can not read ECU error codes

[Konstantin Bogach]

Last time I looked at stored codes was when I was buying the car (200tqa
MC2  '89). It stored knock sensor code that time.  Check engine light
was missing in the IC and I installed it later.  Since then I see that
it comes on time to time. Knock sensor is torqued properly.  Finally I
decided to address this issue starting from pulling codes. To my
surprise I was not able to get anything,  no even 4444. After I
activated the sequence the bulb and LED (looked at both) connected to
test connectors continuosly blinked 2.5sec on/2.5sec off until I plugged
a jumper in again for 4 sec after which bulb and LED turned off.
WHAT IT MIGHT BE???????
Any help will be deeply appreciated.

Konstantin Bogach.