G28 Error: Find the Mistake!

Hi!

I've already searched... and found some things. But nothing that answers my question!
Yesterday, my Golf 3 TDI (1Z) failed to start once. Since then, it has been intermittently misfiring with a lot of smoke coming out! It's happening sporadically...

Error according to VAG-COM:
00513 G28 Sensor, motor speed.
No signal, intermittent.

According to the error database: cable break/short circuit.
Another cable broken again!? So, here's my question:
Which cable? From pin 2 to the control unit? And where could the fault be located?
It probably happens more often.

Should I immediately run a new cable from the control unit to the G28, or should I measure first? It could be fine, because it's only happening sporadically }.

How does the G28 work... or why are there ground connections and a cable to the control unit (STG)?
Why not just switch on the mass once, if it's supposed to be switched on?

Thank you for all the answers!

Best regards,
Matthias

TDI_Butze wrote:

Error according to VAG-COM: 00513 G28 Sensor, motor speed. No signal, intermittent. According to the error database: cable break/short circuit. Another cable broken again!? So, here's my question: Which cable? From pin 2 to the control unit? And where could the fault be located? It probably happens more often...

Hi Matthias,

The sender circuit consists of wires 1 (sender ground to the control unit) and 2 (signal line to the control unit).
Cable 3 is the shielding.

Several possibilities could be the cause of the error: a break in cable 1 or 2, corroded or damaged connector contacts, a short circuit between pins 1 and 2 or 1 and 3, or a defect directly within the sensor.

Thank you, Ulf!

Well, if I use a measuring device now, it's probably okay again! Today, he hasn't done it anymore, at least! But definitely, when I go to the IAA on Wednesday .

I'll leave it as is for now and investigate further if it happens more often. Maybe it's related to my previous mistake, like the pump cable having a short circuit to ground?
I'll check it out sometime this week, and if the sensor isn't too expensive, I'll replace it.

Best regards,
Matthias

Hi!

After a few instances of jerking, I read the error memory again today.

This time, it's not fault code 513, but 553, indicating a mass airflow sensor (G70) with an implausible signal, occurring intermittently.
Could the two errors be related?

TDI_Butze wrote:

This time, not 513 but 553 G70 mass airflow sensors, implausible signal, intermittent. Could the two errors be related?

Hi.

AFAIK, probably not.

Unless the oxygen sensor temporarily malfunctions, the engine control unit will count fewer revolutions. However, it will simultaneously receive the signal for normal airflow, which would theoretically result in a calculated air mass per stroke that is a multiple of the normal amount (this is just a theoretical scenario).
But then, the diode replacement for the LMM should also be recorded as an error, which the 1Z system apparently doesn't do yet.

Hello,

as is often the case with intermittent and sporadic errors (and stuttering):

1. Check relay 109.
2. Check ground connections.