Engine Failure AFN 81kW: Causes & Solutions

Hi,

Now it's my turn, the TDI is causing problems .
He's experiencing engine cut-outs. The engine likely goes into a limp mode for brief moments, because the charging control light illuminates simultaneously and the turbo pressure drops. This whole process lasts less than a second, and I can't identify any correlation with specific load conditions or engine speeds. It suddenly cuts out, at random times, completely unexpectedly. Sometimes nothing happens for 5 km, and other times there are 10 cut-outs within 500 meters.
The error code in the diagnostic memory says "Glow Plug J52 - connecting to ground - intermittent." J52 is the glow plug relay, and it probably doesn't have anything to do with it. I still swapped it out just to be sure, but it didn't change anything .
I'm now suspecting the needle lifter. What's the best way to test it?
I've read about the method of hammering it in, but I haven't tried it yet. Is it reliable? Is it absolutely necessary to maintain exactly 3000 rpm? I can adjust the throttle in the engine compartment, but of course, I don't have a tachometer there.
If you unplug the connector from the NHG (presumably a piece of equipment), the jerking or shaking should theoretically stop. Is this method practical?

Engine: AFN, 81 kW, manufactured in December 1987.
Vehicle: VW Bus T3.
Engine mileage: approximately 110,000 km.

Regards,
Jens.

Hello Jens,

That sounds like a faulty relay 109. With the NHG (presumably a specific system or device), the charging control wouldn't come on at the same time!
It doesn't cost a fortune, I would just try swapping them.

Best regards,
Albrecht.

It doesn't cost a fortune, I would just try swapping them.


Or just accidentally drop the soldering iron.

Best, Andy.

Hi everyone,

Relay 109 does not have mine.
The engine comes from a Passat model year 1998, and those have a relay number 219, which apparently performs similar functions to 109. Unfortunately, it's already new, and it didn't solve the problem .

Regards,
Jens.

Jens 16syncro wrote:

He has engine cut-outs. The engine is probably going into a temporary emergency mode because at the same time, the charging control light illuminates and the turbo pressure drops.

Hi Jens,

If I try to find a possible common cause for these symptoms, the "terminal 15 intermittently without voltage" explanation comes to mind – as if someone is briefly turning the ignition key.
Because the charging control system usually has nothing to do with the Electronic Differential Control (EDC), except that both are connected to pin 15.

In this area, I would start by looking for loose connections or other issues.

Quote:

If I try to find a possible common cause for these symptoms, the "terminal 15 intermittently without voltage" explanation comes to mind – as if someone is briefly turning the ignition key. Because the charging control system usually has nothing to do with the Electronic Differential Control (EDC), except that both are connected to pin 15.

Hi Ulf,

Your suggestion seems correct to me.
Sure, here's the translation:

"Please provide the text you would like me to translate from German to English."
I've just been driving around for a while with VAGCOM connected.
Initially, I had the following errors in memory:

1266 Glow Plug Relay J52
Open or short to ground.
intermittently

626 Glow Plug Indicator K29
Open or short to ground.
intermittently

527 Intake air temperature sensor G42.
Open or short to B+.
intermittently

The first two errors seem insignificant to me. I need to take a closer look at error 3, but with the knowledge from the following hint, it's probably not a major issue either.

I cleared the error codes and started driving. During the journey, I experienced the described intermittent issues several times. VAGCOM showed the following behavior:
- no error message!
- In every instance of failure, VAGCOM also lost the connection to the control unit!

The last clue aligns with Ulf's assumption.

Hey, that's going to be a fun search.
Does anyone have a suggestion on the best way to approach this problem? Measuring it doesn't help, because the interruption only occurs for fractions of a second at undefined times.

Regards,
Jens.

Hi,
A possible solution is to connect a 12V bulb (or alternatively, an LED with a resistor) to terminals 15 and 31, then turn on the ignition and carefully wiggle the connectors and wiring harnesses. If the bulb goes out, the fault has been found or narrowed down.
Personally, I would suspect the ignition switch as the source of the problem.

Best, Andy.

Hi,

I would take an old pair of headphones and connect them to the power supply of the MSG using a large resistor (to prevent it from being too loud) and a long enough cable, and then wiggle it around.

