I my case at least, the exact test described gives two different results depending on whether the bike is running or not (ignition on).
When engine is running, grounding the wire causes the light to come on. (Which is what we would expect)
When engine is not running, but with ignition on and check sequence complete, grounding the wire does not cause the light to illuminate.
This is what confuses me, what is the difference between engine running and not running. Voltage?
As you say, there has to be a function within the ECM/Instrument cluster to provide a ground path for the self test. That bit works, as the light comes on briefly.
I presume there is then a relay or switch of some kind to change from 'self test mode', and you would assume this switches to 'live mode' (using the oil pressure switch).
But if it switches to live mode, and we've proved all of the following:
- grounding the switch wire causes the light to come on when running
- the switch body is well grounded
- the switch contacts are normally closed
- the switch contacts do not open until engine is started
Then why would the light not come on..