N55 MAF Pinout w/ Voltages

[aspect36]

Hi all,

I picked up a 135i with an N55, which is awesome. However, some rodent decided the MAF wires looked tasty and munched through the wires connected to pins 2, 3, and 4. I managed to repair the harness but am still getting error codes relating to intake air temp being too high on startup and while running. Here is some background info:

- The temp sensor on the MAF itself is physically damaged (it has a small hole in its surface)
- The sensor gives resistance readings of ~400ohms at 30ish degrees C ambient and does decrease in resistance when heated.
- Resistance readings are the same at the sensor plug and the DME ends of the harness.
- Intake air temp as reported by INPA matches ambient temperature readings within 2 degrees upon cold starting. I am assuming this intake air temperature reading is coming from the charge pipe MAP sensor.

Now some questions:

1. What are the voltages supposed to be coming from the DME to the MAF? I've got 12V, 4.85V, and two 0V signals when probed compared to chassis ground.
2. What is the range of resistance values a healthy MAF air temperature sensor would show?

If any of you have actually read all this and have any ideas I would really appreciate the help. A new MAF is coming in on Monday but I'd rather not plug it in and accidentally brick it if my signals are messed up.

Thanks,
Alex

[bbnks2]

Originally Posted by aspect36

Hi all,

I picked up a 135i with an N55, which is awesome. However, some rodent decided the MAF wires looked tasty and munched through the wires connected to pins 2, 3, and 4. I managed to repair the harness but am still getting error codes relating to intake air temp being too high on startup and while running. Here is some background info:

- The temp sensor on the MAF itself is physically damaged (it has a small hole in its surface)
- The sensor gives resistance readings of ~400ohms at 30ish degrees C ambient and does decrease in resistance when heated.
- Resistance readings are the same at the sensor plug and the DME ends of the harness.
- Intake air temp as reported by INPA matches ambient temperature readings within 2 degrees upon cold starting. I am assuming this intake air temperature reading is coming from the charge pipe MAP sensor.

Now some questions:

1. What are the voltages supposed to be coming from the DME to the MAF? I've got 12V, 4.85V, and two 0V signals when probed compared to chassis ground.
2. What is the range of resistance values a healthy MAF air temperature sensor would show?

If any of you have actually read all this and have any ideas I would really appreciate the help. A new MAF is coming in on Monday but I'd rather not plug it in and accidentally brick it if my signals are messed up.

Thanks,
Alex

Newtis.info probably has the info you are looking for. Or INSTA-D/Rheingold.

https://www.newtis.info/tisv2/a/en/e...upply/F7jGcEXP

[aspect36]

Thanks for the suggestions! I stumbled across newtis a few days ago and that website is pretty fantastic. I haven't found voltages listed on it yet but the diagrams helped a ton.
I actually managed to get the MAF temp sensor working today by replacing the thermistor with one from a MAP sensor. A little surprised it actually worked, but it did!