TEST 2: Testing The MAF Signal Key On Engine Running
In this test section, we're gonna check the MAF sensor's output signal with the engine running and make sure that it reacts to changes in engine speed.
Specifically, the MAF sensor's output voltage signal should increase as engine speed increases and decrease as engine speed decreases.
Generally, when the MAF sensor fails, its output voltage will stay stuck in one value regardless of engine speed.
IMPORTANT: The MAF sensor must be connected to its connector to perform this test. You'll need to use a back probe on the connector or a wire piercing probe on the wire. You can see an example of this tool here: Wire Piercing Probe Review (Power Probe PWPPPPP01).
Let's get started:
- 1
Place your multimeter in Volts DC mode.
- 2
Connect the black multimeter test lead to the battery (-) negative terminal.
- 3
Connect the red multimeter test lead to the wire labeled with the number 3 using a suitable tool.
This is the red with green stripe (RED/GRN) wire of the 5-wire connector. - 4
Crank and start the engine and let her idle for about 30 seconds.
- 5
Your multimeter should register 1.1 to 1.5 Volts DC.
- 6
Accelerate the engine by having a helper step on the gas pedal.
- 7
The voltage value should increase as the engine speed increases.
- 8
Decelerate the engine by having your helper step off the gas pedal.
- 9
The voltage value should decrease as the engine speed decreases.
- 10
Repeat steps 6 through 9 several times to make sure of your test result.
Let's see what your test results mean:
CASE 1: The voltage reading increased/decreased as you accelerated/decelerated the engine. This tells you that the MAF sensor is good and is not the cause of the engine performance problem.
CASE 2: The voltage value stayed stuck in one value regardless of engine speed. This usually tells you that the MAF sensor is bad.
If you're diagnosing DTC P0101 MAF Sensor Range/Performance Problem, your next step is to make sure the MAF sensor is getting power. Go to: TEST 3: Making Sure The MAF Sensor Is Getting Power.
If you're diagnosing DTC P0102 MAF Sensor Circuit Low Voltage, you can conclude the MAF sensor is bad if you have:
- Confirmed the MAF signal voltage is 0.1 Volts or less with the key on engine off (TEST 1).
- Confirmed the MAF sensor is getting 12 Volts (TEST 3).
- Confirmed in this test the MAF signal is stuck in one value regardless of engine speed (this test section).
If you're diagnosing DTC P0103 MAF Sensor Circuit High Voltage, you can conclude the MAF sensor is bad if you have:
- Confirmed the MAF signal voltage is 5 Volts or more with the key on engine off (TEST 1).
- Confirmed the MAF sensor is getting Ground (TEST 4).
- Confirmed in this test the MAF signal is stuck in one value regardless of engine speed (this test section).
TEST 3: Making Sure The MAF Sensor Is Getting Power
The MAF sensor needs power, in the form of 12 Volts, to function and produce a viable MAF signal the fuel injection computer can use.
In this test section, we're gonna check that the black with yellow wire (BLK/YEL) wire I've labeled with the number 1 is delivering 10 to 12 Volts to the MAF sensor.
We'll do a simple multimeter voltage test to confirm the presence of this voltage with the key in the ON (II) position (but with the engine off).
IMPORTANT: Be careful not to damage the front of the connector or female terminal with the multimeter test lead, or you'll need to replace the connector.
These are the test steps:
- 1
Disconnect the MAF sensor from its electrical connector.
- 2
Place your multimeter in Volts DC mode.
- 3
Connect the black multimeter test lead to the battery negative (-) terminal.
- 4
Gently probe the female terminal that connects to the wire I've labeled with the number 1 with the red multimeter test lead.
This wire should be the black with yellow stripe (BLK/YEL) wire of the MAF sensor connector. - 5
Turn the key to the RUN position but don't crank or start the engine.
- 6
You should see 10 to 12 Volts on the multimeter.
Let's interpret your test result:
CASE 1: The multimeter registered 10 to 12 Volts. This is the correct result.
