My oil pressure gauge is acting up, not sure why

caminonut said:

Do you mean by gauge motor you’re talking about the step motor?
Also, if you replaced it, did you check the shunt resistor on the back of it for continuity?, and check it for a Ohms reading.
Also check any of your grounds they’re very important.

Click to expand...

1998chev454 said:

also if it’s not mechanical what would it be circuit wise ? Cause I have replaced both sending unit and the gauge motor in the cluster and cleaned the connections that go from the truck into the gauge cluster, so I’m not sure what else there could be

Click to expand...

Road Trip said:

Here's the circuit that you need to verify proper resistance values:

You must be registered for see images attach

0 ohms should give you 0 psi indicated.

45 ohms should give you 40 psi.

90 ohms should give you full scale deflection.

The tan wire physically runs from oil pressure sending unit Pin A, through C200 in the firewall, to Pin 15
at the Instrument Cluster connector. In order for that electric Oil Pressure gauge to work properly,
you need solid power and low resistance ground to the instrument cluster, also the correct 0-90 ohm
resistance coming in at Pin 15. I've attached the Theory of Operation blurb for the Oil Pressure Gauge
taken from the FSM.

Since you've already replaced the sending unit, I'd try to monitor the oil pressure signal and see what
kind of resistance readings you get. And if that gives you rational readings, I'd want to see those
same readings at the instrument panel connector, pin 15.

Q: Does this wiring diagram help?

Click to expand...

1998chev454 said:

that other reply was supposed to be posted earlier but I have found the issue, I checked the ohms at the oil pressure unit, truck on and truck off and truck on showed close to zero resistance on cold start so I am very certain it is that, the ohm reading didn’t match up with where it should have been, so bad part from autozone, thank you guys so much for the help

Click to expand...

1998chev454 said:

that other reply was supposed to be posted earlier but I have found the issue, I checked the ohms at the oil pressure unit, truck on and truck off and truck on showed close to zero resistance on cold start so I am very certain it is that, the ohm reading didn’t match up with where it should have been, so bad part from autozone, thank you guys so much for the help

Click to expand...

movietvet said:

Once you are 100% sure, it is fixed. Go to the #1 post, where you started this thread. Upper right, you will see 3 dots. Click on them. Click on Edit. Go to the thread title and add the word SOLVED and save it. Then when someone sees that and their problem sounds the same, they will read the entire thread and hopefully fix their problem.

Click to expand...

1998chev454 said:

when I get the chance I will replace it and let ya know

Click to expand...

Road Trip said:

Here's the circuit that you need to verify proper resistance values:

You must be registered for see images attach

0 ohms should give you 0 psi indicated.

45 ohms should give you 40 psi.

90 ohms should give you full scale deflection.

The tan wire physically runs from oil pressure sending unit Pin A, through C200 in the firewall, to Pin 15
at the Instrument Cluster connector. In order for that electric Oil Pressure gauge to work properly,
you need solid power and low resistance ground to the instrument cluster, also the correct 0-90 ohm
resistance coming in at Pin 15. I've attached the Theory of Operation blurb for the Oil Pressure Gauge
taken from the FSM.

Since you've already replaced the sending unit, I'd try to monitor the oil pressure signal and see what
kind of resistance readings you get. And if that gives you rational readings, I'd want to see those
same readings at the instrument panel connector, pin 15.

Q: Does this wiring diagram help?

Click to expand...