Quantity Setting Error: N146 Upper Limit Reached

Dear Volkswagen Golf TDI owners,

I'm having the following problem (engine: ALH, 66 kW, 90 hp, 356,000 km, rotary injection pump).
When starting the warm engine (relatively often, about 32-40% of the time), and very rarely when starting the cold engine, I get a "flashing glow plug" symbol and a beeping sound with the error message "Engine fault - workshop."
I've been experiencing this issue since last summer.
The following information is stored in the error memory: 17970 - Quantity adjuster (N146), upper limit value exceeded, intermittent.

Otherwise, the error has no effect; there's no stuttering, good acceleration, and everything feels perfectly fine.

"About 3 years ago, I experienced some jerking when slowly decelerating. Because a "stiff fuel distributor control unit" (MSW of the VP 37 injection pump) can also be responsible for this, I thoroughly cleaned the MSW at that time. However, this was not the cause of the jerking; the problem was a faulty dual-mass flywheel."
After cleaning, I reset the control unit in the MSW using VCDS to the original value it had before cleaning (0.74V).

"Because I recently thought I detected a connection between air in the diesel line and the MSW fault (I saw some bubbles in the line), I replaced the diesel filter and the fuel filter valve (also known as the "knackfrosch"). The air in the line has now disappeared."
And now I also think I'm noticing that the error occurs less frequently, although this may be subjective.
There are also online resources regarding error code 17970 and air in the diesel fuel line. According to these descriptions, air is more likely to escape from the MSW (presumably a component or system) when driving uphill. I tested this tip about driving uphill, but the results were not conclusive. However, the error occurs very rarely after a steep uphill climb, although it hasn't completely disappeared. And the error reappears after a while, even though there is no apparent air in the fuel line.

Do you have any more suggestions or tips for me?
Is the VP37 injection pump simply reaching the end of its lifespan (356,000 km) when used with an MSW system?

Thank you very much.
Greetings.
TDI driver.

The error can probably be fixed by readjusting the valve lifter (even though the 0.74V reading looks good).
Bleed valves are more of a myth than anything else.
Would you consider doing an Autoscan? We'd like to see a reference to the economic foundation of this forum in such topics, so ideally something from VCDS, the operator of the forum.
hg
Herbert.

Edit: More specifically, this refers to adjusting the sensor's calibration. Instead of a value of 0.74V, try setting a slightly lower value, such as 0.72V or 0.70V.

Hello Herbert,

Thank you for your answer.
I will adjust a smaller value in the MSW next weekend (still need to borrow my acquaintance's laptop). I will report on the results here.
An automated scan will also be performed.


Best regards,
TDI driver.

Hello TDI drivers,
The replacement of the sensor improved the voltage reading (0.7V).

Since then, the error has not reappeared.

Thank you, Herbert.

Greetings.

Thank you for your feedback, and safe travels! For further assistance and future support, we recommend checking out the Diesel Mechanics community and considering a complete VCDS diagnostic system.
Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Hello TDI drivers,

ALH, 66 kW, 06/99, 360,000 km, all original. The engine runs great - no hesitation - good power.

I'm still having the problem with the error.
17970 - Quantity setting (N146), upper limit value, intermittent.

It has reappeared and remains unresolved, contrary to my previous statement.
The error occurs very rarely when the engine is warm (after driving about 2 km from a cold start), if it has been turned off for a few minutes and then restarted (or when the ignition is switched on).
No tuning box, everything is original, the MSW has never been moved relative to the pump.
Approximately 2-3 years ago, the MSW was thoroughly cleaned.

The voltage at the MSW sensor is 0.70-0.72V (lower limit) and 4.4V (upper limit) when the motor is off and the ignition is on (0.7xV in measurement block 1, value 3, or both values in measurement block 19, values 1 and 2).
After cleaning, the lower limit was set to 0.74V. By adjusting it to a slightly lower value (0.70-0.72V), the situation improved somewhat (subjectively). I wanted to set it exactly to 0.7V, but I can't go any lower; I'm at the limit.
If I want to adjust the voltage precisely to 0.7V, do I need to adjust the reference ring? And if so, in which direction?
Could this be helpful?

