P0237 fault. G31 signal too low

[henry0209]

Hi

2019 transporter 150hp diesel dsg

I get the eml light when starting the engine after it has been sitting for some while. Normally it will not light if it's just a short stop.

I read the fault code P0237 via VCDS.

I have tried replacing both map and maf sensor. Also tried wiggeling(?) the wires when engine running and intake air pressure open in advanced measuring values without seeing anything wrong.

Also changed the battery as it was the original since the car was new.

But i still get the eml and faulty start/stop. Engine cooling fan also running high even if engine is not hot after stopping.

Does anybody have any tips or tricks I can try?

When clearing the code after startup, it never shows again until next time I start the engine.

Start/stop does not work tough.

Thanks

 

[mmi]

I have tried replacing both map and maf sensor.

Which sensors exactly?

intake air pressure open in advanced measuring values without seeing anything wrong.

What values you saw exactly?

---

Please post the following

1) Full VCDS Auto-Scan
2) Engine blockmap - Ignition ON/engine OFF
3) Engine blockmap - Engine running at idle

---

How-to create a blockmap file:

[VCDS]
[Applications]
[Controller Channel Map]
- Single Controller Address = 01
- Login or security access code: Leave blank
- Function: Measuring values
- Output: CSV file
[Go]

---

The result (TXT and CSV) files are saved into directory C:\Ross-Tech\VCDS\Logs
Please attach the files here.

---

Post in thread 'Fault code help please'

19 Sep 2021

This one seems give realistic values

IDE07734 Air filter outlet: pressure sensor 1 bank 1: raw value 997 mbar​

Then these two seem to be from same source - actually the same value but different units - the "raw value" probably points to actual sensor. These should show approx. 100 kPa and 1000 mbar even only ignition on.

IDE00594 Absolute intake pressure 37 kPa abs​

IDE07738 Charge air cooler inlet: pressure sensor 1 bank 1: raw value 370 mbar​

I would disconnect (just the electrical plug) the following and check with VCDS the above values and also...

• mmi

• 

 

[henry0209]

Which sensors exactly?


What values you saw exactly?
View attachment 318539

---

Please post the following

1) Full VCDS Auto-Scan
2) Engine blockmap - Ignition ON/engine OFF
3) Engine blockmap - Engine running at idle

---

How-to create a blockmap file:

[VCDS]
[Applications]
[Controller Channel Map]
- Single Controller Address = 01
- Login or security access code: Leave blank
- Function: Measuring values
- Output: CSV file
[Go]

---

The result (TXT and CSV) files are saved into directory C:\Ross-Tech\VCDS\Logs
Please attach the files here.

---

Post in thread 'Fault code help please'

19 Sep 2021

This one seems give realistic values

IDE07734 Air filter outlet: pressure sensor 1 bank 1: raw value 997 mbar​

Then these two seem to be from same source - actually the same value but different units - the "raw value" probably points to actual sensor. These should show approx. 100 kPa and 1000 mbar even only ignition on.

IDE00594 Absolute intake pressure 37 kPa abs​

IDE07738 Charge air cooler inlet: pressure sensor 1 bank 1: raw value 370 mbar​

I would disconnect (just the electrical plug) the following and check with VCDS the above values and also...

• mmi

• 

I wrote a bit fast earlier. I just replaced the pressure sensor sitting on the intake(g31). The one giving the p0237 code.

Absolute intake pressure was steady at about 100kPa when i tried moving and bending the cable to the g31 sensor.


I have attached blockmaps and full scan as requested. I hope it can provide some clues to what`s wrong. Thanks in advance.

Henry

 

[mmi]

Thanks. Unfortunately data from the G31 is just fine in the logs.


Very different in the fault log (below).


So, all I can suggest is a wiring issue somewhere.

I just replaced the pressure sensor sitting on the intake(g31).

This one?

 

[henry0209]

Very different in the fault log (below).

Correct. I only get that low reading from the sensor when starting the engine, and not every time. Mostly after it has been sitting a few hours or more. If I clear the fault code after the engine is running, it never shows again until starting the engine again later. And it runs all fine.

This one?

Yes, that one. Connector looks fine, but its not so easy to follow the cable more than 10-15 cm without disassembling quite a lot.

 

[mmi]

I only get that low reading from the sensor when starting the engine,

Perhaps logging some data while cranking to see if any other sensor data change coincides with pressure drop reading?

Ignition ON

VCDS > Select > 01-Engine > Adv. Meas. Values

Tick the data items

IDE00021 Engine speed​

IDE00018 Voltage terminal 15​

IDE00019 Voltage terminal 30​

IDE00594 Absolute intake pressure​

IDE01834 Battery voltage​

IDE07713 Turbocharger 1 turbine input: temp. sensor 1: B1: raw voltage​

IDE07715 Turbocharger 1 turbine output: temp. sensor 1: B1: raw voltage​

IDE07717 Particulate filter input: temp. sensor 1: B1: raw voltage​

IDE07726 Coolant temperature sensor 1: B1: on cylinder head: raw voltage​

IDE07739 Charge air cooler inlet: press.sensor 1 bank 1: uncnd. voltage​

IDE07808 Fuel temperature sensor 1: B1: before CR pump: raw voltage​

IDE07819 Fuel high pressure sensor: unconditioned voltage​

​

Tick


Log > filename > Start (the logging - IMPORTANT!!!)

Crank/start the engine

Stop (the logging), etc.

---

The result files are saved into directory C:\Ross-Tech\VCDS\Logs

Would be nice to have both good start-ups as well as failed with the fault ones.

 

[henry0209]

Hi, and sorry for the late update.

I have now managed to identify and resolve the issue. I went through several troubleshooting steps, including verifying the wiring, replacing the battery in case low startup voltage was the cause, adding an additional ground cable from the battery negative to the engine block, and disconnecting the intake manifold runner position sensor to rule out interference with the MAP (G31) sensor.

None of these measures solved the problem. In the end, I decided to replace the G31 sensor once more—this time with a genuine Bosch unit (the previous one was from IE Parts).

After installing the Bosch sensor, everything is now working as expected. The start/stop function is operational again, the engine runs noticeably smoother, and the gearbox is now shifting into higher gears more consistently. Overall, it feels like driving a completely different car.

Thank you for your tips and inputs!

 

[manfrotto]

Hi, and sorry for the late update.

I have now managed to identify and resolve the issue. I went through several troubleshooting steps, including verifying the wiring, replacing the battery in case low startup voltage was the cause, adding an additional ground cable from the battery negative to the engine block, and disconnecting the intake manifold runner position sensor to rule out interference with the MAP (G31) sensor.

None of these measures solved the problem. In the end, I decided to replace the G31 sensor once more—this time with a genuine Bosch unit (the previous one was from IE Parts).

After installing the Bosch sensor, everything is now working as expected. The start/stop function is operational again, the engine runs noticeably smoother, and the gearbox is now shifting into higher gears more consistently. Overall, it feels like driving a completely different car.

Thank you for your tips and inputs!

It crops up quite often with non genuine parts unfortunately. ABS wheel sensors are another one where this happens frequently.