P0104 OBD-II Trouble Code: Mass Airflow (MAF) Electrical Circuit Erratic and Irregular Output

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P0104 Trouble code definition

Mass Airflow (MAF) Electrical Circuit Erratic and Irregular Output

  • The Code P0104 code is often associated with a P0100, P0101, P0102 and P0103 codes.

What the P0104 code means

P0104 is the code for issues with the Mass Airflow (MAF) Sensor having inconsistent, erratic or irregular high output voltage/signal to the Engine Control Unit (ECU).

What causes the P0104 code?

The MAF Sensor having erratically high voltage output problems may have several causes:

  • The source of the problem is the sensor voltage is not sending correct voltage output required by the ECU.

  • The most basic problem is too inconsistent high air flow from the air cleaner the MAF sensor.

  • The wiring or MAF sensor may be bad or have a bad electrical connection. It also could be too close to higher voltage consumption components, especially alternators, ignition wires, etc. which would give incorrect signal interference.

  • The air intake system may have a large leak like a bad vacuum hose, air intake hose loose, loose hose clamps or other intake leak before the MAF sensor. The leaks can be cracks that open and close depending on engine speed and loading.

  • MAF sensors must operate within specific ranges to send correct signals for the ECU to adjust correctly for proper engine operation that are compatible with other sensor outputs.

What are the symptoms of the P0104 code?

  • P0104 code will be generally preceded by the Check Engine Light coming on the dashboard display.

  • Normally, the vehicle runs well enough to drive but does require attention.The engine runs close to normal but it may run slightly erratically, have less power, back fire and idle inconsistently higher than normal. Continued driving of the vehicle can cause internal engine damage.

How does a mechanic diagnose the P0104 code?

  • P0104 is diagnosed with an OBD- II scanner. A qualified technician should then reset the OBD- II fault codes and road test the vehicle to see if the code and engine warning light return. He can observe this by watching live data on his scanner while driving. If the code comes back, then the mechanic will need to do a careful inspection to determine if any electrical connector, wiring, sensor, air cleaner, intake and vacuum hoses, loose hose clamps and MAF issues.

  • If no problems are noted, then the next step is to have the technician do a circuit test with a multimeter that has a display to show sampling rate and sensor range voltage readings to determine if the MAF sensor output is really erratically high.

Common mistakes when diagnosing the P0104 code

Diagnostic errors are largely by not following the correct procedure. First, follow the test procedure for the connector, wiring and sensor.

  • Do not buy a MAF sensor unless the other tests indicate no problem and is determined to be bad.

  • Before buying a MAF sensor, try cleaning it with a specialized spray cleaner, like CRC 05110, made for MAF sensors as these often get considerable carbon build up from the emission system, especially at idle.

  • The air intake system may have simple causes like loose clamps, air hoses or vacuum lines, so a close inspection is necessary before buying an expensive MAF unit.

How serious is the P0104 code?

  • The P0104 code will not prevent the car from driving unless the leak is very large.

  • The MAF sensor problem can cause excessive fuel consumption, rough operation and difficulty starting in certain circumstances, or even engine damage if the vehicle is continued to be driven, but it is best to diagnose the problem more accurately.

  • Occasionally, the code can be reset and the vehicle will function normally without the engine warning light or the code returning.

  • Often times, if the engine warning light came on immediately at start up, and the OBD- II system can be reset and the vehicle will operate normally.

What repairs can fix the P0104 code?

The most common repairs to address the P0104 code are as follows:

  • Verify the code with a scanner. Reset the fault codes with the OBD-II Scanner and perform a road test.

  • If the P0104 code and/or engine warning light comes back, then follow the test procedure.

  • Inspect the electrical connector to insure it is attached. Disconnect it and then reinstall to make sure there is a fresh electrical connection.

  • Closely inspect for wiring being frayed or broken on the connector. Repair or replace as necessary before proceeding.

  • Check the air intake system for vacuum leaks, loose hoses and clamps on the intake, especially on older cars.

  • Replace the MAF sensor if no other issues are found.

Additional comments for consideration regarding the P0104 code

Many vehicles with mileage over 100,000 have momentary sensor problems that usually occur during start up or prolonged stress situations on the drive train.

If the engine warning light comes on and the vehicle seems to be operating normally, the OBD-II system can be reset using the scanner and the problem may not reoccur. This is why it is important to verify the fault and reset it before doing any repairs.

Need help with a P0104 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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