MAP sensor wiring help PLEASE!

[AWE46M3]

Essentially just bypassed the adapter to the MAF harness and wired the IAT directly to the DME pins. Honestly if I had known when I got my airbox, I would have just made my own IAT harness for less and ended up with the same result but less headaches to get to this same point. It's literally two pins and you don't have to modify the factory harness at all. Aka easier to revert back to stock if ever needed.

Turner sells a IAT relocation kit that is marketed for Alpha N that does not have the extra MAF plug in case anyone is looking for that.

[Philom5]

Hi guys, boy has this thread been a great read. I swapped the S54 into my E28 M5 years ago and last year converted to the CSL tune. I run the Kassel MAP kit and it works perfectly. But recently I developed a lean idle condition and also lean at cruise. I'm hitting 17s to 18s at idle and cruise in the high 16s. I have an external wideband installed for AFR monitoring by the way.

So in reading this thread I see that many have used pin 17 for ground rather than pin 16. I'm using pin 16 because it was cleaner, the Kassel kit comes with the connector and you just push it in. But now that I have this lean condition I'm questioning the wiring setup. Datalogging using Testo I'm getting MAP voltage of 3.5V with key on, position 2. MAP pressure is also low, 820 mbar and I'm at sea level. It should be 1000 according to the ECUWorx site. I tested the power and signal voltage in and out of the MAP sensor and get 5V into the sensor from the ECU and 4.1 out of the MAP sensor, signal wire. Pretty normal from what others have posted.

While data logging I looked at the MAF chart and it shows identical reading to the MAP sensor voltage. The MAF plug isn't connected so how in the hell is Testo reading a signal ? Does the CSL firmware use the same MAF circuitry for the MAP sensor ?

Anyway, I'm going to swap grounds and see if it makes a difference. Will post with my findings. Any thoughts please chime in.

Also note, my lean condition flipped one day with no changes to the system. This is the odd part.

Thx.

[Cubieman]

Hi guys, boy has this thread been a great read. I swapped the S54 into my E28 M5 years ago and last year converted to the CSL tune. I run the Kassel MAP kit and it works perfectly. But recently I developed a lean idle condition and also lean at cruise. I'm hitting 17s to 18s at idle and cruise in the high 16s. I have an external wideband installed for AFR monitoring by the way.

So in reading this thread I see that many have used pin 17 for ground rather than pin 16. I'm using pin 16 because it was cleaner, the Kassel kit comes with the connector and you just push it in. But now that I have this lean condition I'm questioning the wiring setup. Datalogging using Testo I'm getting MAP voltage of 3.5V with key on, position 2. MAP pressure is also low, 820 mbar and I'm at sea level. It should be 1000 according to the ECUWorx site. I tested the power and signal voltage in and out of the MAP sensor and get 5V into the sensor from the ECU and 4.1 out of the MAP sensor, signal wire. Pretty normal from what others have posted.

While data logging I looked at the MAF chart and it shows identical reading to the MAP sensor voltage. The MAF plug isn't connected so how in the hell is Testo reading a signal ? Does the CSL firmware use the same MAF circuitry for the MAP sensor ?

Anyway, I'm going to swap grounds and see if it makes a difference. Will post with my findings. Any thoughts please chime in.

Also note, my lean condition flipped one day with no changes to the system. This is the odd part.

Thx.

It's been so long I've forgotten which all wires the MAF uses, I know pin 17 is MAF ground. You may be using some of the MAF wires for IAT or MAP so Maybe that's why you see a reading.

Are you running an Turner IAT harness or is it spliced into the MAF connector or what?

I too have a concerning lean condition, in my 6 years of ownership my first CEL was for "Bank 2 too lean", fortunately I have a WB O2 in that bank.
Last week when I was datalogging just crusing around say 3rd gear 3k while accelerating its damn near around a 15afr wise.

Anytime I really get on it that AFR rises rapidly, it supposedly hit 22 which is scary, I sure hope that is a mistake.
At least it's winter and I won't be driving it much until this is figured out, probably send some logs to the tuner to see what's what.

[Philom5]

Hey !!.., thx for posting. I guess this thread is pretty dam old but deals with my problem perfectly.. .

I'm not running the Turner harness, I used the Kassel CSL conversion kit. They update the ECU and ship it back with a Bosch MAP sensor, IAT sensor and wiring harnesses you wire to the OE harness. I ran mine back to the E28 glove box which is where my ECU lives unlike the E46 chassis. Not a big deal..

So today I was messing around with Testo and looked at a few more data points.

MAP voltage key on - 3.5V
MAP Pressure key on - 877 mbar
Atmospheric Pressure (at ECU) - key on - 1030 mbar

Here's some screen shots.., it's weird how all my values are low. I'm going to look for a local E46 M3 owner that I can pry with drinks and dinner to allow me to tap into their OBD port for some testing. As sort of an A-B test. As a next step though I'm going to check the ECU's main ground. Anyone know where it's located ?

Pic 1 - MAP Pressure Key On (via Testo) Vs the ECU's Environmental reading.
Pic 2 - MAP voltage and Pressure at Idle.
Pic 3 - ECUWorX MAP Voltage pic (For Comparison).

To me everything coming out of my ECU is 20% low. And pic 1 showing what the MAP sensor is reading for atmospheric compared to the internal ECU sensor is baffling.


Thx.