Motorsteuergerät defekt!? | Posts 16+

Which data point should I read to see if everything is working correctly? By the way, the "ECU fault" error is already triggered when I briefly rev the engine to 4000 RPM in neutral. The intake manifold pressure regulation differential with emergency mode only kicks in at 180, which then corresponds to approximately 4000 RPM.

The MWB,

010, 2, atmospheric, pressure (air pressure)
010,3,Intake manifold pressure (boost pressure),Target value (full load): 1650...2000 mbar

These two values should be approximately the same when the engine is not running.

Best, Chri.

Okay, I just grabbed the laptop and the diagnostic cable and read out the following data blocks, once with the engine off and once at idle.

MWB 3
Motor speed: 0 Motor speed: 903
Air mass: 850
Air mass: 285
Air mass: 1275
Air mass: 285-290
Keyboard input, AGR: 4.8 Keyboard input, AGR: 58

MWB 10
Air mass: 1275
Air mass: 465
Atmospheric pressure: 1193 atmospheres. Pressure: 1153
Intake manifold pressure: 989
Intake manifold pressure: 1010

MWB 11
Motor speed: 0 Motor speed: 903
Boost pressure should be: 194. Boost pressure should be: 1000.
Boost pressure: 989 Boost pressure: 1010
Keyboard input: Boost valve: 99.6 Keyboard input: Wastegate valve: I can no longer read it myself .

I hope that the data will be helpful to you in some way. The left value is always recorded with the engine off, but with the ignition on, while the right value is recorded with the engine running in idle.

Yes.

Based on how I'm interpreting these values, it seems like there's likely a problem with the sensor in the control unit.

Quote:

MWB 10 Air mass: 1275 Air mass: 465 Atmospheric pressure: 1193 atmospheres. Pressure: 1153 Intake manifold pressure: 989 Intake manifold pressure: 1010

I would now say that these two values (bolded) should be very similar, but they are not. Difference > 100 mbar.

The athosph. The air pressure at sea level is approximately 1013 millibars; the pressure decreases with altitude.
In my opinion, this value is too high for you ==> Sensor in the control unit.
The intake manifold sensor provides a plausible altitude reading (approximately 200-300 meters above sea level).

Best, Chri.

Are you referring to the intake manifold pressure sensor or the ambient pressure sensor that is supposedly defective?

The ambient pressure sensor.

Quote:

Based on how I'm interpreting these values, it seems like there's likely a problem with the sensor in the control unit.

Best, Chri.

Okay, that wasn't entirely clear to me, because in my case, both sensors are located in the control unit. I will probably start looking for a different TCU, or I won't drive any faster than 170 .

Alternatively, you could measure the voltage output by the ambient pressure sensor and replace it with a resistor divider to set a fixed value. By experimenting with the resistor divider (or potentiometer), you can then set any desired ambient pressure.

As long as you're not frequently driving in high mountain areas, I don't see any problems. The ambient pressure sensor only reduces the target boost pressure when the air becomes too thin. You shouldn't try to extract maximum power from the engine at very high altitudes.

Regards,
Guste.

I mostly drive around this region, specifically the Ruhr area, the Netherlands, and the Sauerland region, and the problem often occurs when driving uphill.

Then I would save the money that would be spent on a used pressure sensor (STG) and instead set the sensor value to a fixed value, such as 980 mbar, using resistors. However, this is only possible if you (or someone you know) understands what a voltage divider is and how to solder in sensitive electronics.

Regards,
Guste.

Or the sensor signal with a corresponding... Adjust the resistance (in parallel or in series, as needed).

teileklaus wrote:

Or the sensor signal with a corresponding. Resistance (in parallel or in series, as needed).

Hi Klaus,

It's certainly possible in principle. However, I wouldn't trust a malfunctioning sensor too much, as it might drift even further. I suspect it's already producing a non-reproducible output signal, which is why I would replace it completely with resistors. But that's just my personal opinion.

Regards,
Guste.

Dakor, Guste.
If the signal is drifting, what's my version?
If it's unreliable or intermittently incorrect, then it's your version.
Does the sensor output a variable resistance value, or does it provide a voltage?
I'm not trying to be pedantic, just suggesting an alternative. If he's not familiar with voltage dividers, I thought this might be a simpler approach.

teileklaus wrote:

Does the sensor output a variable R value, or does it provide a voltage?

I have no idea. I haven't measured the sensor, nor do I have a datasheet for it. I suspect (!) that it outputs a voltage proportional to the ambient pressure. It could also be a current proportional to the ambient pressure, which is connected to a pull-up/pull-down resistor and goes to the C167. The sensor certainly won't output a variable resistance. Also, given the manufacturing year, I don't expect a digital output signal (PWM, etc.). But as I said: Just my thoughts.

teileklaus wrote:

It's not about being right, [...]

I understood it the same way.

Regards,
Guste.

Since I have absolutely no idea about such intricate soldering techniques, the only solution seems to be to use a different STG (System Terminal Gateway).

Do parts from vehicles like the Sharan, Passat, or Seats with the AFN engine also fit? What about the letters at the end of the part numbers? They are usually different, but the part number has always been the same up to this point.

AFN STG units are quite rare and usually sell for a significant price. The most expensive one sold for €330, but most are in the €120-€150 range. A few weeks ago, I was frustrated that I missed out on an STG unit that was being sold for €75. It had the same registration number and came from the city, just like mine.