Hi
Do you have a Workshop manual? It has the wiring diagrams.
Here is the relevant excerpt.
The Oil pressure switch is connecting to ground when engaged. So, to what condition are you generally referring to: Engine off (switch open) or engine running [normal] (switched to ground)?
What is your actual problem in the back to ask this question?
Suspecting EDIC or Oil sensor switch defective?
WB white-black is usually negative/ ground lines.
Red is hot positive (there are two on 70s: thick direct from battery via fusible link, and thin to feed into Edic-motor).
Y yellow, G green & L blue also feed into the EDIC motor.
BW black white is positive from ignition.
The cable going into the EDIC from the oil pressure switch is YB yellow black (as seen on the pic:yours has the original colorcode).
BY black yellow is the fuel shutoff signal line.
When disconnect from the relay, the lines can only make contact somewhere 'in the back of the harness', which is generally possible for negative/ ground lines, which all join on the chassis at some point during operation.
Usually lines do not get interlinked within a connector itself, but only within the connected device. (Here: The EDIC)
But I'm pretty sure the YB oil pressure line should be isolated from any other line of the connector as it actually is a ground line, athough switched by the pressure switch, whitch makes it a sensor line the EDIC shall react on. If it has contact to any other line, this [normally] could only be the case when the switch is engaged.
This however should only happen when the engine is running, which should only happen with the EDIC is operating properly, which would require the connector to be properly connected ; thus NOT when engine off and connector pulled.
You can test the Oil sensor switch in conjunction with EDIC like this:
1. Disconnect switch. Measure connectivity of switch contact to ground with engine off: Should have no contact.
2. Start engine with sensor disconnected: EDIC should shut-off engine after a few sec.
3. Connect the sensor cable to ground (= bypass sensor switch) and start engine: Engine should continue running. (Be sure engine is ok and oil pressure is generally ok).
4. Measure connectivity to ground on sensor, with engine running, but with sensor bypassed: Should have contact to ground as oil pressure is present.
1. and 4. tell malfunction of the sensor switch.
2. and 3. give ideas on proper EDIC function.
Unfortunately I have no info at hand on how the EDIC-relay and -mechanism itself works.
There might be more service and diagnosis information in the manuals engine electrics sections.
I hope this helps a bit.
Good Luck
Ralf