The target values for the upper contact voltage of the ALH are: 4.150 to 4.740 V.
Are these values correct?

"If the error "17970 - Quantity setting (N146) exceeds upper limit, intermittent" occurs, does this mean that when N146 is fully activated via the pulse-width modulated signal, the tolerance range for the end-stop of 4.150..4.740V is not being reached? Which limit (lower or upper) is not being met? (Is this information available, or not?)".

The encoder value G149 is calculated by taking the ratio of two inductances (the reference ring and the inductance corresponding to the encoder position): L1 / L2.
Or is the formula for it more complicated?
What frequency is used for inductance measurement?

This weekend, I will measure all the cables and check for any short circuits or excessive resistance.

Are there any other suggestions?

THANK YOU for your help.

Greetings.
TDI drivers.

You can find something here.
https://de.wikipedia.org/wiki/Halb-Differenzial-Kurzschlussringgeber

I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

It's best to start by checking the connectors and wiring from the MSG (Main System Generator) to the sensor. If you already have 0.7V at the limit, that is not normal.

For your information:

Quote:

For further and future assistance, we recommend the Diesel Mechanic community and a complete VCDS diagnostic system.

hg
Herbert.

Hello TDI drivers,
I was now able to narrow down the source of the error.
Upon powering on the engine control unit, the sensor in the mass airflow meter is tested. The entire range is traversed, and the end values are checked. This happens before the engine is started.
Die Toleranzwerte der Anschlagswerte sind (lt. Sure, here is the translation of the text from German to English:

"Requirements:"
The upper limit:
- below 0.500..0.970V
- Top: 4,150 - 4,740 V
Here's the behavior I'm observing:
When the diesel engine temperature is approximately 25°C (reading from block 7, value 1), the upper limit threshold increases to about 4.280V (read from block 19, value 2), which is normal.
When the diesel temperature reaches approximately 35°C (or even higher), the upper limit of the lower tolerance value drops to around 4.220V or even slightly lower (e.g., 4.180V). These values should also be acceptable, but in some cases, especially when it's 4.220V, and always with lower values, an error message 17970 appears.
"I don't understand why this is happening, because the values are higher than 4.150V. I think the lower tolerance limit of the upper threshold isn't 4.150V, but rather 4.220V."
I tested this with the quantity setting device open. I "softened" the upper limit by using cable ties. It is 100% reproducible; the error never occurs for values above 4.220V, but it always occurs for values below 4.220V.
To achieve a higher value at the upper limit, I have increased the lower value from 0.70V to 0.76V. This will also result in higher values being reached at the upper limit.
So far, the measure has been 100% positive.
The questions that remain are:
- why is the upper limit temperature-dependent?
- What causes such significant temperature fluctuations within the fuel injection pump (metering unit)?

Sure, here is the translation of the text from German to English:

"VG" translates to "Very Good" in English.
TDI drivers.

Hi,

Quote:

why is the upper limit temperature-dependent

I'm more inclined to believe that dirt and sawdust are causing this effect.

There is a technical article about disassembling the interlocking system.

Best regards, Rainer.

and contact resistances (at "cold" solder joints). The temperature dependence should ideally be compensated for by differential measurement.
hg
Herbert.

Hello TDI enthusiasts!

"The comment regarding cleaning is completely correct. However, about 3 years ago (at 60,000 km), I meticulously cleaned the fuel metering unit and found some metal debris in a very fine powder form. Unfortunately, I have no idea whether this dust could affect the adjustment, but I doubt it. Now, I wanted to avoid cleaning it again because it's quite time-consuming. I assembled the fuel metering unit very carefully back then, and the rotor definitely isn't rubbing."

I made a mistake above; the target values, according to the information available online, are:
- below 0.500..0.970V
- The reading is 4,150 to 4,740V, but the actual lower limit is 4,220V; it's above that!!!

