TEST 1: Checking The MAF Sensor Power Circuit
To get our MAF sensor diagnostic on its way, we'll make sure that it's getting power.
This power comes in the form of 12 Volts and is provided with the Key On Engine Off (KOEO) and Key On Engine Running (KOER).
The wire that's responsible for feeding this voltage to your Toyota's MAF sensor is the wire labeled with the number 1 in the photo above.
NOTE: You can use a 12 Volt automotive test light or a multimeter to confirm wire #1 is feeding 10 to 12 Volts to the MAF sensor. Although the test instructions below assume that you'll be using a multimeter.
OK, this what you'll need to do:
- 1
Place your multimeter in Volts DC mode and unplug the MAF sensor from its electrical connector.
- 2
Connect the red multimeter test lead to the wire labeled with the #1 in the photo above.
The #1 wire is the black (BLK) wire of the MAF sensor's connector.
NOTE: Avoid probing the front of the female terminal (of the MAF sensor's electrical connector). - 3
Connect the black multimeter test lead to the battery negative (-) terminal.
- 4
Turn the key on but don't crank or start the engine.
- 5
Your multimeter should read 10 to 12 Volts DC if the connector's wire is supplying the MAF sensor with power.
Let's analyze your test results:
CASE 1: The multimeter recorded 10 to 12 Volts DC. So far so good, since this test result tells you that your Toyota's mass air flow (MAF) sensor is getting power.
The next step is to make sure that the MAF sensor has a good Ground in the wire labeled with the number 2. For this test, go to: TEST 2: Checking The MAF Sensor Ground Circuit.
CASE 2: The multimeter DID NOT record 10 to 12 Volts DC. Make sure that you're testing the correct wire, that your connections are OK, and repeat the test.
If your multimeter still doesn't register between 10 to 12 Volts, then you've found a problem that needs to be corrected. Without these 10 to 12 Volts, your Toyota's MAF sensor won't work.
TEST 2: Checking The MAF Sensor Ground Circuit
In TEST 1, you confirmed that your Toyota's MAF sensor is getting power. Now you need to make sure that it's also getting Ground.
This Ground is provided by the wire labeled with the number 2 in the photo above.
You can check this Ground with a 12 Volt automotive test light or a multimeter. The test instructions below assume that you'll be using a multimeter.
NOTE: This Ground is provided directly by your Toyota's fuel injection computer, so be careful and don't short this wire to battery 12 Volts or you'll fry it.
OK, these are the test steps:
- 1
Place your multimeter in Volts DC mode and unplug the MAF sensor from its electrical connector.
- 2
Connect the black multimeter test lead to the wire labeled with the #2 in the photo above.
The #2 wire is the blue with white stripe (BLU/WHT) wire of the MAF sensor's connector.
NOTE: Avoid probing the front of the female terminal (of the MAF sensor's electrical connector). - 3
Connect the red multimeter test lead to the battery positive (+) terminal.
- 4
Turn the key on but don't crank or start the engine.
- 5
Your multimeter should read 10 to 12 Volts DC if the connector's wire is supplying the MAF sensor with Ground.
Let's interpret your test results:
CASE 1: The multimeter recorded 10 to 12 Volts DC. This multimeter test result tells you that the MAF sensor on your Toyota is getting a good Ground.
The next step is to make sure that the MAF sensor is working and outputting a MAF signal on the wire labeled with the number 3. For this test, go to: TEST 3: Checking The MAF Sensor Signal.
CASE 2: The multimeter DID NOT record 10 to 12 Volts DC. Make sure that you're testing the correct wire, that your connections are OK, and repeat the test.
If your multimeter still doesn't register voltage, then you've found a problem that needs to be corrected. Without this Ground, your Toyota's MAF sensor won't function.
Repairing this Ground issue will get the MAF sensor back on its feet.
