. With the leads off of the battery hold them together (make sure they are NOT connected to the battery) for about 60 seconds. This will clear your light.

 

Instead of just throwing money at the wind I would of swaped front O2's to see if the problem then went to the other bank. If it did not I would spray a very little bit of starting fluid of brake clean around the intake manifold to see if the gasket is leaking.

 

I would not think it would be injectors. For it to be injectors all 4 on that side would have to be weak but still be working which is very unlikely. If it was a bad injector you would more than likely have a lean code (which you have) but it would also be followed by a missfire code.

 

Do you have any friends with decent scanner or any friends that work for a GM dealer? Best thing to do would be put a scanner on it and see what the o2's are actually reading.

[StLouisMO]

I had this situation come up with this same code. It was a vacuum line connected to the brake booster. It was a little loose. This happened after the dealer replaced my Active Fuel Management lifters which required removal of the intake manifold and heads. Evidently the tech knocked a vacuum line loose when putting everything back together.

 

Not saying this is what's happening in your case, but I would check any vacuum lines going to your brake booster.