I have taken more measurements.
When the vehicle is in motion, the temperature inside the fuel injection pump and/or the mass airflow sensor (MSW) (with current outside temperatures ranging from -2°C to approximately 8°C) is about 20-25°C. The MSW is cooled by diesel fuel from the tank.
If the vehicle is properly warmed up and then TURNED OFF, the temperature inside the MSW (Multi-Screen System) will rise to 35-40°C after approximately 45-60 minutes.
If the vehicle is started, the upper limit in the MSW (MWB 19, measurement value 2) will be 4.20 V or slightly lower.
This means the value of the upper limit is below the threshold of 4.22V, and therefore error code 17970 is generated. So: The car is warmed up, then left idle for approximately 45-60 minutes, started again, and then error code 17970 appears (the times may vary slightly).

Here's the translation:

Now, to my question: Why does the "upper limit" voltage value change with increasing temperature in the MSW (Multi-Stage Water Heater)?
The measurement error is approximately 4.40 (MSW at about 25°C) - 4.20V / 0.044V = 4% -> which is quite significant.
I don't really have a good idea about this.
Could it be that there's still air trapped in the MSW (Multi-Sensor Wheel), and that this air expands when heated, covering only a portion of the half-differential short-circuit ring sensor? This could mean that the two arms are at different temperatures, which would definitely cause measurement errors.
During the last filling of the main storage tank (MSW), air may have entered, and I didn't manually remove any diesel fuel, so there might still be some air in the MSW.
Does the air in the air gap of the short-circuit ring cause a measurement error? (However, since diesel has a relative permeability (µr) value that is almost identical to that of air, I don't think the air in the air gap is a problem, right?)

Since I resoldered the contacts during the last cleaning of the MSW, could it be a contact voltage between two different metals in the solder joints? These contact voltages are usually VERY small, right? I can almost completely rule out cold solder joints; the solder joints were carefully and meticulously soldered.

Or does anyone have any other ideas on this?
Has anyone observed a change in the upper limit value of MSW (MWB 7, Value 1) when the temperature increases, after the ignition is turned on (MWB 19, Value 2)?

THANK YOU in advance.
TDI drivers.

Quote:

The measurement error is approximately 4.40 (MSW at about 25°C) - 4.20V / 0.044V = 4% -> which is quite significant.

no.
I can't tell from a distance whether there is something wrong with your setup.
As a trial, I would adjust the control slider so that the upper value is above the threshold for triggering complaints.
The fuel temperatures change during operation, which is normal.
hg
Herbert.

Hello Herbert,

Thank you for the response.
Yes, I also think that a change in fuel temperature is completely normal.

But why does the "upper limit" voltage value change with increasing temperature in the MSW? The differential sensor was implemented precisely to compensate for changes in inductance due to temperature variations (by performing a "reference measurement" of a known value and comparing it to the actual measured value).

With an approximate measurement error of 4%, it's impossible to talk about any kind of compensation. This isn't a measuring instrument; it's more like a "guess-ometer" (referring to length measurements: with a meter, the measurement error would be 4 cm!).

The question I have is whether this error is normal.
Wenn nein (wovon ich ausgehe) was könnte die Ursache dafür sein? ZSure, here is the translation of the text from German to English:

"Please provide only the translation, without any explanations."
- Transition resistances in the measurement system (e.g., connection of the measuring coils; however, according to my measurements, all resistances are within the normal range).
- Air gap at the differential sensor or shorting ring = air gap/diesel gap in the inductance is changing, or the two arms have different temperatures due to the air (I'm not entirely convinced about this explanation either).
- mechanical tolerances (e.g., the copper short-circuit ring may no longer be precisely positioned; I couldn't feel any tolerances during a test, so I don't think it's likely, but copper is extremely sensitive to temperature and expands significantly).
- anything else? (e.g., metal shavings - I don't think so either, as they probably wouldn't affect the position at the top stop).

Right now, I don't have a really good idea, and I would appreciate any suggestions or counterarguments to my points.
I would be interested in hearing about the experiences of other MSW owners.

Best regards and thank you in advance.
TDI enthusiasts/fans.