Siemens MS43 Retrofit MAP Sensor

From MS4X Wiki

Modern engines are almost exclusively equipped with pressure sensors to measure manifold absolute pressure (MAP).

The M5x engines unfortunately don't have this sensor from factory but that could be very handy when converting the engine to forced induction, or if you simply want to know the pressure of your manifold.

As of today, this sensor is for data logging purposes only, but will be used for additional features in the future. For those who still want to reftrofit a MAP sensor we write this article including a list of parts and tools you need.

Major advantage of this mod is that MS43 actively monitors its +5V supply voltages and uses them as a reference for ADC conversion making it more accurate and fail safe compared to just add an LM7805 inline to +12V.

The manifold absolute pressure sensor used in this tutorial is a Bosch unit that's capable of measuring 20-300kPa and its readily available. This is enough room for up to 2bar (29psi) of boost pressure.

Depending on where you are located prices range from 20€ to $45, so its a cheap mod to do.


  • Crimp tool or soldering iron
  • 0.5mm² FLRy wire (preferably in three different colors)
  • MQS Quadlock pin female for 0.5-0.75mm² wires(Tyco 963729-1)
  • Bosch MAP sensor 20-300kPA (0261230119)
  • Bosch Compact 1.1a connector housing female (1928403966)
  • Bosch Compact series BDK2.8 pins (0.5-1.0mm² 1928498056-L)
  • Seals for BDK 2.8 pins (1928300599)

A) additionally if you chose to solder inside the ECU

  • Torx 15 screw driver to open MS43 case
  • 0.25W 0-Ohm resistor or a short piece of insulated wire

B) additionally if you chose to re-pin the ECU connector instead of soldering

  • Fine screw driver to remove pin from housing
  • MQS Quadlock connector pair with atleast 2 pins
    • 2 pin male: Tyco 1-1718333-1 & female: Tyco 1-968699-1
    • 3 pin male: Tyco 1-1718346-1 & female: Tyco 1-968700-1
  • another short piece of FLRy wire

Create Additional +5V Output

To have an additional +5V output available for the MAP (or RS4 MAF, or basically any other) sensor you need to either modify the ECUs X60004 connector at the wiring harness site, or the ECU itself.

The ECU modification is cleaner and cheaper but involves soldering on the PCB, for the wiring harness mod you have to create a small Y-adapter with a set of MQS connectors but its completely reversible.

From an electronic point of view both mods are equal and bridge the the existing +5V1 supply voltage for the pedal value sensor to the MAP sensor.

If you need additional +5V outputs you can also combine both modifications.

a) ECU PCB Modification

The internal modification of the ECU is pretty easy. The hardest part is propably to find a 0-Ohm Resistor.

  1. Unscrew the four Torx 15 screws at the back and remove the metal ground plate
    MS43 Underside Case.png
  2. Make sure you are facing the backside of the PCB
    MS43 Underside PCB.png
  3. Locate the solder points of X60004 connector in the bottom left area
    MS43 Underside PCB X60004 1.png
  4. Prepare the pins X60004.9 (buttom pin line, second from left) and X60004.6 with some solder
  5. Cut resistor to length and solder it to those two points
    MS43 Underside PCB X60004 2.png
  6. Verify with a multimeter that you didn't short any neighboured pins
  7. Power up the ECU and check the voltage between ground and X60004.6 (+5V)

b) Wiring Harness Modification X60004

Instead of soldering on the PCB you can also create an Y-adapter and splice it between the ECU and the PVS.

Building the Y adapter:

  1. Cut one ~20cm and one ~5cm piece of FLRy wire and strip ~4mm of insulation off both ends each
  2. Splice one of each end together with the other wire
  3. Crimp a male MQS pin to the spliced end first, as this is the hardest part of the mod
  4. Once you've done this you can proceed and crimp another male pin to the short wire and a female to the long wire
  5. Insert both female pins into the housing

That was the difficult part, as you now only have to unpin the +5V wire from the ECU connector and insert the adapter between it:

  1. Unplug the X60004 connector from the MS43 control module (second plug from left)
  2. Remove the connector housing from the grey (1-20) and black (21-40) pin carriers by gently lifting the latches on reach side
  3. Locate the yellow wire on pin X60004.9 and unpin it from the carrier by pressing the latch on top while gently pulling the cable backwards
  4. Now insert this wire to the female MQS connector but DO NOT lock the security lever yet.
  5. Plug the adapters female pin into ECU connector pin X60004.9
  6. Brilliant, you can connect the MAP sensors ground and signal output like the pinout suggest, but instead of X60004.6 you chose any left pin of the Y adapter.

Connection To ECU

  • Sensor Pin 1: X60004.6 +5V Supply Voltage
  • Sensor Pin 2: X60004.5 Sensor Ground (black)
  • Sensor Pin 3: X60004.15 Sensor Signal (black/blue)

Here you can see the finished product with a very short cable length we use for bench testing

MS43 MAP Wiring Harness

Sensor Data