Then you don't have to constantly look at the display, and also, you hear the shortest interruptions as crackling sounds – you might not even see them visually.

Best regards,

Jan.

P.S.: Don't use with high-quality headphones/speakers... they might not like direct current very much, and don't push too much current through them.

Hi,
I can only agree with the previous speakers; it looks like a temporary drop in the on-board voltage. The switching contacts in the ignition switch are always suspect in VWs. Otherwise, of course, it could also be loose battery terminals, defective carbon brushes on the alternator regulator, or a loose connector somewhere in the central electrical system, loose ground straps, and cable connections on the starter motor or alternator, etc.

Good luck.

Olli.

Jan6K wrote:

I would take an old pair of headphones and connect them to the power supply of the MSG via a properly large resistor (to prevent it from being too loud) and then wiggle them around. P.S.: Don't use with good headphones/speakers... they might not like DC current very much, and don't send too much current through them.

Hi Jan,

Good idea . To address the DC problems, I would simply add an electrolytic capacitor in the circuit.
A capacitance in the range of 10-100 µF should be sufficient to prevent the worst of the noise from reaching the headphones, while still allowing the interference to be clearly audible.

Hi Jan and Ulf,

Thank you for the tips regarding the headphones. Since I only have some basic knowledge of car electronics (specifically, direct current ), I'm still not entirely clear on the matter.
Okay, so I'm going to use an old speaker (I have one lying around, I don't have headphones)...
... connect a power cable to terminal 15 and another cable to ground?
... I'm connecting a resistor (how many ohms?) to terminal 15.
... in addition to that, a capacitor connected in parallel (or in series?) with the resistor? (as you can see, I have no idea).

When the electricity is flowing normally, I hear nothing, but when there's a switching event (the power cuts out or comes back on), I hear a crackling sound?

Alternative method:
"Then I thought about simply taking a reliable 12V supply from terminal 30 and connecting it to terminal 15 in the appropriate places, and then driving. I'll start directly at the control unit and gradually move further away (along the wiring harness/contact points). With each step, I'll drive (perhaps combining it with necessary trips, since I don't want to just drive around aimlessly) and see if it still has any glitches. If yes, the problem lies in the wiring harness leading to the control unit. If no, the problem is "further away." This way, I can gradually eliminate large sections of the wiring harness. The problem must always be located between the last contact point that was tested negatively and the one that is currently being tested positively."
What do you think about it?

Regards,
Jens.

Hello,

@Jens
'All those are great ideas, and of course, they're feasible. But do you really want to go through all that trouble before even checking the ignition switch and other connections?'
Considering that even some average drivers are now aware that the ignition switch in VW cars is prone to contact problems.
That sounds a bit like the story of the sparrows and the cannons to me.

Best, Andy.

Hi Jens,

Your method works too, but instead of wiggling the cables, it requires many trips.

It should also work with a speaker; simply connect a resistor, capacitor, and speaker in series, and the order doesn't really matter (just pay attention to the polarity of the electrolytic capacitor).

The required resistance depends heavily on your speaker. I would start with something large (1 kilohm or so), test it (simply disconnect and reconnect the circuit and listen), and then adjust it until disconnecting and reconnecting produces a loud enough crackle.

Of course, this only works when the engine is off, because it requires a perfectly smooth DC voltage.

Best regards,

Jan.

Hello,

For a speaker, using a 220 Ohm resistor in series (make sure it's at least 1 Watt) is a good option. Alternatively, as an auto electrician, you likely have a 1-2 Watt light bulb that you can put in series with the speaker. Another good idea is to use an electrolytic capacitor, 4.7 to 10uF, in series. This eliminates the need for a resistor.

Best regards,
Christian.

If I look at your avatar, I suspect that you might have water inside some connector or cable.
Just a guess .

Hello Jens,

The charging indicator light has its own separate wire running to the front. When it illuminates, it means that the instrument cluster is disconnected from the Kl15 power source. The light then receives power in reverse and grounds through the other instruments. This should also be noticeable, for example, by a slight twitch of the tachometer.
However, the instrument cluster is directly powered by the ignition switch, so the fault must be located there.

Hello.
Wolfgang.