Code PO174 Bank 2 lean -What does it mean?

[MikDee]

That's the code it's throwin right now, according to my cheap Auto zone scanner. I wish it would go into more detail about what this means? Yesterday it was reading PO142 - Bank 1 sensor 3, not sure which of the 4 sensors this is? but that code's gone now anyway??? Trucks running sluggish as hell, no other symptoms. Help!

[Mikz86TA]

Lean means that there isnt enough fuel on that side. Lean will caus emore heat and could also be the cause of a Cat Conv failure. Bank one is the drivers side O2 giving that code and bank two would be the pass side. Depending on year, you may have one to two downstream O2s as well.
Could be just a random problem, could be a bad injector, etc. Id pull the plugs and see how they look first. Also has it done it B4?

[MikDee]

Thanks Mikz, No codes before? Here's the latest history, been having a problem with hard cold starting for a long time, months ago changed the fuel filter, no help, no difference, then put in new spark plugs, no help, slightly better running no help for the hard cold starts, no other issues with the truck it runs good!,,, got fed up with constant wear, & tear, on the starter, & battery, and put in a new fuel pres regulator a couple wks ago, got the truck together, & running a few days after that, and here it is over a week later, throwing these codes, the 1st one PO142 dissappeared, then I got a PO174, yesterday,,, today I had to go to the Dr. and on the way back the engine light went out? checked it with my scanner when I got home, and the code was still there, I erased it for now.

[bespurcell]

Try running some injector cleaner through it. It can't hurt. Just my 2 cents.

[Mikz86TA]

Year and motor? CPI TBI etc

[MikDee]

Teal 96' GMC Sonoma ext. cab 4.3V6 Auto. 2WD (110k miles) owned about 1 1/2yrs, replaced 1 bad O2 sensor, just before the cat, when I first got it, runs good since, except for hard cold starting for awhile now, requires switching the key, on, & off, a few times to get started, only when cold.

[bespurcell]

Kinda sounds like a fuel pump. I had a car with the same symptoms and that's what it was.

[04silveradomykk]

I had a lean code when I ran a Valve cover breather instead of the crankcase tube off the intake.... the engine pulled a lean code because it was burning unregistered air that wasn't being metered by the Mass Air Flow Sensor

[MikDee]

Thanks for the tips, I'm suspecting the fuel pump, being as I changed the fuel pres reg to no avail, but I can't understand why it's only a problem for the first start of the day?

[bespurcell]

I don't know why either. Mine would usually do it driving down the road. I could turn off the key and turn it back on and it would be fine. Motors are weird. Have you checked fuel pressure?

[MikDee]

I suppose I need to check fuel pressure, but I don't have a gauge, and don't really wanna buy one just for one use. I have read that the fuel pump only runs for 2 seconds to prime when you turn the key on, does that mean it doesn't run when cranking? it just starts again when the engine begins to run? only when oil pressure comes up? I don't get it, how or when, it works?

[Mikz86TA]

No, it just pressurizes the fuel lines until you are cranking it.
Try some autoparts stores. Alot of them have loaner tools for a deposit.
You need to check press for prime, crank and run

[MikDee]

Thanks again Mikz, I erased the code the other day to see what would happen, and of corse it came back last night. So, today when I had some time I went looking to see if anything was amiss under the hood, and found a vacuum line off? It was coming off that plastic vacuum ball under the hood on the drivers side, and laying there open buried from sight on top of the drivers side valve cover, after some hunting around, I found a vacuum diaphram type valve just above where the hose was laying, so I put it back on. I don't know if this was off since I got the truck, or it happened when I recently replaced the fuel pres reg , but the truck seemed to run better when I test drove it, but the light didn't go out so I read the code PO174 again, then erased it, and parked it for the night. I need the truck to run good enough so I can get to town, to shop around for a gauge to borrow.

[Mikz86TA]

Thats the vaccum retention resivoir. Used mainly to aid in the operation of vaccum controlled devices..like AC operations and such. Couldve been an issue

[MikDee]

Had some time today so I decided to go over a few sensors, being as the truck just don't seem to be running quite right yet. I previously erased the code PO174, and it hasn't returned yet. Anyway, once I figured how these things work, I tested the Coolant Temp Sensor, with my compact radio shack digital tester, and all was good, next the Intake Air Temp Sensor, and that turned up good also. I'm not sure how to check the Idle Air Control, don't know if I'll lose any small parts, or knock it out of ajustment if I mess with it? but this truck never went to a high idle start? in the cold weather like most vehicles I've had with fuel injection. I was hoping it was something easy like this but no such luck. I gotta go take a trip into town next, when I get a chance, and see if I can beg a fuel pres gauge to borrow.

[303Radar]

I was periodically getting the same code and managed to get rid of it by cleaning the MAF. I don't remember where I saw the recomendation but it worked for me.

Good Luck

[MikDee]

Thanks radar, will check into that if the code comes back, so far, so good.