Oil Pressure Gauge / Sending Unit / Gauge Cluster Question

John Scoggins

TJ Enthusiast
Oct 23, 2018
134
Houston, TX
Interesting issue, for me anyway, 2004 TJ, 4.0 auto here. While driving the oil pressure gauge went to 0pis, Check Gauge light comes on. Pulled over and listened to the engine, no noise to indicate that there was 0psi oil pressure. Waited about 15 min with the engine running, then the gauge went back up to the center position (I know it is really an "idiot" gauge not reading true pressure) and no more issues driving home.
Once I got home, with the engine running and oil pressure gauge in the middle I disconnected the connector on the oil pressure sending unit, but no change in the oil pressure gauge it was still showing in the center. I let it run like this for 20-30 min, restarting it a few times and the gauge always read in the center each time. I then performed the instrument cluster self test and got the b0, b8 and Panel Open errors. After running this test, when the vehicle was started, with the sending unit still unplugged, the gauge then read 0psi. I plugged the connector back on the sending unit with the engine running, the gauge still read 0psi. I then restarted a few times, with sending unit plugged in, and the gauge stayed at 0psi. I ran the instrument cluster test again (sending unit plugged in), got same errors, then restarted and the gauge went back to the center.
My plan is to remove the instrument cluster and clean the connectors behind it, but are there other connectors that I need to look/clean?
 

JeepZilla380

TJ Addict
Ride of the Month Winner
May 30, 2017
1,032
Atlanta, GA
Something similar happened recently with my LJ, on start every once in a while the CEL would come on and Oil pressure would show zero, but everything sounded fine. Ordered a new Mopar oil pressure sensor from Amazon and haven't seen the issue since. In my case the 14 year old sensor was just on its way out. Do get the Mopar part if you decide to swap yours.
 
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John Scoggins

TJ Enthusiast
Oct 23, 2018
134
Houston, TX
My thought was the sending unit also, but then I found the communication errors and the fact that when I unplug the sending unit while the jeep is running, the oil pressure gauge does not respond.
 

JeepZilla380

TJ Addict
Ride of the Month Winner
May 30, 2017
1,032
Atlanta, GA
My thought was the sending unit also, but then I found the communication errors and the fact that when I unplug the sending unit while the jeep is running, the oil pressure gauge does not respond.
Thats what I get for multitasking! I haven't removed my dash cluster yet, but I know a few people on here have to replace the lights, etc.
 
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John Scoggins

TJ Enthusiast
Oct 23, 2018
134
Houston, TX
Took the cluster off and cleaned the two connectors. Now the airbag light comes on like it is supposed to, during initial start up. The cluster test still shows b0, b8 and panel open but I am not sure how to clear those, or if they will clear over time.