Help Needed MAF sensor diagnosis

[drunkenduck]

S40 2001 1.8 petrol B4184S2

Hi everyone,

This is an edited repost, due to misleading title, Apologies if you've already read this

I pulled a P0102 and a P0103 from the car, which has led me to the MAF sensor as, possibly, being the reason for a rough idle/stalls a lot.

Before I get one from the scrapper, I'd be grateful if some more knowledgeable person could confirm that I'm testing it correctly, using my multimeter.

It's a five pin MAF and standing in front of the engine looking down, it's the first on the left (sorry can't remember the wire colours)

Unplugged and ignition on, backprobe reading is 5V, whihc seems ok (?) I believe it should be either 5 or 12.

However, when plugged into the MAF sensor, the voltage drops to 1.78 and remains the same even when I blip the throttle. I've watched this happen with the probe in the back of the plug reading 5V and dropping to 1.78V as soon as it's plugged in.

Would my logic be correct in the assumption that the harness is ok - delivering the voltage - and that the sensor's the problem and it's stuck on transmitting a certain figure to the ECU. The idle goes bad when the engine is warm and will stall all the time - so maybe the ECU thinks the engine is cold all the time.

Any thoughts, as ever,would be much appreciated. Thanks for reading and hope someone can help. Cheers

[bobthecabbage]

It would be good to know the definition of the codes?

I not sure if there are many people left on the forum who would know the test values for a MAF but you may find a general guide if you google it.

It may be on VIDA if anyone is motivated to look it up for you? (I don't have it unfortunately).

I don't know how far you have gone with this but as the MAF measures air flow, you can get errors if you have any splits in hoses or hoses missing or disconnected so its worth thoroughly checking everything.

Especially if any of the codes point to a signal being out of range or implausible.