1999 Jeep 4.0 oil pressure sensor signal wire losing voltage

I took measurements, per what I've learned from SD. The circuitry is good but the signal wire is losing voltage. Have replaced the sensor and it's doing it more often since I did that. After I took the measurements the frequency with which it stops working has decreased. This appears to be a circuitry problem but am not quite sure how to diagnose whether it's the circuit or the computer. I am assuming the sensor works correctly because a shorted sensor would just not work and not be a intermittent issue and because it's new. The signal wire grounds in the computer and no other sensors are having issues. Thanks for any help

Oil pressure sensor not working correctly. Dash gauge often goes to zero and sets the check gauge's light. 5V reference at computer and at sensor show same voltage constantly. Ground wire checks out, loaded the circuit with a test light. Signal wire shows 2V and then cuts down to about .04 mv and that reading shows at both sensor and at computer. Trying to diagnose further (computer or circuitry problem)

I have wiring diagrams if that helps. thanks

Key On, Engine Off (KOEO)

Disconnect the sensor, what is the voltage on the signal wire?

Are you able to read the Oil Pressure PID with a scan tool? If Yes; Sensor Unplugged,

1. Jumper the 5v Ref to the signal wire, does the PID change to a high or maximum reading?
2. Jumper the Signal to Sensor ground, does the PID change to a low or minimum reading?

If you just have a code reader, either of these should set Signal Circuit High or Signal Circuit low codes.

If the PCM can see the absolute low and high value from the jumpering method, the wire integrity is good, but the sensor is bad.

You stated the dash light turned on, what codes were set in the PCM?

Hey, thanks for the reply. I jumped the 5v to signal wire Key on Engine On (not KOEO) and there was no change. I used a 5kohm resistor to do this and I was getting different voltage readings on the resistor itself. Meaning that I used two T pins (made sure they weren't touching) and then a jumper aligator wire connected to a 5kohm resistor between them. When I took voltage measurements just behind the sensor itself I was reading 5vref (across the aligator jumper wire all the way to 5vref side of the resistor) but then read low voltage on the T pin and other side of resistor - back probed into the signal wire on the sensor. I could not get the 5v to register on the signal wire using the resistor. I did not try to just jump it without a resistor. I assumed I was getting some kind of voltage drop across the resistor. I meant to mention this. I didn't try to jump the 5vref to the ground side though. The dash gauge just says "check gauges" and does not give a CEL. I would think it would but it doesnt.

....Should I try to do this with the engine off but key on to avoid current flow? Maybe because current was flowing it was dropping the voltage across the resistor and not passing the reference voltage to the signal wire.

Let's back up a bit, what is the problem? The Guage isn't working correctly? or you have codes for the oil pressure sensor?

The checks I suggested must be done, Key ON, Engine OFF. Toss the resistor.

Just use a t-pin backprobed, whilst the sensor is disconnected and use your test lamp to jumper, just don't spread the pins when you front probe with the tip of the test lamp.

Hey, so the problem is that the oil pressure gauge has started to drop out more and more frequently. By drop out I mean I will be driving (personal car) and the gauge will fall to 0 or very low pressure. At first I thought that I had a clogged pick up or something internal but I put a manual gauge on it while it was reading zero and the oil pressure is fine. It always reads normal after cranking and then within a few hundred yards it cuts out and the check gauges light comes on, but no codes. The sensor has been replaced but it's doing the same thing with a new sensor. I actually broke the old sensor removing it to put a manual gauge on it. I did my voltage checks per SD's instructions and found that the signal wire was were the issue was. It had normal readings.....2-2.4 volts @ around 50 psi oil pressure and increased properly with throttle increases. It suddenly then drops out and there is no corresponding voltage on the signal wire. I will try it without the resistor tommarow without the engine running. Thanks again.

Perform the check I suggested, the Guage should max out and min out. When it goes to min the light should illuminate.

There wasn't a check valve on the manual tester, was there?

If my suggestions prove out, your 'new' sensor is bad.

Try wiggling the wires in as many places possible when performing the 2 tests.