My oil pressure guage is whacked. For a long time it hasn't worked, the needle pointed perfectly horizontal to zero at all times. According to the FSM, this is where the resistance on the circuit is infinite (no continuity).

One day while I was poking around under my car trying to figure out why my reverse lights weren't working, I saw a dangling black wire connected to nothing and looking like it had been cut/broken. Well, in my mind, black means ground, so I soldered an appropriate ring connector to it and grounded it on top of the transmission where it meets the engine block.

Next thing I know the oil pressure needle is pegged at the physical maximum, well above 110 and almost vertical. I'm like, whoops, that didn't help. Apparently that ground eliminated all resistance from the circuit. So I disconnected the ground I made. The needle then dropped below zero and hung there at all times, like 15 ~ 20 degrees below horizontal.

I did notice that the oil pressure sensor unit had nothing connected to the little T-shaped nipple, so I tried connecting that same wire to it. The pressure guage started reading like FIVE or TEN psi at all times. I'm like, that can't be right, my car has plenty of power and the oil consumption rate is normal.

So I disconnected that wire again and removed it altogether (it had a single-wire plastic harness that could disconnect). The needle now hangs permanently below zero at that same drooping angle.

Did I destroy the guage or the sensor unit? Does anyone have any knowledge on this issue? Is there a red/yellow wire anywhere on the circuit that's near the reverse/neutral/5th gear switch wire cluster?

Anyone with any useful input would be appreciated. Thanks!

 

There should be a yellow wire with a red stripe and it is in the harness which goes to the starter.It has a funny connector on the end of it which connects at right anles to the the pin on the pressure sensor.

 

I think I saw one such wire down there... Honestly, I saw TWO such wires, each broken, so I assumed it had been cut somehow, so I soldered them together. I saw no right-angle type connector. Is this an incorrect thing to do?

 

The wire that you solder and grounded to the tranny is your wire!! This wire goes to the oil sender, which you already did. Take a look at the gauge itself on the back, cometimes the needles manage to get off the actuator (what moves the needle up and down).

Once you take a look at the back of the gauge, you will understand what I'm talking about, TRUST ME!!

 

Get an aftermarket guage - MAZDA's OE Oil Press guages are notoriously failure prone