Golf III TDI AHU: Common Problems & Fixes

Hello
I'm new here and I'm having a problem with my car. It won't start, and the fuel pump isn't pumping diesel. I've already searched almost the entire forum, but I haven't found anything that matches my problem.
Das Auto steht jetzt schon fast ein Jahr aus Zeitgründen , zuvor totaler Leistungsabfall , schlechtes anspringen , starker auspuffkwalm . Und dann ging garnichts mehr wollte nicht mehr anspringen , Werkstatt meinte Zylinderkopfdichtung habe ich gewechselt Kopf und Motorblock überprüfen lassen ohne befund zusammen geschrubt und lief wieder . Eingefahren alles i.O. . Nach ca 1500 km gings von Neuem Los, zum schluß bei der Fahrt fehlzündungen wodurch der Zahnriemen gespungen ist und mir die Ventile verbog. Zylinderkopf Instandgestezt lassen und Überprüft , Kolben sind laut Werkstatt in Ordnung . Alles wieder zusammen gebaut und tut sich nichts . Habe jetzt den Fehlerspeicherausgelesen und benötige hife . Golf III TDI Motorkennb. AHU 66 kW, year of manufacture 1997.

VAG-COM
Control unit part number: 028 906 021 BF.
Component or version: 1.9L R4 EDC 00SG 0804
Software Coding: 00002
Workshop Code: WSC 00028

9 errors found:
00522 - Coolant temperature sensor (G62)
30-10 - Interruption / Short circuit after positive voltage - Interrupted.
00550 - Injection start control.
17-10 - Interrupted.
00553 - Air mass sensor.
31-10 - - Interrupted.
00513 - Engine speed sensor (G28)
03-00 - No signal.
01268 - Quantity adjuster - N146.
18-10 - - Interrupted.
00765 - Feed mechanism for sliding gate.
35-10 - - Interrupted.
00542 - Needle feed mechanism.
30-10 - Interruption / Short circuit after positive voltage - Interrupted.
00539 - Sender for fuel temperature.
30-10 - Please purchase a full version. - Interrupted.
01237 - Fuel shut-off valve.
31-10 - - Interrupted.

Brake control unit / Brake electronics control unit.
Airbag control unit.
Steering wheel immobilizer.

Sure, here's the translation:

"No mistakes."

"The coolant temperature sensor was previously defective, but it didn't cause any issues because it was still working. The mass airflow sensor was disconnected for the test start, which is why the error code appeared."
I think all of this is a consequence of something else, and I've already checked all the cables and connections.
I hope someone in this forum, from the diesel specialists, can help me or give me some tips. Thank you in advance.

Mugel1983 wrote:

... It won't start, or the fuel pump isn't pumping diesel. ... 00550 - Injection start control. 17-10 - Interrupted. 01268 - Quantity adjuster - N146. 18-10 - - Interrupted. 00765 - Feed mechanism for sliding gate. 35-10 - - Interrupted. 00539 - Sender for fuel temperature. 30-10 - - Interrupted. 01237 - Fuel shut-off valve. 31-10 - - Interrupted.

What do you notice about these errors that have been copied above?
Is there not at least one connector missing?
These are all signals that are transmitted via the multi-pin (8 or 10 pin, depending on the configuration) connector on the VP37.

Quote:

... 00522 - Coolant temperature sensor (G62) 30-10 - Interruption / Short circuit after positive voltage - Interrupted. 00513 - Engine speed sensor (G28) 03-00 - No signal. 00542 - Needle feed mechanism. 30-10 - Interruption / Short circuit after positive voltage - Interrupted.

These errors suggest a missing ground wire or a severed engine wiring harness.

It appears that all the errors have the same root cause (e.g., missing engine mass, cables not properly connected to the MSG...).

Find and remove cable ties.

Thank you.
Okay, the main cable harness is complete and free of corrosion. The wiring harness is also all connected. The only thing I'm unsure about is the round connector with 8 or 10 pins. Is that a connector, or is it a fixed part? I've never known whether it can be disconnected.

Mugel1983 wrote:

"So, these mass-produced cables are completely free of corrosion."

What is the resistance between the engine block and the negative terminal of the battery?
What is the electrical resistance between the engine block and the car body?

Quote:

The wiring harness is also completely assembled.

The error log clearly indicates something different.

Quote:

The only one with 8/10 poles ??? Is this a connector, or is it a whole unit because I've never known if it can be replaced !!

Is this it?

If this component is missing or defective, the pump will not receive any signals. This is indicated by the first category of errors I mentioned.

There has to be more to it than that.

Thank you .
I will get to work and go through your points, and I will thoroughly check everything again and also take measurements. I am glad to be registered here and to receive help from experts, and I will get back to you with the results.
Greetings and a happy New Year .

Which errors are rewritten after the error memory is cleared?

The problem might also be caused by a loose crankshaft pulley.

Okay, I've been diligently measuring things now.
1.
What is the resistance from the motor block to the negative terminal of the battery? 0.3 Ohms.
What is the resistance between the engine block and the car body? It varies between 0.5 and 0.3 Ohms.

I don't know what that means, but I hope the question is answered and you can say something about what it is supposed to mean.

"I checked all the connectors to the diesel pump and other sensors, and in all cases, the battery voltage of 12.85 volts was present. The fuel shut-off valve clicks, the glow plug system works, and the sensor for needle lift also has battery voltage. However, the semi-circular connector from the diesel pump (specifically, the part that includes the fuel temperature sensor, fuel quantity adjuster, and control slide sensor) is showing different readings. This is the part on the side where 7 wires connect to a semi-circular connector. Unfortunately, I don't know the exact designation. On 2 of the wires, there's battery voltage, on 1 wire, there's no voltage, and the remaining 3-5 wires have approximately 3-5 volts. I'm not sure if that's supposed to be the case?"
In my opinion, the rest is fine; everything is properly connected where it should be.
The only thing I've noticed is that when I measure from the positive terminal of the battery to the engine block (where the ground cable is attached), I get about 2 volts difference. I think this might indicate a grounding problem, but I'm not sure if that's my problem.
I didn't have time to go into more detail, but I'll test it next week. I work from 9 am to 6 pm during the week, and the car is parked outside, so it's already dark. I'll take everything apart again, clean it, and take measurements, and then try it out.
P.S.: I haven't cleared the error codes yet, but I will check again after I've reviewed everything. I'll get back to you next week.
I welcome any tips or other assistance, and I would be very happy to receive them. Best regards!

haamerschlosser wrote:

Which errors are rewritten after the error memory is cleared? The problem might also be caused by a loose crankshaft pulley.

It's not due to that; everything is tight. The engine is revving fully, and I've also checked the compression (28 bar). We've verified the valve timing using a timing tool and a feeler gauge, and everything is correct. When I first disassembled it, I replaced the timing belt and the tensioner pulley.

Mugel1983 wrote:

So, I've been diligently measuring things now. 1. What is the resistance from the motor block to the negative terminal of the battery? 0.3 Ohms. What is the resistance between the engine block and the car body? It varies between 0.5 and 0.3 Ohms.

That sounds a bit pretentious.

Quote:

... The only thing I've noticed is that when I measure from the positive terminal of the battery to the engine block (where the ground cable is attached), I get about 2 volts difference. I think this might indicate a grounding problem, but I'm not sure if that's my problem. ...

"Like a 2-volt difference?"
If you use the engine block as a ground when taking measurements, the measured voltage will be approximately 2 volts lower. If this is the case, you have a grounding problem.

Quote:

... Fuel shut-off valve clicking...

It actually sounds good.


But again.
Please correct all errors and then check again to see which errors reappear immediately.