Passat TDI 1Z also failed | Posts 32+

Hi forum,

First of all, thank you very much for all the helpful and insightful tips here!

I have a Passat TDI '94 (1Z) that is also affected by the issue described here.
suffered from the problems described in various places: the engine fails.
'While driving, the preheating light is constantly on; restart.'
Only possible after some time. The error drove me half crazy.
done.

After I had soldered almost everything that was supposed to be soldered, I...
'Relay '109' (DWA, partially motor-driven) is missing.'
The error ultimately lies there.

Hi,

It's highly likely that DWA was responsible. After driving a slightly longer distance today and not experiencing any other issues, I think the problem has been resolved.



The problem was a relay (which was properly soldered) on the...
DWA board. During test drives with the 'freely hanging DWA' (presumably referring to a parking assistance system), I experienced...
I've noticed that some individual relays are getting extremely hot - hotter than...
Components are typically subjected to temperatures exceeding 60 degrees Celsius. 'Does one...'
Please be careful when manually testing the contacts of this relay; ensure you do so correctly.
identify the described symptoms. (DWA, to the configuration page)
looked, plug facing upwards: from the two smaller relays on the left.
(This was the lower part).

Since I don't really need the DWA anymore, I have the relay.
'Permanently bridged.' 'Test drive': 2 weeks / 1500 km - everything worked perfectly.

Thank you again, and best regards.

Martin.

I also noticed back then that it can get very warm inside. Apparently, this part is not a masterpiece of engineering.

My DWA (device) isn't giving me any more problems, so it was definitely a soldering joint in my case.

A question: Is your preheating indicator now working normally again? My light wasn't working during the power outage, and unfortunately, it's still not working now. (It's not the bulb!) Due to lack of time, I haven't been able to investigate further yet.

My preheating indicator is working again since the repair.
completely normal.

However, I once had a different error in the...
Electricity (sigh), with several warning lights illuminated, including...
The preheating indicator was not working correctly. Back then.
It was a whole bag of cold solder joints right away.
central connector of the dashboard circuit board, where
A thick cable harness without strain relief is pulling and...
shakes. It might be worth taking a look.

I hope you had a merry Christmas...

Martin.

Hello everyone.
(I have a Passat, model 1Z, manufactured in 1994.)

The problem sounds familiar, and I still don't have a definitive answer. I've tried to analyze the error further. Perhaps this will be helpful, and/or maybe someone can help me further.

My history.
The engine shuts off, and the glow plug warning light illuminates at the same time. The engine can be running at a high or low RPM. The issue seems to occur more frequently after a certain amount of driving time, but this is not always the case. I also sometimes feel that it might have something to do with driving on curves. (Do you drive more curves or straight roads ??? )

- The error disappears after a certain amount of time, with or without the ignition being turned on (initially).
- I once had a diagnostic device from a dealer, but I couldn't read any error codes when there was a problem.
- I speculated on Relais 109 and made some trades, but it didn't yield any results.
- I have added control diodes for the control voltage and general power supply to the old relay.
- - Symptom: In case of engine failure, the general power supply is active, but the control voltage is lost.

The workshop said it was the control unit, so it was replaced. Unfortunately, the same error occurred. Luckily, I was able to return the part. However, the workshop noticed that the error appeared or disappeared when moving the cables in the dashboard. They said it shouldn't be fixable or would be too complicated and therefore too expensive. 'The wiring diagram is so difficult, constant flipping through pages... blah blah...' At that time, I was unfortunately traveling, and my wife had to deal with them. (I have the feeling that they probably want to sell me a new one, even though the current one is otherwise still in good condition.)

- The car wouldn't start at all and was left in the garage.
- I then added a switch to bypass the 109 component (on the working contact side). I had read somewhere about bridges and had once tried fishing there.

