AUDI A4 won’t Start and Immobilizer Warning Light on

A car owner drives me a red AUDI A4 2000 year, with 120 thousand km. After repaired in another factory, the car can’t start and the immobilizer warning light on.

Then I connect VAS 5054A with the car to self-diagnose engine, and read out a fault code 17978, which means ECM (Engine Control Module) was clogged. It showed that the engine was forbidden from running by anti-theft system. I checked the ignition key, there was no signs of broken. The car is second-hand and only has one single ignition key, so I cannot tested it with other keys. I logged in anti-theft system (address code25), there was no communication. Logged in dashboard (address code17) and I can successfully entered the diagnostic menu, but it just can read out 14 digital identity code immobilizer system, not 17 digital, the fault code was 01177, it means ECM (Engine Control Module) was not permitted. To remove this situation, I operated like followings. Entered the anti-theft system (address code17), chose matching function (10), filled in “00″, clicked OK and cleaned out the self-adaptive figures. At that time, immobilizer indication light was off. It showed that matching was successful. Tried to start up the car, the engine can work successfully. So, the fault was troubleshot.
VAS 5054 for Audi
The car was placed anti-theft system immobilizer- II, the immobilizer module was integrated in the dashboard, so it’s necessary to enter the diagnostic menu on dashboard. The same problem happens sometimes, it’s caused by the lack of system voltage or repetitive starting. Generally, you can solve this problem by turning on the ignition for a long time or using diagnostic tools like VAS 5054A to clean out the self-adaptive figures instead of change the components.