That would clear up some confusion. Thanks. So that will factor in both 02 sensors as a potential problem.

 

Not with a P0171, that wouldn't be a problem with the rear O2 sensor.

 

i was thinking of the forward 02 sensor. I already had the rear changed for another reason.

 

Well I changed the fuel filter and still had the code, but since the filter was original (10 years old) I changed it and I'm glad I did despite the fact it was rusted pretty well on to the line.

I talked to the mechanics at my local Toyota dealer and they said that it would be the MAF so I took their word for it. They were right. No code after a couple of days. They also said that the K&N filter is junk and to get rid of it.

 

x2...

 

Is there a way to easily test the O2 other than resistance? I checked mine against the FSM and they seemed to check out, but I'd like to be more thorough.

 

i have the same problem as OP on my 99 ltd auto v6 i got a CEL a few days ago on the way up the canyon. im taking it to the shop monday morning for a smoke test

 

got a call from the mechanic. said when they smoke tested it, two other codes popped up. so he'll keep checking to see where the leak is. its just time consuming. so i'll have to leave the car at the shop for another day

anybody know what the actual problem was for their rig?

 

Well after changing my 10 year old fuel filter with milky fuel coming out of it, and not fixing the light, It likely won't be that. I would definitely check your MAF. It's 3 12mm bolts and a couple of hoses and your air box comes out. unscrew your MAF and see how much crap is stuck onto the wires. Mine was caked with black dirt, and it was the cause. Clean with electrocontact/MAF cleaner or try that seafoam everyone is talking about. It's a 10min job which I wish I tried first because it would have saved me a few days of work.

 

PO171 bank 1 lean...Tried cleaning with MAF cleaner and I still draw the code. Is there a way to LIGHTLY clean with a Q-tip without damaging the MAF Wires?

 

They way I look at it, is that if it is broke, you can't make it more broke. If you clean with a q-tip, just be prepared to buy a new MAF.

I was looking through the Haynes manual and it says to change the MAF every 80 000KM, which I think is BS. Mine lasted me 200. In either case, I suppose if you have over 80K on your MAF, that it is expected to be changed.

 

well i have this code b4 it was the o2 sensor. yep and those drop in k/n filter are junk it can damnage the hot wire in the air mass sensor. the o2 sensor or expenisve 100 dollar a pop thank god we 3rd gen only have 2

 

got a second opinion from a friends mechanic. he said that 85% of the time with toyotas, its the MAF. if that doesn't work get new o2 sensors.
i looked some up on google.. cheapest is $60 ea.

here:
http://www.partsgeek.com/gbproducts/...ek+Google+Base

 

oil from an oiled air filter was caked on to the MAF wires had to lightly clean large wires with a q-tip dampned w/ MAF cleaner worked like a charm.
NOTE: There ARE TWO small wires consealed in the black tube I MEAN SMALL... and they look like they can be easily damaged ...i didn't dare use a q-tip on these... I JUST SPRAYED w MAF CLEANER...A TON of grime came back out of the tube..reset code and perfect...no code no missing, got my runner back.. nice

 

I was looking at the Underdog Racing Development (URD) Rear Sensor Simulator to address these flaky CEL's. Based on the quote above it seems like this might be a waste of money. any thoughts?

http://www.urdusa.com/index.php?cPat...3j1leudi1qsef5 <---link to URD part mentioned.

 

That will only get rid of a P0420, but it does a great job of doing that.

 

+1 on the URD unit. Works great for me.. Shady as F8Ck but, w/e damn the man

 

I'm having the same code po171 and 306 and I'v replaced the spark plugs, wires, and fuel filter and cleaned and replaced maf sensor. I'm still getting the same codes any ideas what to try next?

 

If all else fails look at the FSM http://www.ncttora.com/fsm/1996/SIL/...e/cip0171p.pdf

 

test injector #6? This is one thing that can cause both codes and is high on the list for troubleshooting both codes.