Have been looking into the MY 98+ oil temp sensor, which is located in the oil sump drain plug. Realize this is an aged post but I was wondering if any additional info has turned up in the meantime, and I have a question.
Specifically, given the lack of technical documentation, I am theorizing the oil temp sensor is in fact connected to the ECU and not directly to the dash tell tale lamp. Following is the thought process.
That tell tale lamp serves 3 functions, it indicates:
1) low coolant level
2) high coolant temp
3) high oil temp
If condition (1) occurs the lamp is lit solid ie no flashing. I believe the lamp is connected directly to the coolant level switch in the coolant reservoir, which could enable the steady lit indication by simply providing the path to ground (the lamp itself is supplied with 12v).
If conditions (2) or (3) occur the lamp flashes. It seems very unlikely this could be enabled directly by a physical sensor/switch. But it could be enabled by the ECU logic where the ECU provides the ground path. The wring digrams show the coolant temp sensor is connected to the ECU. So it's most likely the oil temp sensor is connected to the ECU as well, and not directly to the tell tale lamp.
The oil temp sensor could be a simple on/off switch or a variable resistance (thermistor) device.
My question is does anyone know which it is? And if it's a thermistor what is the range of resistance values?