- - Result: When the switch is activated, the constant indicator light goes out, and the engine can be started.
- The tax voltage then reappears, either immediately or with a delay. However, with a cold engine, the motor stops, even though the 109 is bridged with the switch. Therefore, the MSG must be shutting down the motor through another means, and there cannot be any loose connections in the wiring leading to the 109. This indicates a fault somewhere in the circuit leading to the MSG. When the engine is warm, there's a slight jerk when it reaches 109 km/h, but due to the engine's inertia, it usually continues running.

So, you can drive using the switch. If the control signal is lost, the switch will flip, and the system will continue operating, provided that the vehicle is moving at a certain minimum speed when the error occurs. Once the signal for '109' returns, you can disengage the switch. You can leave it running continuously, but you must remember to turn it off when you park, otherwise the battery will be drained.

If you're not getting a signal for the '109' display, a firm tap on the dashboard in the right-hand area of the instruments often helps to restore the signal.

My error has recently progressed; now, the engine sometimes stops even with the switch on, but the glow plug indicator then flashes. Only when the flashing stops can the engine be restarted - my switch doesn't help at all in this situation. Tapping the dashboard can sometimes help fix the problem.

As far as my report and my pathetic attempts go.

Who is familiar with the logic of MSG?
Questions:
- What signals must be present before the MSG in order for 109 to be activated? If channel 109 is not activated, it appears that the MSG indicates this by continuously illuminating the preheating indicator.

- Which of these signals causes the MSG (presumably a system or device) to shut down the engine or reduce its power to the point where it stops, when the signal reappears?

- What missing or incorrectly received signal causes the MSG (Motor Control System) to make the glow plug indicator blink, even when 109 is activated (simulated by my switch), and simultaneously causes the MSG to stop the engine (how), even though it has been prevented from accessing the engine via 109 because 109 is bridged?

- Is there something like an emergency stop? If so, what are the triggering causes?

- Which of the potential signals are related to the dashboard area?

- I read about it in a book with wiring diagrams (unfortunately, for a 95 model). Could it be related to the circuit board for the oil pressure sensors in the area of the tachometer?

Sorry for the long essay. I couldn't write it any shorter or with more detail.

Thank you in advance for any suggestions.
Ulrich Veith.

Ulrich Veith wrote:

What signals must be present before the MSG in order for 109 to be activated?

Starting from the '97 AFN model, the MSG only requires a positive connection from the ignition switch (terminal 15) to pin 38. Then the MSG activates the 109.

Quote:

If 109 is not switched through, it appears that this is indicated by the MSG with a constant illumination of the preheating indicator.

I can't understand that from my recollection of the AFN.

Just one more fact about the AFN: after a stall, the MSG (presumably a sensor or module) went offline, preventing ignition and making it impossible to start the engine.
I installed a starter button, among other things, and over the years I've come across this issue a few times.

To what extent is this applicable to a 1994 1Z model, or...? Unfortunately, I don't know how to help you.

Hi,

Quote:

Just one more fact about the AFN: after a stall, the MSG (presumably a system or component) was without ignition and unable to start the engine, despite attempts to do so.

Isn't that just the standard anti-theft system that prevents the starter from being engaged while the engine is running?

Best regards,

Jan.

Jan6K wrote:

Quote: Just one more fact about the AFN: after a stall, the MSG (presumably a system or component) was without ignition and unable to start the engine, despite attempts to do so. Isn't that the standard anti-theft starter interlock, which is designed to prevent the starter from being engaged while the engine is running?

No, in the AFN (and also in the Polo), it's mechanically implemented in the ignition switch, which only allows the key to be turned one position further from the "ignition on" position to start the engine.

With the button, I could immediately start playing again after pressing it, but the MSG simply wouldn't let the motor start.

(I implemented a feature to disable the button while the engine is running by monitoring the voltage at the alternator terminal for charging control.)

@Ulrich

If you have a DWA (recognizable by the red LED next to your door pin), I suspect you're experiencing the same problem I had back then.
The control unit for the windshield wiper system is located under your light switch on the dashboard. It takes some fiddling, but you can get them out after removing the light switch and some of the surrounding panels.
In this case, simply check for loose solder joints or, if in doubt, completely resolder (have them resoldered).

