Po171 And Po440,

[aahn]

PO171 and PO440

My guess is that this is a problem with the MAF sensor

Took it out and the wires "look" dirty but i wouldn't really

know what dirty wires look like... It appears to have some

kind of build up on the middle of both wires but then again

maybe that's how they are suppose to appear...

Could this combination of codes also mean i need to replace

an O2 sensor?

This is for a 2000 RX300 btw

[mehullica]

Clean the MAF with electronics parts contact cleaner to fix the po171. Po440 is an EVAP code. Probabaly a loose gas cap.

[mikey00]

PO440 is also caused by the evap hose coming off the metal tube behind the air filter box directly below the brake fluid container. Did you, or someone else, recently check the air filter and cause this when lifting up on the top of the air filter box?

[AmFam]

The 170 code also comes up when you have a lean bank issue. Like a vacuum leak for example. What happens is the O2 says it is lean as there is much more air than the normal air to fuel ratio. Since the O2 can not determine anything other than a good or bad mix it trips the code saying it is defective or you have a rich or lean bank.

90 percent of the time there is nothing wrong with the O2. It trips due to the reading it is sending to the ECM/PCM.

So do a good look around for a vacuum leak as well..

[Rx330driver]

Im a total noob at cars and i let other people fix things for me, but im just wondering. These sensor warnings you guys are talking about, where do u see them. I mean is there actually a screen on the car that says P0440 error?

[aahn]

no, just a general check engine light comes on and

you use a diagnostic tool to determine what the codes

are and what triggers the light.

i get mine's lent out for free at an advance auto parts.

an update: i cleaned the MAF sensor, the wires were

filthy btw with a non-alcoholic electronics cleaner and

the light went away. I think the response improved

as well.

i'll check the evap too

thanks for the tip