LMM Heat Shield: Check Without Car.

Hi there!
"I have a hot-wire mass flow sensor here, and I applied voltage to it and measured the output. When both protective caps are on, there's already 1.5 volts coming from the output. When I blew on the wire, the voltage increased to over 3 volts."
My question is: Is it normal for 1.5 volts to be output even in "standby mode"?
The LMM is a standard Bosch component without a CO potentiometer.

Deleted upon request.

Sure, you're welcome.
I thought LMM could also stand for "air mass meter."
Actually, the engine in that car is from a Volkswagen Golf VR6.
If it's supposedly normal for it to produce 1.5V even when idling, then it's not useful for me either.

diesel.gustav wrote:

Hello Cord, You're talking about a Bosch hot-wire MAF sensor. To be precise, there's no such thing as a "hot-wire MAF sensor." A hot wire isn't used in a Mass Air Flow (MAF) sensor, which is also known as a throttle air flow meter. But maybe that's just being pedantic. If you have a genuine hot-wire air mass sensor (HFM), then it's from a gasoline engine. It wasn't used in diesel engines. Generally, a Bosch mass airflow sensor (MAF) or hot-wire air flow meter (HFM) outputs a voltage even when no air is flowing. The specific value depends on the sensor and its configuration. When you blow into it, the signal voltage typically increases, as you correctly observed. If you have an HFM5 with reverse flow detection and you blow air in the opposite direction of the intended flow, the signal voltage will decrease; when blowing in the correct flow direction, it will increase. HFMs are currently state-of-the-art technology for diesel engines. A very basic functional test via the signal voltage is possible for each of the sensors mentioned above.