Hello all, I have a 2003 350Z, and the oil pressure gauge is maxed out. The day before it was maxing out, it was reading 90 PSI at idle, at operating temp, in about 70 degree weather. And giving even a little gas would read over 120PSI.

I had another oil pressure sensor laying around from my other engine, and I switched them out, and it still does the same thing. With the engine off, if I turn the key to the run position (not starting the car) the oil pressure reads over 120 PSI.

If I unplug the oil pressure sensor and turn the key to the run position, it reads 0 PSI.

Everything I can find and think of, says it's a bad oil pressure sensor. But I just don't know. I did add a quart of 5w-30 Castrol GTX Magnatec oil, my oil level is in between max and min marks.

 

If the oil level is correct, the main suspect is a faulty Oil Pressure Sending Unit.

Is it possible that both units you tested are not working correctly?

 

Could be a bad sending unit, but it could also be that the stepper motor in the gauge pod is glitching out, or even a possible wiring fault. These Zs are getting old now and it wouldn't surprise me if we start seeing stepper motor issues with the gauge clusters. Take the Z to a mechanic and ask for verification. They should be able to hook up a mechanical pressure gauge where your sending unit is now to get an accurate reading.
-Icer

 

• I agree it could still be a bad sending unit.
• Stepper motor? When I hear stepper motor I think of a CVT transmission. This car is a manual 6 speed, and transmission is not related to the issue. Perhaps I am misunderstanding something here.
• Possible wiring fault - What kind of test can I do to check this? My sending unit has 3 wires at the harness, I would assume there is a ground wire, signal wire and reference wire?

Yes, yes it is possible. But I am wondering if it could be electrical

I appreciate the help so far guys!

 

I see your point, but wouldn't we have more reported problems with gauge pods if this was the problem instead of individual component failures (i.e., the Oil Pressure Sending Unit)?: dunno:

The one solid feature I have seen with the 350z is the reliable cluster gauge. The only way to goof this up is not connecting the ribbon correctly.

I trust people with more experience than I have to answer this question.

 

Stepper motors control the needles in modern gauge clusters. Usually domestic cars have issues with these (GM mostly). I mention checking the oil pressure with a mechanical gauge to rule out actual problems with oil pressure (clogged oil passages in the block/heads) and to confirm that you indeed have an electrical fault or bad sending unit. Testing for continuity between the sender and the wiring harness in the dash is the best way to rule out a wiring fault, I'm guessing the wires are power, ground, and signal. To achieve this you will need to get ahold of the FSM's wiring diagrams and have a basic multimeter (in short, lots more work that may not be worth it...read on).

After reading some other posts about this issue, the most common cure is simply replacing the sending unit (about $20 from Z1). Does the oil pressure gauge sit at 0 when you have the key in the pre-start (Accessory) position? Or does it immediately climb up before you start the engine? If the needle is at 0 that's good/normal, if it shoots up there's most likely an issue with the sending unit. If it was me in this situation, I would just get a brand new sending unit, they're cheap so you have little to lose. If that fixes the problem it will save you hours of troubleshooting. I would also make sure to clean up all electrical contacts/pins in the harness plug. Get rid of any oily grit that could cause voltage issues.
-Icer

 

Need I say more? Don't ask me how I know a clogged screen on your pick up tube CAN cause pressure to increase.