Checking ECU Readings

How can i got about reading what the ECU is seeing from the engine sensors.

If i want to read back the readings from the following sensors at idle;

- Water Temp
- Oil Temp
- Oil Pressure
- Knock Sensor

My fan comes on constantly and want to understand why so reading back what the ECU sees might help a lot.

also trying to understand why some of the gauges are not working even though the sensors have been replaced with new items.

Someone has not linked out the trinity switch. Is air con removed ? If so is switch turned off ? As linking it out was done to bring fans on constant. Which gauges don't work ?

How about something like this to read

Hold on while I try and find link

http://www.gtir-motorsport-club.com/t6348-nissan-diagnostics-on-windows-and-android

Go back to thread you had on this as had all info/suggestions needed really.
Ideally you want consult 1 , either the grey ones like found on net or the module chap on this forum does, you can check sensor values to some extent via dmm at ecu inputs but obd1 is simple way .
Out of sensors you list only water and det goes to ecu. ecu does not read oil temp or pressure.
Oil sensors would be dmm check at harness to centre console gauges .