Clarkie GT

ive connected the 2 connectors under the dash, then when i turn the ignition on, i hear the relays and fans cutting in and out, but the engine managment lights up and doesn't flash, am i doig some thing wrong?

andyxros

do it again, ignition on,push throttle peddle full down and then half way for a second or two, let off start up drive off a few yards and it should constant flash, see what happens
just connect the black plugs to see what the light dose for erroe codes before you connect the green ones as above

Splitpin

From what you've said the ECU is in one of its diagnostic modes, so what exactly are you trying to do here? There are three "modes" you can achieve with those connectors.

If you connect just the green plugs and turn on the ignition, the ECU goes into "D check" mode, cycling all the solenoids and relays it can control.

If you connect just the black plugs, the ECU goes into read memory mode. The check engine light will flash out any current error codes.

If you connect the green and black plugs, the ECU goes into full diagnostic mode. All stored ECU parameters (including stored error codes and learned fuel and ignition corrections) are cleared and the ECU will function check all the sensors and electrical hardware.

You need to start the car, warm it up (in order to generate a signal from the lambda sensor) and drive at at least 10km/h for a few seconds (to generate a signal from the speed sensor, assuming a later classic with an electronic one). Provided all of that is done and the ECU is happy it will flash the CEL on and off to confirm.