Victory Over Code P0172 Rich!

[Guest]

MAF.pdfAfter 4 days and several trips, I am finally declaring victory over "Code P0172 Rich". This was very irritating because my indy mechanic diagnosed and replaced a weak O2 sensor-$245. Next day, same P0172 Rich code. His response was "well, we can replace this and then that and then...until the code goes away for good". You get the idea. After searching posts on the site I decided to try the low-cost option of cleaning the mass airflow sensor and it appears to have worked! May be a repeat of soemone else but I thought it warranted a picture (attached.)

Here are the steps that go along with the attached picture.

To Clean the MAF sensor:

1. Above is the picture from my 1998 LS400. The MAF is inserted into the air duct just to the right (as you look at this picture) of the air filter.

2. To see if the cleaning in steps 3-4 worked you will need to reset the computer by disconnecting the battery; take the negative lead wire off the battery for 30 minutes. Reconnect the battery after you clean the sensor and put it back in place. It will take a few days of driving to be sure the problem is solved. The Check Engine Light will return if it is another problem or the MAF sensor itself is bad.

3. Take off the MAF sensor. I think it just had a couple of screws holding it into the air ducting. But it took my wife and I working together to get the MAF disconnected from the wires--I held down the clip and she pulled the sensor away from the wire connector. The MAF is itself is about the size of an old 35mm film canister. Inside and to the back are two VERY small wires stretch across the housing that may need to be cleaned. To be honest they were so small I could barely see them and could not see visible debris on the wires.

4. Make sure you are careful not to damage the two small wires of the MAF sensor, and make sure it's dry before reinstalling. I just sprayed canned air into the sensor after spraying the sensor wires with the cleaner then let it sit for about a half hour. I used an electronics cleaner in a spray can from Autozone, about $5. Saw someone say to dip a cotton swab (Q-tip) in the cleaner and then swab the wires but I did not do that because the wires looked so fragile.

I also saw a comment that said, "If a new MAF needs to be installed it is not doable by the shade tree mechanic," but I have no idea why not, it is easily put in but may require settings or something. I don’t even qualify as a shade tree mechanic.

[cardona6569]

Hi: Now that you did that, I would take the connector and clean it with electronic parts cleaner and the sensor probes as well. Then I would seafoam the engine, look in the ES 300 forums on how to. A Throtle valve cleaning is also in order. All easy things to do.

C. PR

[Guest]

Hi: Now that you did that, I would take the connector and clean it with electronic parts cleaner and the sensor probes as well. Then I would seafoam the engine, look in the ES 300 forums on how to. A Throtle valve cleaning is also in order. All easy things to do.

C. PR

Thanks for the advice!

[SKperformance]

Great work , i checked the web for the code and it give maf cleaning as the first possible thing as well as a vacuum problem.

[Guest]

Great work , i checked the web for the code and it give maf cleaning as the first possible thing as well as a vacuum problem.

Yes, wish I had done that first too! I got nervous at the possibility of being stranded and took it straight to my indy mechanic. My other option was to swap out for my 16 year old's '94 Corsica. The thought of having to do that was just too much to bear. I will know to be more patient next time: :)