Error P0104 – how to fix?

P0104 Fault code Definition

Mass Flow (MAF) Electrical Circuit Irregular and incorrect output

• Code P0104 is usually associated with codes P0100, P0101, P0102, and P0103.

What does the code P0104 mean?

P0104 is a code for mass air flow (MAF) sensor problems with an inconsistent, erratic, or irregular high voltage / signal output to the engine control unit (ECU).

What causes the P0104 code?

The MAF sensor has irregular high output voltage problems and can have several causes:

• The source of the problem is that the voltage sensor is not sending the correct output voltage required by the ECU.
• The most fundamental problem is that the airflow from the air purifier to the MAF sensor is too uneven.
• The MAF wiring or sensor may be faulty or have a bad electrical connection. It may also be too close to components consuming high voltage, especially alternators, ignition cables, etc., causing abnormal signal interference.
• The air induction system may have a large leak, such as a damaged vacuum tube, loose air intake tube, loose hose clamps, or other leakage in the air induction system upstream of the MAF sensor. Leaks can be cracks that open and close depending on engine speed and load.
• MAF sensors must operate within specific ranges to send correct signals to the ECU to properly tune engine operation which are compatible with other sensor outputs.

What are the symptoms of the P0104 code?

• The P0104 code is usually preceded by the illumination of the Check Engine light on the dashboard display.
• Usually the vehicle performs well enough to drive but requires attention. The engine runs almost normally but may run somewhat erratically, have less power, flash back and inconsistent idling higher than normal. Continued driving may cause internal engine damage.

How can 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. This can be seen by viewing live data on a scanner while driving. If the code returns, the mechanic will have to do a thorough inspection to determine if any electrical connections, wiring, sensor, air filter, inlet and vacuum lines, loose hose clamps, and MAF problems.
• If no issues are observed then the next step is for the technician to do a circuit test with a multimeter that has a display to show the sampling rate and the sensor range voltage readings to determine if the MAF sensor output is actually erroneously high.

Common errors when diagnosing the P0104 code

• Diagnostic errors are largely due to failure to follow the correct procedure. First, perform the test procedure for the connector, wiring, and sensor.
• Do not purchase a MAF sensor unless other tests indicate that there is no problem and it is faulty.
• Before purchasing a MAF sensor, try cleaning it with a specialized spray cleaner such as CRC 05110, made for MAF sensors, as they often have significant build up of carbon from the emission system, especially when idling.
• The air intake system can have simple causes such as loose clamps, air hoses, or vacuum lines, so careful inspection is necessary before purchasing an expensive MAF unit.

How serious is the P0104 code?

• The P0104 code will not prevent you from driving your car unless the leak is very large.
• A problem with the MAF sensor can cause excessive fuel consumption, rough operation and difficulty starting under certain circumstances, and even damage to the engine if the vehicle is still powered, but it is best to diagnose the problem more thoroughly.
• In rare cases, the code can be reset and the vehicle will run normally without the engine warning lamp or code reappearing.
• Often, if the engine warning light illuminates immediately after starting and the OBD-II system can be reset and the vehicle will operate normally.

What repairs can fix the code P0104?

The most common repairs to fix code P0104 are as follows:

1. Check the code with the scanner. Reset fault codes with OBD-II Scanner and perform road test.
2. If P0104 and / or the engine warning light returns, perform the test procedure.
3. Check the electrical connector to make sure it is connected. Disconnect and reinstall to ensure a new electrical connection.
4. Carefully inspect the connector for frayed or damaged wires. Repair or replace as necessary before continuing.
5. Check the air intake system for vacuum leaks, loose hoses and clamps at the intake, especially on older cars.
6. Replace the MAF sensor if no other problems are found.

Additional notes regarding code P0104

Many vehicles with mileage above 100,000 experience temporary sensor problems, which often occur during starting or prolonged stress on the driveline.

If the engine warning light illuminates and the vehicle appears to be operating normally, the OBD-II system can be reset using a scan tool and the problem may not recur. Therefore, it is important to check the fault and reset it before starting any repair work.