Oil pressure gauge and light??

1997 Cherokee xj. Has an oil psi gauge and light. How does the gauge work with only two wires to the oil pressure switch?? Is it just an “off-on” gauge, or will it sweep with the pressure fluctuations within the rpm range??

Again, that's all done within the ECU.

RCP Phx said:

Again, that's all done within the ECU.

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I get that. Totally understand that the ecm handles all of the functions of the motor.

That being said, a variable sensor that operates a switch and a gauge needs to have 3 wires to make work (ground, 5v reference and signal)....

If my Jeep takes a two wire “switch”, what’s the use of the gauge???

These aren’t useless questions I hope, but it makes sense that an “on-off” switch has two wires , and a gauge (sender unit) has 3.


If my Jeep has a gauge and a switch it should need the 3 wire sender unit.. right??

I believe the oil pressure sender is a variable resistor, all it take is two wires and a regulated, 5-volt supply for the computer to determine the pressure.
Checking Rock Auto, all 1997 XJ oil pressure sensors are two wire. If there was an additional wire, it would go to ground.
AFAIK, all XJs have two terminal oil pressure sensors.
The sensor, when screwed into the engine block, would be grounded, if wired internally that way.
I was not able to find an internal diagram of how the XJ's oil pressure sensor is wired or constructed.

Old ones actually had one wire and ground thru block. A 2 wire is basically the same but has dedicated ground wire instead of thru the body of the sensor. Function is similar to a coolant temp sensor.

The sensor isn't wired directly to the dash. The ECU reads the pressure and tells the dash what to display, including the guage and idiot light. Same for the speed, rpm, etc.