There are two knock sensors, one for each bank, and are bolted to each side of the block midway along.
Sensor 1 should be associated with bank 1 (1,3,5) so will be the drivers side. The wire comes up from behind the alternator, around the aux belt tensioner and plugs in at the cable tray. Check that it is free and not trapped all the way from the connector to the sensor and check for damage to the cable outer. It is a screened cable so shorts out if squashed or trapped.
Do check that your EML comes on with ignition and goes out independently of the oil light....the bulb may be blown or missing, or someone may have wired the EML to the oil light to hide a problem.
If the EML is not lit then there are no faults at present (ie right now), there may be codes stored but these will be from faults that were intermittant (in the past).
The 19 tells us that your crank sensor signal is degrading but hasnt actually failed yet so unless you want to get stuck...change it.
If the EML is not coming on during the 'misfire' then I would go for the DIS. Yours should be the early type and E-bay is OK but buy new.