What p20bd faultcode mean

Go here..
http://www.micro-tronik.com/faultcodes/obdiifaultcode_p1b77

Take it to a garage and have them read the OBD faultcodes for starters ... could be as simple as bad electronics/wires, but something more serious too ...

P1685 is:
P1685

Skim Invalid Key

The engine controller has received an invalid key from the SKIM.



You can get a full list of error codes from:

http://www.wjjeeps.com/faultcodes.htm

This link expalains all the codes. Please rate this solution high before clicking on it.
http://www.wjjeeps.com/faultcodes.htm#DTC

If the light is flashing, severe catalytic converter damage and power loss will soon occur.

http://www.wjjeeps.com/faultcodes.htm#MIL

Take it to the dealer, the EPC warning light - and even more the failsafe run which doesn't allow you drive faster than 20mph) is an indication of serious motor troubles. They can read the ECU faultcodes, which should be a good startingpoint for troubleshooting the cause ...

You could do some basic troubleshooting like checking the air filter, the oil level, the spark plugs, etc. You didn't fill it up with bad gas, did you ? And does the engine make strange noises/vibration when running idle ? In case you fixed some obvious cause, you can dis- and reconnect the battery to erase the engine's faultcode. If it's not fixed, the EPC (and failsafe run) will simply come on again.

My advice would be not to drive it untill it's fixed to prevent more potential damage.

Take off the glow plug power bar and check each glow plug with an ohm meter. Infinite resistance means it's burnt out. Check the three glow plugs on the right side of the head with your ohm meter as well.
Just removing and reinstalling the bar will fix any bad connections which might also have triggered the errorcode, so when none of the plugs seem broken, that might have been the case.

I had the same faultcode on my 2005 TDI some years ago; it ran perfectly, but after checking under the hood 1 of the plugs was indeed broken.

That's the motor-management warning light. Meaning: serious errors are being detected by the motor-management computer (= ECU). You should have a dealer readout those ECU faultcodes using VAGCOM to determine the cause a.s.a.p, before (more) harm is done to the engine.

Please be aware that your motor could also switch to "failsafe" mode when too many severe errors are detected, meaning it's terribly slow to drive and turbo-pressure is nearly non-existing.

It means that it didn't receive a signal from the transmision module.
Have your transmission control module checked.

To reset your engine codes:
Remove the negative terminal of your battery (10mm wrench).
Turn your ignition key to START and hold it there for about 15 seconds.
Turn your ignition key to OFF and remove it.
Connect the negative terminal of your battery.

TCM (Trans control Module)
(electronic transmission control module)

http://www.wjjeeps.com/faultcodes.htm#1400

Here's a link to error codes, but the one you listed has too many digits.