Guide: Cleaning MAF sensor

[Alphard Club]

This works for both 2.4 and 3.0. This guide is based on the 3 litire model, but you can do the same process with the 2.4. You just need to locate your MAF sensor beforehand. This will be situated after the air Filter box and the engine.

MAF Sensor on the Toyota Alphard - 3.0 V6

What is a MAF sensor?
Your mass air flow sensor or “MAF” detects the volume of air as it enters your engine by heating up a thin wire or resistor. The computer in your car then measures electrical resistance through the MAF as the air flowing through the sensor cools its components down. With a firm understanding of how much air is flowing into your engine, the computer can then direct fuel injectors to add more or less gasoline to the air/fuel mixture.

First off you are going to need a can of Isopropyl Alcohol (excuse the state of my old can  ) Also be weary of buying MAF sensor cleaner. It's the same stuff and it's twice the cost. Go to your local maplin or ebay and purchase a can for around £4

 

You also need a stubby screwdriver. I lost mine so using a short screwdriver.

Unscrew the top housing of the sensor and gently remove.

This will expose the red diode (does not look red at the moment as it's dirty) Spray this diode with Isopropyl liberally.

 

Now for the dodgy bit. Some people recommend not to touch the sensor, however, i have always given mine a very light rub with a cotton wool bud. So be careful here.

 

The dirt is now off the diode.

 

Now look inside the may sensor assembly and you will see two small blades. Give then a good squirt. 

Shake off residual alcohol and wait for the sensor to dry. Takes about 5 mins.

Refit to car.

If you had a Check engine light due to the MAF sensor then this is a good time to disconnect the negative terminal on the battery for 15 mins to reset the ECU and clear any codes. I have seen the car also go in to limp home mode by simply having a dirty sensor.

The dealer hates people knowing how to clean these as most of the time all they need is a simply clean while the dealer wants to help himself to £200 from you for simply replacing a dirty sensor. All Done for just £4 and 15 mins you could say a whole bunch of notes.

 

[Lpgc]

MAF problems seem common on these motors... More common when people have fitted certain brands of paper air filter which seem to leave a bit of a film of dust on the MAF. I've fixed many problems on these engines caused by dusty MAF's. 

Don't confuse the air flow meter part of the MAF unit with the intake air temp part of the MAF unit, there are two sensors (IAT and MAF sensor) inside the MAF housing, a dusty IAT sensor is very unlikely to give problems but the MAF (further inside the unit) does give problems if dusty. 

 

Simon

[gyro]

Excellent article! which there were more of the same quality on this site...

Edited October 23, 2021 by gyro

[Alphard Club]

anyone else managed to cleaned their maf?

[Gamith]

Yes, sort of - I tried but I was unable (the first time) to get the MAF out as it's in an awkward location behind the air-box. So I removed the air filter cover and filter and sprayed the MAF with a load of isopropyl - gave it a good soaking and that was it. I let it dry out and started it some time later (maybe 2 hours) with some difficulty but then it fired and all good, though a little while later the check engine light came back on. 😞

 

So I ordered a replacement part, which turned out to not be a Toyota / Denso stamped part, and fitted it this morning - I was somewhat stumped getting it out and initially thought there were no screws holding it in, but in fact they are tiny cross-head screws, hidden in their recesses and a little fiddly to extract (especially on a cold morning).

However once removed the MAF came out really easily and I put the new part in and started the engine Ok.

I then cleared the fault code (P0171 system too lean on bank 1) and re-read it, it was clear - though the engine light would normally come on after 5 to 30 mins driving so I am not holding my breath.

 

Took about 30 mins for the replacement to be fitted at a guess, though I was faffing around with other stuff such as taking the grill off to retrieve a screwdriver that fell down there.

 

I have attached pictures of the removed MAF and you can see the nice clean side, as well as the not cleaned side. The third picture is the best I could do to show the metal strips inside - obviously the spray didn't get anywhere close to them.

 

As this is now a spare part I will give it a good dosing with the Isopropyl and a go with a swab then put it into stores should I need it.

 

So my takeaway is that the MAF needs to be removed to clean it, otherwise not worth trying to do it through the filter. 

[Picasso]

I have tried a few aftermarket maf sensors Toyotas in general hate them i have always used genuine toyota/denso no issues