Error Code P0104 is defined as MAF (Mass Airflow) Circuit Intermittent. Meaning, the electrical circuit of the MAF sensor produces inconsistent, erratic or irregularly high output voltage signal to the ECU (engine control unit).

This error code is also associated with P0100, P0101, P0103 and P0104.

Definition

MAF sensor is placed in the intake air stream, and its job is to measure the air that enters the, engine while the Engine Control Module uses this information to determine and regulate the correct amount of fuel and ignition timing.

Error Code P0104is triggered when the MAF sensor is malfunctioning or making incorrect airflow readings, as this means a problem with the MAF sensor or circuit.

Common Symptoms

The giveaway symptom for this code is of course, the illumination of the Check Engine light. In terms of drivability symptoms, they’re pretty tricky to spot, and you need to put close attention to the vehicle’s performance, as the engine will run close to normal, and only show slightly erratic performance. Other symptoms include:

  • Less power
  • Inconsistent idle higher than normal
  • Engine back fire
  • Engine hesitates or die
  • Poor fuel mileage

Possible Causes

The most common source of this problem lies in the sensor voltage, when it’s not sending the right voltage output as required by the ECU. And the most basic problem that leads to this trouble code is to inconsistent high air flow from the MAF sensor’s air cleaner. Other causes for erratic high voltage output of MAF sensor can be caused by several causes, such as:

  • Broken, damaged or frayed wire of MAF sensor circuit
  • Corroded or loose electrical terminals in the MAF sensor circuit
  • Air leakage in the intake system
  • Faulty MAF sensor
  • Split or torn MAF sensor intake boot

Also, different makes and models of vehicle will have different leading causes for this trouble code.

How to Check

Diagnosing this code obviously start with the use of an OBD-II scanner. Qualified technicians reset the sensor’s fault codes before taking the vehicle for a road test to see if the code comes back. The technician can observe this through the live data of the scanner while driving.

If the code comes back, the mechanic will then proceed to carefully inspect the components connected to the MAF sensor, from its electrical components, air cleaner, sensor, vacuum hoses, intake, loose hose clamps, and various MAF issues.

If there are no problems in those areas, then mechanic will conduct a circuit test using a multimeter with a display showing the sampling rate and the readings for the sensor range voltage. This is to determine whether output of the MAF sensor is truly erratically high.

How to Fix

  1. As said in the diagnosis, mechanics will conduct a thorough inspection of the wires and connectors for the MAF sensor. To refresh the connection, simply disconnect and then reinstall the connector.
  2. Look for any broken or frayed connectors or wires, repair or replace as needed.
  3. Check the air intake system and look for signs of loose hoses, vacuum leaks and clamps on intake, especially for older vehicles.
  4. Check the MAF sensor’s voltage. You may need to refer to the repair manual for this one to know the specific information for your vehicle.
  5. If you can’t seem to find any other issues causing the problem, then you might need to replace the MAF sensor.

This error code doesn’t really prevent the vehicle from running, unless there’s an extremely large leakage. The MAF sensor however, can cause excessive fuel consumption, difficulty starting and rough operation. Thus, it is important to solve this error code right away, as continued driving with this problem will lead to internal engine damage.

Also, there are cases when the Check Engine light lights up at startup, the OBD-II system can actually be reset to and the vehicle will run normally.