I'm not convinced my O2 sensor is working. However if it has failed, apparently I should be getting a "code 15" on the "check engine" light. Sources - Haynes manual & the Garrett Performance Handbook. Both indicate that this is the case for pre 1995 cars (which mine is) - the 1995-onwards OBDII system means a fancy diagnostic thingie is required.
Now that's all well & good - but my instrument panel doesn't seem to have a "Check Engine" light.

So am I missing the blindingly obvious, misreading the information or is something else going on ? Is there another method for engine diagnostics (specifically O2 sensors)?
FTIW I took a look at David Moughtin's 1991/2 car today & it too is missing the elusive "check engine" light.......

Regards,