RomRaider

Those fluctuations can be caused by 5V source fluctuations also. In datasheet of 4bar MPX map sensor there is capacitor on the signal line and on the 5v suply also. I'm not telling that 5v suply is the problem but it might be.

Came across this thread in a search for answers and wondering if anyone has experienced something similar. I've wired a GM MAP sensor into rear O2 bank 1. The wiring diagram in this thread seems to have confirmed my wiring is correct and I have confirmed tapping into the correct wires via continuity check between MAP plug and DME plug. I'm getting strange results when logging key on, engine off (I haven't attempted to log with engine running). I'm seeing 3.4V from the MAP sensor at atmosphereic pressure when it should be around 1.6V. I have confirmed this with a multimeter. So, I unplugged the sensor and the logger shows around 4.8V, also confirmed with multimeter. I have rear O2 DTCs disabled, no rear O2 sensors plugged in and all settings selected that allow use of rear O2 for 5V input. Has anyone else experienced something like this? Any reasons why I'm seeing voltage from O2 signal return without anything plugged in? I see it from both rear O2 sensors.

Edit: I also show 4.8V from both primary O2 sensor banks with engine off, including bank 1 I'm using for closed loop feedback. And I log voltage switching back and forth from 0.5V to 4.7V from bank 1 primary during closed loop operation, so I guess that isn't the issue.

Update: For anyone that cares to know or is looking for a solution to a similar problem, I did some testing of the circuit and found using the DME ground, pin 71, was not sufficient. I switched the MAP sensor ground directly to chassis ground and all is working well. Now time to get some logs with boost real time!

Analog inputs float high to around 4.82V in this ECU when unconnected.

Heater ground is PWMed by thr ECU. Don't use this to ground...

Use Signal Ground. Chassis ground can introduce noise/offsets in the measurement.

But it appears people aren't having luck connecting native 0-5V sensors to Signal Ground? Pins 67, 70,71,72. They seem to work fine for WBO2 and Ethanol though?

Has anyone tried the following for MAP wiring?
Use TPS 5V and ground but run signal to one of the O2 inputs?

This should make it easy to make a plug snd play harness.
http://www.bmotorsports.com/shop/produc ... ts_id/3416

My setup is:

+5V from Tank Pressure Sensor (X8000 Splices into TPS +5V fed from the ECU X6000-44)
Signal Input to Post Cat O2 #1 Signal IN (X6000-77)
GND to Post Cat O2 #1 Sensor GND (X6000-71)

Something is not working with this setup, my input floats ~4.8V.
If I check each wire with a multimeter, all seem fine.
Jumping the input pin to GND or 5V works, Using various resistors between power/Input produces a reasonable response.

I've tried multiple MAP sensors. Easiest next troubleshooting step is to try a chassis ground.

measure the output voltage with a volt meter from your map when its connect the way you explained (the sensor ground is on pin 3 from a lambda sensor plug)
I bet its showing 0V because sensor is not active.

redo the same measure with ground on chassis

Cool, we'll figure this out eventually

Also try:
X6000-42 which is a dedicated sensor ground for the TPS.
X6000-40 (X5031-7?) shared sensor ground for FTP sensor and crank angle sensor?
X6000-7 dedicated sensor ground for MAF. But not sure how this is affected by any prior 'bridging of both ground wires in the MAF plug' that I guess some MAFs require.

My Revised setup is:

+5V from Tank Pressure Sensor (X8000 Splices into TPS +5V fed from the ECU X6000-44)
Signal Input to Post Cat O2 #1 Signal IN (X6000-77)
GND to BR/OR Chassis GND Engine Harness Splice (X6459)

X6459 is the large splice of Brown/Orange GND in the engine bay.
No reason I chose this one in particular, other than that I found it quickly visually and in the ETM, and confirmed it went to the strut tower GND on the RHS of the car.

Something about the O2 sensor ground just doesn't work I guess.

No luck here,

I did a few tests after I un-succesfully sent WBO2 and MAP over the post cat O2 locations.
first things first, since that is one that should definitely work.

Wideband analog output from my Innovate SCG-1:
Wired the yellow wire to pin 78 of X6000, with the rest of the SCG-1 wired as normal
https://www.innovatemotorsports.com/sup ... Manual.pdf page 5
Didn't do anything with the signal ground or heater ground pins on the 88 pin connector.

ignition on, engine not started: logging V_rear O2 #2,
Voltage was "pingponging" from 1.44 to 3.73
same while engine was running.

Disconnected the SCG-1 from pin 78, and disabled WBO2 input in my partial.
logging V_rear O2 #2: Same image

I started getting creative with the signal grounds, but after reading more threads, that definitly aint it.

-all post CAT DTC's enabled
-adjusted min and max voltage limits.
-changed catalitic converter efficiency as in discription


ECU is a MS41.0 -681 From an EU 328i, running MS41.3
I'm starting to lose faith that I can use the post cat O2 sensor input's in this ECU?

I was able to wire my WBO2 sensor SCG-1 analog output to the signal of my front O2 bank 2 sensor. Pin 76.

This works.

However, I also want to get MAP pressure wired in. So if I can get this to work on the post cat O2’s that would be great. Any tips?

I have wired WB02 output to pin 76, but in logger voltage for rear sensor stay 1.6V all time. Checking with multimeter it show different voltage(acording to AFR)
ECU is 1429373 converted to MS41.2
Maybe this MCU does not have this input?

MS41.0 hardware does not support Rear O2 sensors as an analog input.
https://sites.google.com/site/openms41/ ... sor-inputs

Pin 76 is for the front O2 bank 2 i believe?
At least, with my MS41.0 I was able to log WBO2 for the past few months,
set it to pin 75 (front O2 bank 1) for WBO2 feedback for MS41.3 at the moment.

I have no answer to Alexduplo's question though,
what have you set for the oxygen sensor's DTC's? maybe that can affect the voltage readings?

Thank you that is what I thought, that MCU of MS41.0 does not have input pins for rear O2
I am going to use front 02 bank2 for log with single O2 configuration

Single O2 Feedback uses Front O2 Bank 1 wiring. Which is the rear plug when looking at the engine bay. Doesn't matter if you're running stock Narrowband or Wideband in Narrowbamd Emulation mode with MS41.3.

Yes I am sure. Remember I already have my car working with a plug and play wideband in Single Channel O2 Feedback and Narrowband Emulation mode since the last couple years with MS41.3.

For single channel O2 put the physical sensor in whichever hole but make sure it's connected to Front O2 Bank 1 wiring...

Stock, the bank 1 sensor is in the front hole on the headers, but connects to the rear plug on the wiring harness near the fuel rail... This is because both sensor cable lengths are the same.... Front sensor can only reach back plug. Back sensor can reach front plug.

Don't confuse the fore/aft locations of the sensor holes versus the sensor electrical plugs.


My schematic shown in the link below is the most correct way to make a PnP harness for your ECU that supports these O2 Sensor Analog Inputs. Please look it over... it provides a separate heater ground for the Wideband O2 controller/sensor as well as dedicated 5V and signal grounds for other sensors.
https://sites.google.com/site/openms41/ ... sor-inputs