How To Test your Lexus RX330 MAF Sensor

The RX330 MAF Sensor in your Lexus SUV is the centerpiece of your Electronic Fuel Injection system. The MAF sensor is known as the mass air flow meter and it’s a five pin unit that’s mounted into the Lexus intake system. When this RX330 MAF sensor fails on you, or becomes fouled its going to become an issue.

Some of the more common Lexus RX330 issues from a failed mass air flow meter typically include your engine running poorly. Using the input from your airflow sensor and your upstream oxygen sensor, your 3.3 liter Lexus engine computer controls your fuel delivery. It’s aim is to provide for efficient engine operation and maximum fuel efficiency, otherwise known as closed loop operation.

Today I’ll be showing you how to test the MAF sensor in a 2004 Lexus RX330 with a 3.3 liter engine in it. In order to properly test the mass air flow meter, you’ll need to use a digital multimeter.

Some of the more common RX330 issues with your MAF sensor will cause a few problems with your Lexus engine. Here’s a look at some of the symptoms below.

Common Lexus RX330 problems from a bad MAF

• Poor gas mileage
• Smoke from tailpipe
• Engine runs lean (not enough fuel) or rich (too much fuel)
• Bad idle
• Inconsistent throttle response
• Check engine light ON

When your Lexus RX330 check engine light is triggered, you will need to use the correct OBDII scan tool to retrieve the code. Once your scan tool tells you what the stored Diagnostic Trouble Code is, you can begin troubleshooting the part. To begin our DIY tutorial we will test the MAF sensor for power.

Because the mass air flow sensor in your Lexus also houses your Intake Air Temperature sensor, you can use this guide to test the IAT in your 3.3 liter as well.

For starters you will insert your Lexus ignition key and turn to the ON position. Then open your RX330 hood and locate the mass air flow meter. It’s connected to the intake tract and runs directly to your throttle body. To find this part easily, trace back from your air intake box and find the MAF housing.

Testing the RX330 MAF Sensor for Power

Once you’ve got the RX330 MAF sensor unplugged, you can look at the front of the connector. Using the MAF wiring diagram below, you’ll begin testing for power first. Connect the black lead to an engine ground and then gently probe the front of PIN 1 for a 12 volt signal. This is the Lexus power wire for your mass air flow meter.

Now if you’ve got 12 volts at this pin, you can move on to the PIN 2 in our RX330 MAF sensor wiring diagram. This is a ground signal sent from your Lexus engine computer. When testing your mass air flow sensor, never use a ground from your engine harness.

If you have power and ground at these wires, it means that your MAF has what it needs to operate. The next part to this test is to test your Intake Air Temperature sensor. This is an internal part of your Lexus RX330 MAF sensor, and it’s powered through a 5 volt signal that’s at PIN 4.

Making sure you have the ignition turned to the ON position, test PIN 4 for a 4.5 to 5 volt signal. If you have that switched power signal here, move onto the IAT ground signal, which should be PIN 5. The last wire being PIN 3 is the MAF signal, which you can test by backpinning the Lexus RX330 MAF sensor.

Testing the RX330 MAF Sensor Signal

The last leg of our testing guide is to reconnect the mass air flow sensor. Using your multimeter, pierce the wire that leads to PIN 3. Now you need to carefully clear the engine bay, and keep clear of your engine and especially your cooling fans. You would also do well to clear your hands, clothing and tools from your engine, drive belts and pulleys.

Start your engine and monitor the signal from this wire. Once your engine has warmed up the signal should read between .9-1.2 volts of signal at this wire. Slowly increase the engine speed or RPM to 2500 and there you should see between 1.5-1.9 volts of signal.

If your Lexus RX330 MAF sensor does not respond in the following manner, it’s time to remove it and install a replacement airflow meter. Have any questions about this RX330 MAF Sensor testing guide? Leave us a comment below and let us know!