Ecu repair, can a home mechanic repair

The sensor that triggers it maybe faulty connect disgnosis and see the temperature that the sensor sends info to the ecu
Your dash knows ur temp but the engine ecu doesnt it might sends a -40 c signal :)

This problem is with ecu / ecm= engine control computer. These are a common and horrible problem on vw's, particularly on tdi's. The signs in a tdi are when car dash lights come on, but no glow plug light,trans gear lights flash, but car still tries to crank. And hopefully ecu has enough power to out out code u0100= no communication with ecu. Unfortunately the ecu will need to be replacd. The ecu is located under the hood, near and under the wipers. Used ecu with same codes run $50-200. New $1000. If get used one make sure has a return policy. codes must match production quarterly year.

Jetta?You mean Bora!The computer (ECU) is in the middle of the compartment where the windscreen wiper motors are.

lift back seat and look for the inspection flap ,then you can access the unit

WHEN EVER YOU DISCONNECT BATTERY PCM LOSE MEMORY WHICH CAUSE POOR ENGINE PERFORMANCE.TAKE CAR TO VOLKSWAGON DEALERSHIP LET THEM REPROGRAM IT.

Then you must check up the A/C compressor electrical supply. First time the A/C fuse. Second time verify if A/C installation if refrigerant (R 134a type) pressure is OK. The best idea is to scan the A/C (or climatronic) ECU (Electronic Control Unit) memory by internal faults using diagnostic equipment connected to the Data Link Connector (DLC) of the car. For example could be the A/C pressure sensor out of order, and therefore A/C compressor does not have permission for starting. After faults reading you will be able to replace & repair damaged pieces, and erase & reset the A/C ECU.

Check your starter lead at the starter?

You can check for 12 volts there with a multitester and then you can jump the starter direct and see if it turns over without involving the ignition key or related circuits.

If you had your battery disconnected during this repair maybe the ecu needs to be rekeyed to your security keys code? You would have to check with VW on this one for specific procedures.

Good luck and be careful.

Yeah you should since a tune up is required every 30,000 miles.

Don't know much about VW but if it's fine, and it doesn't happen again I wouldn't worry about it. If it does try resetting the ECU by removing the battery terminals and touching the positive lead(red wire) to the negative battery post. It might spark a little, this is just the capacitors discharging, resetting your ECU and starting over. It's like restarting your personal computer

Has to be done at a dealer. Special tool needed.