High-pressure generator (G65) 009 - Ground interruption/short circuit

Hello,

I'm experiencing several issues with my Touran 1T (1.9 TDI) with the AVQ engine that I'm unable to resolve.
Initially, the turbocharger was not functioning correctly. The underlying cause was a known issue: the engine wiring harness was chafing due to the vibrations. I soldered this, and the turbo started working again (MKL = off).

Besides the various errors, it's also noticeable that the "large" fan runs continuously throughout the entire journey immediately after starting, even when the engine is cold. However, the fan does not run when the ignition is off. As a first step, I replaced the high-pressure valve (G65) of the air conditioning system (FEBI) because a short circuit to ground was indicated. Unfortunately, this didn't change anything. The fans are surprisingly easy to turn, contrary to what the error log indicates.

Does anyone have any ideas about what other underlying causes might be present here? Also, can someone tell me whether the "large" fan is for the air conditioning system or for engine cooling?

I've now received the tip that the coolant temperature sensors G62/G83 are prone to failure and can cause such an anomaly, especially when the fan is running continuously. Alternatively, a broken wire could be the cause.
I didn't notice any broken cables. Now, I'd like to look up the original part numbers. Can anyone tell me if the two sensors (one on the side of the engine block and one on the bottom of the radiator) are the same?

VAG wrote:

I have now received the tip that the coolant temperature sensors G62/G83 are prone to failure and can cause such an anomaly, especially when it comes to a continuously running fan,

Absolutely correct. However, your error log clearly indicates that the air conditioning system is reporting a high-pressure error. Accordingly, your fans are running.

VAG wrote:

Alternatively, a broken cable may be the cause.

Okay, that's correct. But for now, focus on getting rid of the G65 error. It's highly likely (over 90% probability) that this is causing your continuously running fan.

Read the measurement values from the STG 08. What are the suction pressure and back pressure at the compressor when it is turned off? What does each donor report?
If everything seems okay so far, please check in Erwin (siehe Fehlerdatenbank) how G65 is wired. The control unit is reporting a short circuit to ground. It's quite possible that the G65 is missing its power supply (fuse, wiring, etc.) or that something is causing a short circuit in the power supply.

Sure, here's the translation:

"Thank you in advance!"

Okay, I'm now navigating to the "08-Climate/Heating" control panel, then selecting "Settings." "Measurements" and displayed the values that seemed meaningful to me when the system was at a standstill (see Screenshot).
It's strange that I can't find the "G65" sensor listed anywhere. However, I can't find any information about the terms "suction pressure and back pressure at the compressor" either.
To check the refrigerant pressure, I temporarily pressed the valve stem on the filling valve. I only heard a very faint, almost silent hissing sound (it seems to have been just the difference in thermal pressure). In that case, it seems to be completely empty.

Hello,

I was looking for the high-pressure sender located on the injection molding wall in the engine compartment, near where the air conditioning lines enter the passenger compartment.

Best regards, Rainer.

dieselschrauber wrote:

Hello, I was looking for the high-pressure sender located on the injection molding wall in the engine compartment, near where the air conditioning lines enter the passenger compartment. Best regards, Rainer

I've already located and replaced the sensor on the car (it was located on the front right side, towards the direction of travel, near the radiator). I just can't find it in the list within VCDS to read it out in more detail.

VAG wrote:

Regarding the refrigerant pressure for climate control, I temporarily pressed the valve pin on the filler valve, and I only heard a very small, almost silent hissing sound (it seems to have been merely due to the thermal pressure difference). In that regard, it seems that this is already completely empty.

I agree completely. The logged pressure reading of 0.0 bar also suggests that the refrigerant system is empty. However, I can't understand how the high-pressure switch could trigger without any refrigerant. I would recommend taking the system to a specialist in refrigeration technology (not necessarily an automotive repair shop) and having them check it for leaks.

Then it will certainly be necessary to replace a part. Following this, the filter dryer should also be replaced before refilling.

What surprises me is that you've only talked about the fan so far. If the refrigerant is empty, the air conditioning system won't cool anymore. Didn't you notice that before? Or did you perhaps depress the low-pressure valve while the system was running?

I can't say for sure whether the air conditioning system has been malfunctioning for a while, as I can no longer ask the previous owner. However, it is no longer needed.
What's most important to me is that the fan finally stops running and that I have a clear understanding of what's causing all these errors.

Here's what I've done in the meantime:

- Both coolant sensors have been replaced (with no effect).
- Battery charged, reason: Low voltage at terminal 30, error (no impact).
- High-pressure valve (G65) temporarily disconnected for testing (no influence).

What I've also noticed is that the fan (whether the system is warm or cold) always starts a few minutes after the initial startup. In other words, if a short circuit (either in the sensor G65 itself or in the wiring harness) were the cause, wouldn't the fan immediately start running?

If you no longer need the climate control system, you only need to address the G65 error. Please examine the wiring of the G65.
I'll quote myself here:

guste100 wrote:

... then check in Erwin (siehe Fehlerdatenbank) how G65 is wired. The control unit is reporting a short circuit to ground. It is quite possible that the G65 is missing its power supply (fuse, wiring, etc.) or that something is short-circuiting the power supply.

Alternatively, you can search for the pin number in the Erwin (siehe Fehlerdatenbank) system and determine the voltage it switches. If you no longer intend to use it, you can directly bridge the G65 pin at the control unit. It's a bit of a makeshift solution, but if you want it done without air conditioning...

