Volkswagen Passat: Bad MAF Sensor → Symptoms & Causes - 700R4

The mass airflow sensor (commonly abbreviated to MAF) is one of the most important engine management sensors. A bad mass airflow sensor can leave your Volkswagen Passat’s engine running rough, or even inoperable.

A MAF sensor measures the density of the air entering the intake manifold. It passes this information onto your Passat’s ECU. The ECU uses this information along with other sensor data to control the amount of fuel that enters the combustion chamber.

If you do determine that you need a new mass airflow sensor, they aren’t too expensive. And, most of the time they are right by the air box and easy to replace.

Faulty Mass Airflow Sensor Symptoms: Volkswagen Passat

When the mass airflow sensor has gone bad, you’ll definitely feel it. Here are the most common symptoms of a bad or failing MAF sensor:

• Idle Issues– Your Passat may run rich or lean when idling, or it may also idle erratically. A rich condition is when there is not enough air relative to the fuel in the air/fuel mixture. The exhaust color is usually darker when running rich. A lean condition is when there is too much air relative to fuel in the air fuel mixture. The exhaust color usually doesn’t change.
• Hard to Start– Without knowing the proper amount of air entering into the intake, it can be really difficult for the engine to start. And when it does, it doesn’t usually run very well.
• Jerking– As you go down the road, you’ll feel your Passat really jerk and hesitate as the engine speed changes erratically. It’s bad for your motor mounts when this happens. Also, jerking can be caused by bad spark plugs or coil packs.
• Decreased Fuel Mileage– Fuel mileage can suffer without the proper air/fuel mixture.

Passat Bad MAF Sensor Diagnosis

If the MAF sensor has gone bad, it’ll trigger the check engine light and provide an OBDII trouble code. This is great because it helps you narrow down the problem. The two most common trouble codes in relation to the MAF sensor are:

• Volkswagen Passat P0101 Diagnosis: MAF Sensor
• Volkswagen Passat P0102: MAF Sensor Circuit Low

There are other codes related to the mass air flow sensor as well, but these are the most common ones. Here’s a fantastic video on how to diagnose a bad MAF sensor using a multimeter from Ratchets and Wrenches on YouTube.

Cleaning the Mass Airflow Sensor

Often, the mass airflow sensor really only needs cleaning when they go bad. Some folks recommend using alcohol because it’s usually on hand, and can clean the sensor. This is a bad idea, it can ruin the sensor. Uses mass airflow sensor cleaner. It’s really cheap and available at any parts store. It sure beats the heck out of having to buy a new sensor.

1. Locate the MAF Sensor– It’ll be in between the air filter and the throttle body.
2. Remove the Sensor- Take care not to damage the wiring harness or the connector pins that receive the harness in the MAF. Simple hand tools will be all that you need to complete the job.
3. Clean the Sensor– Now that you’ve removed your Passat’s MAF sensor, it’s time to clean it. You’ll need the MAF cleaner. You are not scrubbing anything. Let the chemicals do their job. About a dozen small bursts will be all that you need.
4. Replace the Sensor

Conclusion

Replacing a bad MAF sensor can make your Passat feel like a new vehicle. Good luck with the diagnosis. If there is anything that you would like to add, please feel free to leave a comment below.

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