1994 NAS Discovery, check engine - reset procedure?

[Black Magic]

The check engine light came on when I was running the vehicle (stationary) to get air bubbles out of the cooling system. This was after replacing a thermostat and temp sensor.

I have searched for few hours on how to reset the check engine light both online and in the RAVE CD I got... but I am still not much wiser on how to reset a code 44 - I have info saying this is a Lambda sensor - same as an O2 sensor?

Found lots where a scanner is mentioned - but those are for OBD2 models, not OBD1?

The procedure listed here dosent seem to be working - so I presume the connection or sensor itself is bad?
Check Engine light reset

Under passenger seat
To Clear Faults...
1) Switch Ignition ON -- Do Not Start Engine.
2) Disconnect Serial Link plug, wait 5+ seconds.
3) Re-connect Serial Link plug.
4) Switch OFF Ignition, wait for main relay to drop out (click).
5) Switch Ignition ON and check display unit for further codes to appear. Clear each as above.

It seems the Serial Link plug is the connector that connects the code display to the vehicle?

This would be the first time I have dug into engine issues on a vehicle that has an ECU etc - Older vehicles seem to be so much easier to work on!

[vray]

Resetting the code: those instructions miss one critical detail, the fact that the serial link plug to disconnect is in fact under the glove box. Remove the cardboard panel (carefully) and you will see an off white plug with only a couple if wires if I remember correctly. This is the one you disconnect in the routine you describe.

OBD1 is a very simple system. The codes you get under the seat are all that it provides. (If I am wrong here, someone please correct me.) Simple for some is good, you don't run in the problems an OBD2 system has when something goes wrong.

The code 44 is oxygen sensor left bank, code 45 is right bank. These sensors sense the oxygen content of the emission, and the ECU uses this info (in combination with other sensors) ossillating from rich to lean multiple times per second. If the sensor gets into a closed loop, signalling rich or lean all the time, the code is set. It needs a full minute of a closed loop to trigger the code, so this is not accidental. This is a common code to get and rarely is the sensor itself. Could be something really simple like wrong octane gas (I use 89 gas, 92 gives me code 44 and 45 everytime), not closing the gas cap properly.. Check the easy stuff before you get it diagnosed, 99% of the time it is that simple.