No Communications Error using VCDS Tool

[jagjot]

I have VW Polo 1.6 16v GTI, Year 2000, 6N2.

My car runns fine with no issues...

I wanted to install cruise control and configure key fob/key (i only have 1 key) in my car. According to tutorials after hardware stalk installation - i needed to enable cruise control from VCDS / My Car's ECU.

I thought the best place to start will be connecting to OBDII connector of my car and see the option - if i have there. So, i bought the VCDS software and realised i am getting "Link Error" / "No Communications Error". I took the car to 2 different garage's and they have same error and they couldnt connect. I also noticed - my engine management light was not showing when i put my key in and turn into ignition (garage told me its ecu problem). Looking at forums i realized its is ecu issue...

Well then i bought the whole kit from ebay seller (taken out of same car as mine). i got Clocks, Comfort Modele, ECU, All the locks and key remote (2 button - 1 key only).

Changed all the above in my car :
1: Good points: I got my engine management light on (scanned my car using VCDS and got lambda sensor errors). nothing serious.
2: If i take out my keys and head lights left on - i will hear a buzzer sound. (was not working earlier)

Bad points :
Key still not working.

I thought i fixed the problem.

Took my car to local vw speacilist garage - thought they might be able to configure the key for me. but they got no communications error - when they tried to go into engine (using vcds) but they could go into ABS.. i thought its their software. next day i took my laptop with my VCDS to them and i got same error. Strange - its started working when i changed all of the ECU/parts. something went wrong again....

Only one thing left to change the full wiring harness inside the car. which will be my last resort. Now i dont know what's wrong with my car. Any help will be appreciated.

Cheers
Jag

[alexperkins]

Is your battery voltage low?

I would say if it isnt youve got a bad earth, a blown fuse or some corroded wiring somewhere

[jagjot]

I checked all the fuses in the fuse box and in engine (on top of battery) they are fine.

Good point :
How to check for bad earth and where? I remember one of the garage connected 2 tools to check on was VCDS and other tool was very old squarish box thing with green (old style - like calculator) screen on it. and it showed bad earth error. How to check the earth???

Regards
Jag