Hello Ulrich,

Hmm... a lot of questions. I'll provide more details (see my previous emails).
above) several things:

1.) In my case, it was definitely the case that bridging relay 109 with a switch...
'Nothing worked: that only helps if the relay itself is broken.' Is there a...?
However, if the error is located elsewhere (e.g., DWA), bypassing the relay may alternatively lead to...
a) extremely erratic engine running.
b) no noticeable change.
c) Possibly, occasional brief jerking.

In the workshop, it was noticed that the problem arises when the cables are moved within the dashboard, or disappears when they are not. However, it shouldn't be worth the effort to fix, or it would be too complicated and therefore too expensive. 'The wiring diagram is so difficult, requiring constant flipping through pages... blah blah...' At that time, I was unfortunately traveling, and my wife had to deal with those guys. (I have the feeling that they probably want to sell me a new one, even though the current one is otherwise still in good condition.)

2.) The main wiring harness that runs to the dashboard tends to...
to cause cold solder joints on the circuit board (due to poor...
soldered connectors and faulty strain relief). This results in the following:
funniest effects (all the lights turn on, displays show nonsense, etc.).
The solution is to expand the A-board and resolder the central connector.
It might be possible with some tinkering, even without removing the steering wheel or airbag.
If a 'shock' helps you, I would definitely try it here.
check it out - even though that's probably not the cause of the engine stalling.
is.




- What signals must be present before the MSG in order for 109 to be activated? If channel 109 is not activated, it appears that the MSG indicates this by continuously illuminating the preheating indicator.

- Which of these signals causes the MSG (presumably a system or device) to shut down the engine or reduce its power to the point where it stops, when the signal reappears?

- What missing or incorrectly received signal causes the MSG (Motor Control System) to make the glow plug indicator blink, even when 109 is activated (simulated by my switch), and simultaneously causes the MSG to stop the engine (how), even though it has been prevented from accessing the engine via 109 because 109 is bridged?

- Is there something like an emergency stop? If so, what are the triggering causes?

3.) I'm not sure what all there is, but there's a missing signal from the DWA (very deep).
installed in the cockpit - supposedly to help against thieves ) achieves a similar effect:
The engine control unit (MSG) shuts off the engine, relay 109 deactivates, and - depending on the situation - the preheating system.
The LED is lit or blinking. Take a close look at the DWA: cold solder joints.
defective relays, etc. (in my case, it was a relay). Okay, and don't forget to have a wrench handy:
Sometimes, when working on the DWA (presumably a piece of equipment or project), things can go wrong, and in those situations, a well-maintained [item/tool/approach] might be the only solution.
Terminal 30 reset (disconnect the battery). The 'Rausschrauber' tool from DWA is quite annoying, actually.

Good luck reviving your Passat.

Martin.

Hello,
I have to revive this thread again.
My 1994 Passat 1Z is also not immune to electrical problems.
After neither of my two machines started this morning, I immediately knew what I would be doing today.
'Good 1z: The preheating light is constantly illuminated and does not turn off as usual. The starter motor is running, but the engine is not starting.'
According to the wiring diagram, troubleshooting: Relay 109 is not switching (already replaced) - Terminal 30 is present, but the ground connection from the MSG is missing.
I quickly bypassed the working contacts of the 109 relay, and sure enough, the light went out and the engine started. Test drive I.O.
Later, the 109s were brought back in, and everything went back to normal as if nothing had happened. The bridge stays in the car, readily accessible for any situation.
This has happened before, but it eventually got better. I don't think it will improve this time.
DWA is definitely something to exclude because it's completely bypassed.
After reading the last few articles, it's probably not related to the MSG or cables.
Who can help with this?
I am grateful for any suggestions.

PS: In the other car, the battery was dead.