CEL On Banks 1&2 Lean! help?

[steves99]

My CEL on banks 1&2 lean i need to get this fixed its on a 99 ohv if that helps also. thanks

 

[n0xdw]

Probably lack of fuel pressure. Replace filter and then check the pressure. Refer to the sticky about checking fuel pressure, you need above 60 psi even under load on the 99.

 

[Creager]

...probably one of the hardest problems to find a prognosis for. There really is no single answer to this question as you can have single, simple issue, or a bunch of problems adding up to one massive cluster-****.

Start where the code is pointing: are the o2 sensors telling you that the engine is lean? I wouldnt suspect two sensors going bad at the same time, unless maybe they have been "killed" or contaiminated by combusted coolant. Are you loosing coolant, and not sure where its going?

Check the fuel pressure as stated above. If that checks out, dont rule the fuel system out entirely, contaiminated/stuck injectors are another probable cause. Not sure if your truck has a return fuel system, but this is a canidate aswell.

Vaccum leaks between the maf and throttle, and vaccum leaks around the manifold. Check the integrity of the PCV system: hoses and valve itself.

Also check the ground of the computer to the body. Run a wire from the ground to the battery ground just to see.

good luck.

 

[steves99]

No coolant loss, I will replace the fuel filter and check the presure, thanks for the help guys

 

[steves99]

Anyone else have any ideas

 

[410Fortune]

since both banks are reading lean I would check for leaks in your intake setup.
I would clean my MAS and reset the computer, see if it returns

check fuel pressure

What codes did you pull from the computer?

 

[steves99]

thanks 410 ill try that, another ? would a litlle burping noise coming form the gas cap have anything to do with this?

 

[steves99]

also it had a bad dpsf(sp) sensor a while back i fixed it and the CEL went off for about 2 weeks and then came right back on.

 

[410Fortune]

when the light comes on pull the codes otherwise you have no odea if they are related.

I will tell you to always suspect the last place you worked first

 

[steves99]

when the light comes on pull the codes otherwise you have no odea if they are related.

I will tell you to always suspect the last place you worked first

ok got the codes checked today anyone know what this could be form i changed the fuel filter today

P0171 System too Lean (Bank 1)
P0174 System too Lean (Bank 2)

 

[steves99]

anyone!

 

[n0xdw]

So what was the fuel pressure? Refer to sticky thread if unsure how to check. If it is good going down the road then check/clean the Mass air flow sensor as 410 suggested. That also is a common problem and can cause those symptoms. There are also some threads somewhere about the Mass air sensor.

 

[bigdaawg01]

Check Coolant Temp sensor also..

not sure if the CTS gives a code or not, but it can tell the system to lean itself out because it is reading the wrong temp.. Just a thought