Defective Control Unit: Troubleshooting & Repair

hello,
I was just driving home by car, and the jerking started again. I initially thought it might be the MSW (multi-spark ignition), which I cleaned about 1500 km ago. I disconnected the speed sensor connector from the transmission, but it was still the same. Back home, I used VAG-COM to read the error memory, and it shows: 65535 - control unit defective.
Could it be relay 109? Or, as I also suspected, when I cleaned the MSW, I had to resolder the pins, and perhaps one of them came loose, which could be causing the error?

I'm feeling clueless again, just like Rudi.

"Thank you."

Sure, here's the translation:

"Hello"

martin

Ps: 1 owner, 145,000 km.

Evening.
"Also, something else I've noticed when I'm testing the needle valve lifter (it's knocking at 3000 RPM) is that the engine actually starts to jump or stutter. I even tapped it several times with the handle of a hammer. So, it could still be the needle valve lifter. But now I also have air bubbles in the hose between the carburetor and the electric fuel pump, which is making me a bit suspicious because air bubbles and a needle valve lifter... it's all a bit confusing."

What should I do first? The VAG-COM tool isn't showing any error codes anymore, unlike this afternoon when it indicated a control unit failure.

what do you mean when you say "was meint ihr wenn ich"
1. I'm installing a new type 109 relay; it doesn't cost much, only about 10 euros.
2. I'm installing a new diesel filter.

Should I go to a VW dealership and have them test the fuel injector?
"If so, what is the cost of a new injector nozzle from them? I've only got 145,000 km on the odometer, and I didn't really want to replace all four injectors yet."

There's a great technical article about replacing the injectors, but I don't have much time for that right now. What would it cost approximately at a VW dealership?


"Thank you."

already

martin

Hi,

I've also had this error, "control unit defective," twice before. After restarting, it always went away. Now it hasn't appeared for years.
You should replace the needle lifter.

Hello,

The error code 65535, as far as I know, relates to internal issues within the SG system, such as:

Atmospheric pressure sensor, short circuit to ground/BAT.
Reference voltage monitoring.
Voltage monitoring of the stabilizer.
Processor monitoring failure.
etc.

The errors are specific to the SG system.

Regards,
Klaus.

hello,
The error appeared and disappeared in the same way.

Sure, here's the translation:

"Hello"

martin

If you set the settings on the data cable to very high values, you increase the likelihood of communication errors (it's just a single-wire interface). Eventually, you may also receive an error message from VAGCOM if the software can't handle it.

I also read somewhere that fuel injectors are "wear parts" and should be replaced every 100,000-120,000 kilometers because the spray pattern, etc., can supposedly change.

It's not just a rumor that fuel injectors are wear items. It's certainly stressful when 2,400 liters are forced through them at pressures of several hundred bar over 160,000 km. Especially in the center of the "hellfire" (referring to the combustion chamber).