I checked all the wiring using the wiring diagram (see sketch in the attachment). All wires have continuity to their destination (indicated by a beep), and I couldn't detect any short circuits to ground. I measured from both ends of each wire. There is also voltage (approximately 12V) at the sensor, and the fuse is also okay. I also refilled the refrigerant, even though I initially thought I wouldn't need to.

In addition, I noticed that at the exact moment the fan starts, its speed also increases from approximately 850 RPM to 1000 RPM. Perhaps that provides another clue?
- Is it possible to test the high-pressure sensor yourself in any way? I once heard that this item was defective when it was brand new for someone.
- Is there a way to bypass the sensor so that the fan turns off?

Here's the new Fehkerscan...

The new error log is surprising.
There, the high-pressure error continues to be listed as intermittent. (which isn't entirely surprising).
But he also complains about a lack of pressure. But not occasionally, but constantly. And that seems very strange to me. First, this shouldn't happen after the filling process, and second, a high-pressure error cannot occur if there is insufficient pressure.

Take a look at the wiring diagram to see if it includes any other pressure sensors. I don't understand it otherwise.

Can you measure a difference between normal operation and a fault condition on the line between the climate control system (STG) and the high-pressure sensor? I'm not sure if there's just an overpressure/normal pressure on/off signal, or a digital pressure signal, or an analog signal. For a precise analysis, you'd probably need to use an oscilloscope, but maybe a digital multimeter will already provide some indication.


The idle speed is increased in several cases: particulate filter regeneration, a weak battery, a high load on the alternator, for example, due to the high power consumption of the fan at a high setting. If you're interested, take a look at the measurement data blocks; you might even find something there that explains why it's increasing the speed.

guste100 wrote:

The new error log is surprising me. There, the high-pressure error continues to be listed as intermittent. (which isn't entirely surprising). But he also complains about a lack of pressure. But not occasionally, but constantly. And that seems very strange to me. First, this shouldn't happen after the filling process, and second, a high-pressure error cannot occur if there is insufficient pressure. I mean that the "sporadically" part is irrelevant, because the error is always there, even immediately after deleting. He essentially stays. Take a look at the wiring diagram to see if it includes any other pressure sensors. I don't understand it otherwise. I couldn't find it. Can you measure a difference between normal operation and a fault condition on the line between the climate control system (STG) and the high-pressure sensor? Since the error, contrary to the error log, is not sporadic but always present, there should be no two cases (error case/normal case). I'm not sure if there's just a simple on/off signal for overpressure/normal pressure, or a digital pressure signal, or an analog signal. To get a precise analysis, one would probably need to use an oscilloscope, but perhaps the digital multimeter will already provide some indication. I don't have an oscilloscope. I assume it's an analog signal, after all, it's basically a very old Touran, from the first generation (-; The idle speed is increased in several cases: particulate filter regeneration, a weak battery, a high load on the alternator, for example, due to the high power consumption of the fan at a high setting. If you're interested, take a look at the measurement data blocks; you might even find something there that explains why he's increasing the speed.

Fortunately, the car doesn't have a particulate filter yet. However, the engine speed increases briefly just before the fan starts and draws power. It's essentially a precursor to the fan turning on. According to the readings, the battery voltage doesn't actually look that bad. Error scan?
In which measurement blocks can I find specific information? However, I don't find the reported errors to be very plausible. For example, when considering a "stiff/blocked" fan, the issue doesn't seem to be related. He turns easily and runs all the time.

What's also strange is that in some cases, a significantly higher mileage (see below) of 209761 km is displayed (actually, it has 146940 km). The odometer has never been tampered with or anything like that. I just checked a log from March 2024, and at that time, it recorded 106829 km for the mentioned errors. The "lower limit exceeded" error is not sporadic either; it persists after each clearing. Regardless of the fuel level ({= 3/4}).

Address 18: Auxiliary heater
Label file: DRV\1K0-815-071.clb
Part number: 1K0 815 071 G
Component: Auxiliary Heater 020 1312
Revision: A Serial Number: 09010046
Encoding: 0000011
Operating number: WSC 52442 141 51624
VCID: 291A0BA7801234D9B5-807C

4 error codes found:
00664 - Fuel level indicator.
002 - Lower limit exceeded - Intermittent.
Environmental conditions:
Error status: 00100010
Error priority: 0
Error frequency: 4
Lost Count: 197
Mileage: 209,761 km
Time: 0
Date: 2000.00.00
Time: 06:40:25

00003 - Control unit.
014 - Defective - Intermittent.
Environmental conditions:
Error status: 00100010
Error priority: 0
Error frequency: 4
Lost Count: 197
Mileage: 209761 km
Time: 0
Date: 2000.00.00
Time: 06:40:25

01444 - Undervoltage trip (automatic).
000 - - - Sporadic
Environmental conditions:
Error status: 00100010
Error priority: 0
Error frequency: 4
Lost Count: 197
Mileage: 209761 km
Time: 0
Date: 2000.00.00
Time: 06:40:25

01320 - Control unit for Climatronic (J255)
004 - No signal/communication - Sporadically.
Environmental conditions:
Error status: 00100100
Error priority: 0
Error frequency: 1
Lost Count: 87
Mileage: 146,940 km
Time: 0
Date: 2000.00.00
Time: 19:42:02