A friend cleaned the MAF sensor after I received this error code. The code went away but came back a short time later. Can I figure that the issue is due to a defective MAF sensor since the light temporarily went away after I had it cleaned, or should I still consider other possibilities? Such as a defective O2 sensor or fuel injector problem, as the print out suggests?

Is it a coincidence that the light came on for the first time the same weekend that I had the spark plugs changed and carbon cleaned out of the intake manifold with a rag and carb cleaner?

Thank you.

 

I don't see a p1071 code listed.... i think you may have mistyped that and it is really p0171...

anyways, most common cause on a Lexus of that code is a mass air flow sensor...

really need a scantool to diagnose this one - you'll want to watch fuel trims... not a bad idea to check for vacuum leaks and check base fuel pressure...

 

90% chance its a bad MAF. The problem with the older MAFs is that the silicone they use to seal the circuit board in the unit eventually melts a bit and leaks into the lower housing, this then gets onto the platinum wires and burns in place.. Cleaning it helps, but the damage is usually done. There is an updated MAF that fixes the problem. If it isnt a MAF problem, which i suspect it is, then you should do as mistuguy suggested.. check for vacuum leaks, etc. I think in the end, you're going to come to the same conclusion.

 

I mistyped the code, it is P0171.

Can a DIYer with basic skill change a MAF sensor? Is it a simple matter to remove and replace it or is there something more to it?

 

that's about as easy as it gets with car repair... on the GS, I don't recall anything in the way... should be two hose clamps, maybe a couple bolts, remove and replace...

nothing special to do in between, though you can take it back to wherever and have the codes cleared, although I think by disconnecting the battery for 5-10 minutes should clear that code as well...

edit: if the codes aren't cleared manually, it may take a week or so for the light to turn off by itself - it will take some time to relearn and adjust and realize everything is back to normal (assuming that fixed it)

 

Could bad gas cause P0171? Is it possible to see if the MAF sensor is damaged if I pull it out?

 

Yes, that is possible. I used to get a P0171 when my RX300 was stock when I lived in Mexico and had to deal with fuel quality issues there.

As far as the MAF sensor, you want to be sure you clean both the red diode and the two wires inside. the sensor shown here. I use CRC MAF sensor cleaner to clean them. They can get black quick.

Also, I don't discount an injector blockage issue (because then air>fuel). For that, I like to use Redline Fuel System Cleaner (costs about $8 USD). If you can't get it, just try a bottle of Techron (any auto parts place, even WalMart has it).

 

Thank you for the reply.

I removed the MAF sensor and see that it is clean to the engine side and blackish to the air filter side. My friend previously sprayed MAF cleaner through the intake opening when I first received the code which should have cleaned the air filter side (he did not remove the MAF when he sprayed it). He reset the codes and the check engine light did not appear for a few days.

Can I get by with a cheaper remanufactured MAF sensor to ge back on the road, or have guys had bad experience with them? I prefer not to spend the money to get OEM unless I am certain that a new MAF will resolve the issue.

I will try fuel system cleaner either way and I will get it properly diagnosed if to clean/replace the MAF.

 

MAFs are pretty stingy especially in Toyota/Lexus products. It's one thing you really want to spend $$$ on, but I'd try some fuel injector cleaner first.

 

The auto parts sites list a MAF Sensor and a MAF Meter. Does this car have both, or is it one or the other? I pulled out what I thought was the MAF Sensor but the part looks like what they refer to as a MAF Meter.

Looks like most sites list the MAF Meter as part number B3130-167313.

Does the Air Mass Meter have issues with the same high frequency that the MAF Senor does?

 

meter / sensor = same thing...