If you're diagnosing DTC P0101 MAF Sensor Range/Performance Problem, your next step is to make sure the MAF sensor has Ground, for this test go to: TEST 4: Making Sure The MAF Sensor Is Getting Ground.
If you're diagnosing DTC P0102 MAF Sensor Circuit Low Voltage, your next step is to check the MAF sensor signal with the engine running. Go to: TEST 2: Testing The MAF Signal Key On Engine Running.
CASE 2: The multimeter DID NOT register 10 to 12 Volts. Double check all your multimeter connections and test again.
If you still don't see 10 to 12 Volts, the MAF sensor itself is not at fault as it won't function without 12 Volts.
TEST 4: Making Sure The MAF Sensor Is Getting Ground
OK, so far you have:
- Checked the MAF signal with the key on engine off (TEST 1).
- Checked the MAF signal with the key on engine running (TEST 2).
- Confirmed that the MAF sensor is getting 10 to 12 Volts (TEST 3).
In this last test section, we're now gonna make sure that it's getting Ground from the fuel injection computer.
The wire that delivers this Ground to the MAF sensor is the black with red stripe (BLK/RED) wire I've labeled with the number 2 (see photo above).
Let's get going:
IMPORTANT: Be careful not to damage the front of the connector or female terminal with the multimeter test lead, or you'll need to replace the connector.
IMPORTANT: This Ground is provided by the fuel injection computer internally. Be careful not to connect this wire to battery 12 Volts, or you'll fry the computer. The multimeter voltage test I'm suggesting in the instructions below is a safe way to check for the presence of Ground in this circuit.
These are the test steps:
- 1
Disconnect the MAF sensor from its electrical connector.
- 2
Place your multimeter in Volts DC mode.
- 3
Connect the red multimeter test lead to the battery positive (+) terminal.
- 4
Gently probe the female terminal that connects to the wire I've labeled with the number 2 with the black multimeter test lead.
This wire should be the black with red stripe (BLK/RED) wire of the MAF sensor connector. - 5
Turn the key to the ON (II) position but don't crank or start the engine.
- 6
You should see 10 to 12 Volts on the multimeter.
Let's see what your test results mean:
CASE 1: Your multimeter registered 10 to 12 Volts. This is the correct result and confirms the MAF sensor is getting Ground from the fuel injection computer.
If you're diagnosing DTC P0101 MAF Sensor Range/Performance Problem, you can conclude that the mass air flow (MAF) sensor is faulty if you have:
- Checked the MAF signal voltage with the key on engine off (TEST 1).
- Confirmed the MAF sensor's signal is stuck at one value regardless of engine speed (TEST 2).
- Confirmed the MAF sensor is receiving 10 to 12 Volts (TEST 3).
- Confirmed the MAF sensor is receiving Ground from the PCM (this test section).
If you're diagnosing DTC P0103 MAF Sensor Circuit High Voltage, your next step is to check the MAF sensor signal with the engine running. Go to: TEST 2: Testing The MAF Signal Key On Engine Running.
CASE 2: Your multimeter DID NOT register 10 to 12 Volts. This test result indicates the MAF sensor is not receiving Ground.
Recheck all your multimeter connections and test again. If your multimeter still doesn't read 10 to 12 Volts, you can conclude that the MAF sensor itself isn't faulty as it won't work without Ground from the fuel injection computer.
Your next step is to figure out why this Ground is missing and restore it.
More 2.4L Honda Accord Test Tutorials
If this tutorial was helpful, be sure and take a look at all of the 2.4L Honda Accord diagnostic tutorials in this index:
Here's a sample of the tutorials you'll find there:
- How To Test Misfire Trouble Codes (2003-2006 2.4L Honda Accord).
- How To Test The Engine Compression (2003-2006 2.4L Honda Accord).
- How To Test The Fuel Injectors (2003-2006 2.4L Honda Accord).
- How To Test The MAP Sensor (1993-1996 2.2L Buick Century, Oldsmobile Cutlass Ciera).
If this info saved the day, buy me a beer!
