VAG-COM: Strange 1Z Reactions & Troubleshooting

Hello fellow enthusiasts,

I wish everyone a happy and healthy new year!

I'm having the following problem with my Passat Variant MKB 1Z, manufactured in 1994:

I've already replicated many adapters that have consistently worked with VW vehicles, but not with my Passat. Now I've tried Maik's adapter, and I have no idea why it's working. Aside from a few 'too many communication errors' and occasional 'can't synch baud rate' messages, it seems to be establishing communication.

Okay, I'm experiencing the following issues: When I select 'engine control unit,' the preheating indicator flashes at different intervals and for varying durations during the connection process. If the engine is already running when I select the engine control unit, the preheating indicator flashes as described above, and the engine 'stutters' (i.e., it briefly revs up for 1/2 to 1 second with significant black smoke). Additionally, error code 65535 (engine control unit fault) is logged in the error memory, and sometimes, error code 777 (short circuit to positive on the throttle position sensor) is also logged. The VW part number of the installed engine control unit is: 028 906 021 B. Furthermore, not all channels are accessible in the adaptation settings.

I temporarily installed a different control unit (VW part number: 028 906 021, which I believe is from a Vento), and with that unit, none of these issues occurred!

'Does anyone have an explanation for this? How can I fix it? I would appreciate any suggestions.'

Hi Joerg,

I just checked something for myself:

Tax device number: 028 906 021 AK

The preheating indicator is not illuminating for me , and when the engine is running, the RPM does not change when logging in . Only a few "click-click" noises can be heard under the dashboard when logging in.

Interestingly, when using Dennis's (GarfieldMZ) adapter, the preheating indicator blinked during the readout. It seems there are differences between adapters . With this adapter, we were also able to generate error code 65535 "Engine computer defective" when the engine computer attempted to set the idle speed with a very rich fuel mixture (1.9 mg/stroke). In this case, there were red errors in all measurement blocks, and error code 65535 was generated. This did not occur with ULF's adapter... however, I also reduced the fuel pump output using VAG-COM.

Best regards, Christian.

haehnlein wrote:

Interestingly, when using Dennis's (GarfieldMZ) adapter, the preheating indicator blinked during the readout process. It seems there are differences between adapters . . .

.

Hi Christian / Dennis,

Do you happen to know whether Dennis' adapter is built with or without an optocoupler?

Evening.

I think I've got it!

'I just downloaded the latest VCDS manual and the section on common VCDS issues, read a bit on the Ross-Tech website, and tried to understand what I downloaded. On the way from the customer's place to the hotel, I experimented a little. Everywhere it mentioned that you should change the 'char_int' setting in the options when you have communication problems. Mine was set to 0. I also found something about changing the 'kw2_delay' field, which I've now set to 10.'

Now, the login works without these 'surges'. The preheating indicator flashes briefly and that's it! It works wonderfully. Also, no more errors are being logged in the error memory! I've tried it with the originally installed control unit 028 906 021 B. As soon as I'm back home (on Saturday), I'll test the other two control units as well! I'm hoping for the same result!

I haven't replaced the 4 C's on Maik's adapter yet!

I would be very interested to hear from other mechanics who also have communication problems, to find out if these changes have had an impact on them as well!

joerg

Hello Christian, hello Ulf!

'I haven't been able to look inside my adapter yet, as it seems to be glued shut by the manufacturer (the electronics are inside the plug housing). Does anyone know if it's possible to determine something about it technically without opening it? Otherwise, I'll have to figure out how to get it open...'

Regards,

DENNIS



Interestingly, when using Dennis's (GarfieldMZ) adapter, the preheating indicator blinked during the readout process. It seems there are differences from adapter to adapter . . ..

Hi Christian / Dennis,

Do you happen to know whether Dennis' adapter is built with or without optocouplers?

joergs wrote:

Everywhere, it was mentioned that when encountering communication problems, you should change the `char_int` option. Mine is currently set to 0. Additionally, I found something about a change in the `kw2_verzögerung` field, which is now set to 10.

Hi Joerg,

Hopefully, it will work for me .

Hi Dennis,

I wouldn't disassemble that part... otherwise, it will be ruined in the end .

Best regards, Christian.

ulf wrote:

Do you happen to know whether Dennis' adapter is built with or without optocouplers?

GarfieldMZ wrote:

Hello Christian, hello Ulf! I haven't been able to look inside my adapter yet, because it seems to be glued together by the manufacturer (the electronics are inside the plug housing). Does anyone know if it's possible to determine something about it technically without opening it? Otherwise, I'll have to figure out how to get it open...

Hi Dennis,

Please measure the resistance between pin 5 of the COM port (GND) and the vehicle's ground connection.
It's likely to be an optocoupler adapter if the resistance is around 100 ohms or higher, and it's probably an adapter without optocouplers if the resistance is below 10 ohms.

I want to revisit this topic!

I had almost the same article posted on the forum of 'auto-intern.' After several weeks, I received a response. Here is the response, which I am posting here without any comments.

'1Z engine control units sometimes require a baud rate of 240 baud. This is much slower than all other vehicles. Sometimes, setting the initial baud rate to 240 can resolve the issue. Newer OBD2 testers, such as the K1-K2, also have an integrated baud rate detection feature, similar to the HEX-COMs from Ross-Tech, which helps to resolve this problem.'
The adapter hardware has to be of good quality.

Oh yes, one more statement! Completely without comment!


hello,
The preheating lamp also functions as the engine control lamp. Please check the brake light bulbs. Some of them use 12V 21/5 watt bulbs, but only utilize the 21-watt filament.
If there's a faulty bulb, you can search for a long time. I once chewed through all the wires in an A4 (for a whole day).