AVF TDI im Passat startet kalt manchmal seltsam!? | Posts 64+

Hello Klaus!
Yes, unfortunately!
I haven't checked anything yet. I simply put in a different battery and tried -> the error is still there. Then yesterday, I installed a new G28 -> today, the error appeared twice in quick succession. I can't shake the feeling that a temperature sensor is causing the problem, but I can't say why. The G81 was in the memory a long time ago, but with no consequences! I still replaced it back then. Today, it's not in the memory. Could a temperature sensor occasionally be in an unfavorable range WITHOUT displaying an error in the memory? For example, the intake manifold pressure/temperature sensor? I also suspect that one, because it's a bit oily and might not always measure correctly .

Greetings.

Okay, then please describe the error again.

Sorry for the late reply, I've been a bit stressed with the move. I'm just getting home.

Regarding the error: I thought this was already a known issue, so I'm just stating that it has occurred again. The problem is that the starter motor turns, the engine makes a combustion sound (during starting), but it doesn't start. It happened again just now. However, the duration of the error is currently very short, about 2 seconds. That's why the G28 sensor isn't being triggered. If the error lasts longer than approximately 5 seconds during starting, then the G28 sensor will trigger with an implausible signal. When it actually runs, it works perfectly and without any problems.

Greetings.

Quote:

Regarding the error: I thought it was already clear a long time ago,

We thought so too. You mean the symptoms.

Hm,

Why does the error G28 appear? Is it due to undervoltage in the control unit? Or is it because the starter motor is not turning the engine properly, or is there still something wrong with the electrical circuit of the G28?

Unfortunately, we still don't have any definitive information about whether the starter motor is simply weak, or whether there are setbacks (due to premature or misfiring) during the starting process. That's why this makes the case difficult, because depending on the error, you have to investigate in two different directions.

To rule out the starter motor as a possible cause, I ordered a new one from Yabazzo. Okay, but please take it easy now.

What if he's not What could that be in terms of setbacks?

Greetings.

Quote:

What could that be regarding setbacks?

It has been mentioned before.

Is he going to retaliate, or will he just (weakly) stand by and do nothing?

You should investigate this, if necessary by consulting a specialist.

Mike3BG wrote:

So, in order to be able to rule out the starter motor as well, I ordered one from Yabazzo. Now, you're going to start running out of money

.

"Well, if I didn't already have one, I would have bought a clamp-on ammeter with memory for that. Then, after testing, I could have said for sure whether it was the starter motor or not!"
But there's a silver lining: maybe you'll notice a damaged cable while you're replacing the starter motor. (Sender/Starter motor)
I didn't mention buying a starter motor (even though I...), because nobody seems to have a properly tested one for it.
derteileklaus

Hello!

I'm back home. Now, it happens at least 2 times a day. Now I'm driving home again. It's only for a very short time, but it's noticeable. The starter motor doesn't stop! It spins "normally," but it really sounds like there are "backfires." Sometimes it's very brief, sometimes it lasts longer. So far, it's happened twice for a longer duration, and then the G28 error code appeared in the memory. I have a feeling it takes about 5 seconds of repeated attempts (with setbacks) for the G28 to write the implausible signal to memory.
Did I miss something? I've asked about the misfires and backfires a few times, but I still don't know what you suspect is causing them.

By the way: The connections/cables on the starter motor are completely free of oxidation and in perfect condition! That's even something the workshop took care of for EUR 200,- .

I can't shake the feeling that the problem has been occurring more frequently since the battery was replaced. The battery I have in now is the one I had before, so it's a bit weaker than the new one, of course. Could that be related, and could it, in combination with a possibly faulty starter, be causing the problem to occur more often? Or is it just coincidence again ?

Greetings.

Hello!
New findings, unfortunately, not yet good ones. Okay, let me quickly summarize:
Battery changed.
Replaced the G28 (engine speed sensor).
Replaced intake manifold pressure/temperature sensor.
Replaced the ignition switch.

The starter motor is still at home, and so is the G82 (fuel temperature sensor). I haven't had time to install them yet, as it's a bit time-consuming. I'll probably be able to do that on the weekend, when I have to replace the rear brakes.

So far, no success . Even with the currently higher temperatures, the error occurs, although very rarely.
I can't seem to shake the thought that it's happening because of the starter shock. Most of the time, it starts normally, but when it starts in a strange way, I have the feeling that the vibration somehow triggers it. This also explains why the error sometimes only occurs for a very short time, and sometimes lasts up to 8 seconds, hesitating and struggling. The higher the outside temperature, the lower the threshold for the problem to occur. Sometimes it's so short that it's barely noticeable, but in the winter, for example, it has been as long as about 8 seconds.

The starter motor will be replaced, and the G82 module as well, but after that, things are starting to get complicated. Then there's the mass airflow sensor (MAF) and the G62 coolant temperature sensor, and the crankshaft position sensor. The question is: could the sensors actually be the problem, considering the engine otherwise runs perfectly? "When starting (and ONLY when cold!!!), no plausible values are displayed, but suddenly it becomes functional due to the starter's vibration?"

One more thing: I once had a consultation with someone else and I told him everything that was new and had already been replaced. He said that it could also be a mechanical problem with the fuel line . Specifically, he mentioned a check valve that might not be 100% tight in cold conditions, which could prevent the tandem pump from building up full pressure immediately . Does anyone know what that's supposed to mean?

Regarding the relay suspects: Can we assume that if the starter motor turns in the event of a fault, the usual suspect relays are okay? Or should I also start my troubleshooting there? He definitely never stalled once he got running.

I would be very grateful for any further tips.

Greetings.

EDIT: I found the part. It's probably the VALVE at the top of the diesel filter, the one with the two O-rings. I also ordered that, and I'll try installing it this weekend.

EDIT2:
I've reviewed the original thread again, and I don't think I described the actual error clearly enough. Because the problem is no longer a starter motor that is rotating too slowly or stopping altogether, but rather the following:
Cold start: Ignition on, the glow plug illuminates briefly. Then, you start the engine, and while the starter motor spins at a seemingly constant and "normal" speed, you can feel and hear that the engine is already firing (I don't know on how many cylinders), but it still doesn't start (the starter motor seems to be working against the engine starting). This behavior can last for a very short time (a fraction of a second) or up to 8 seconds. It's not just normal starter cranking (whirring sound), but it's accompanied by ignition noises and gentle knocking. However, if you "flip a switch," it turns on and then runs perfectly without any problems.
The thread has become quite messy. I would like to verschandeln it up or start a new one and then have this one deleted. Admin, would that be possible?