Do I Need a New Control Unit?

Hello everyone,
I'm brand new to this forum, so I apologize in advance for any mistakes I might make in my questions.

"For some time now, the yellow engine check light has been illuminated on my car, and it's also showing up on the display."
"Exhaust workshop" - The car is going into limp mode.

I have now been to Germany 5 times and 3 times to workshops abroad. Various parts have been replaced, such as the mass airflow sensor (MAF) twice, the J17 relay, the AGR valve, and other components were installed for testing purposes, including a turbocharger and other parts that I don't know specifically.

The control unit was opened and the necessary soldering work was performed. According to the information provided, the entire wiring harness was checked, as well as all connectors and grounding points.

The error is still present. I'm not sure what to do next; one person says it's the MSG (Main System Generator), while another suggests replacing the wiring harness. Returning the item is definitely not an option.

Question 1.
Can I generally determine if the MSG (Main System Gateway) is defective using, for example, shareware VAG Com software and a laptop? Is it possible to restore the device by installing the original software? Can I put the MSG into a "ready-to-sell" state by resetting, formatting, or similar methods? And where can I obtain this software? When searching online, you find thousands of flash tools, but that's not what I want.
To tune up the car.

Question 2.
"Wiring harness is easy to say. Do you get the complete thing, and where do you get it from besides expensive places? And most importantly, who installs it, and at what price? I'm not even sure what questions I should be asking about this, sorry."


VW Golf IV TDI Identnr. WVGZZZ1TZ5W016362
Vehicle system: 038906019KP Control unit: 038906019KP
1.9L R4 EDC 0000SG 4902 Coding 2.
Diesel EDC15P+ Engine type: AXR
WVWZZZ1JZ4W1 79946 WVZ7Z0D9452204

5 errors detected.
1. 17932 P1524 035
Fuel pump relay J17.
Short circuit to ground / Intermittent.
2. 17903 P1495 035

Exhaust gas recirculation (EGR) control valve - N345.
Short circuit to ground / Intermittent.
3. 17849 P1441 035

Exhaust gas recirculation valve.
Short circuit to ground / Intermittent.
4. 19557 P3101 035
Throttle body control motor - V157.
Short circuit to ground / Intermittent.
5. 17957 P1549 035

Magnetic valve for boost pressure control - N75.
Short circuit to ground / Intermittent.

Thank you for listening to me.

Hi,

1)

Quote:

Can I restore the device by installing the original software?

If the control unit has been tuned, installing the original software will revert it to its "original" state.
It cannot be done with VAG-COM or VCDS, but requires other tools.
Personally, I think you have a mass problem with the engine/wiring harness. It could also be a partially damaged circuit board in the control unit (ECU), but I haven't encountered that specific case before.
Theoretically, a failed tuning process could also be the cause, but in that case, the error would either appear immediately after installing the software or never occur at all.

Can these errors be cleared with VCDS, and do they reappear after a certain time, or immediately?

If immediately:
-> Install a different EDC15P+ control unit with the same engine code. The car won't start with it (due to the immobilizer), but if you don't get any error messages when you turn on the ignition, you'll know that the problem is at least related to the control unit.

Regarding point 2: No idea.

Best regards, Rainer.

Hello, thank you for the quick reply.

No, I haven't performed any tuning.

The errors cannot be cleared at the moment. After disconnecting the battery and removing the colored connectors near the main system gateway (MSG), they can be cleared. Sometimes they reappear after a few minutes, and sometimes after a few hours.

You mean I should buy an EDC15P+ unit without knowing for sure if it's what I need, or are there other possibilities?

Can you only test each wire individually when troubleshooting a motor or wiring harness, or are there other methods?

Best regards.