Bad Oil Pressure Gauge

Jpmiller97

Jpmiller97

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Oct 14, 2017
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Commerce Charter Township, MI, United States
I went out and purchased my first tj a little over a month ago and the oil pressure gauge just started to act up. I put a new sending unit and harness in it and the oil pressure gauge still doesnt work. It will read 40 psi then just randomly drop to 0. I know I have oil pressure because I hooked up a mechanical gauge to check it. So is there a way to disable the beeping and the check gauges light if I disconnect it and put an aftermarket gauge? also is there something that would typically cause this issue?
 
Jpmiller97 said:
No. I figured if I was going to spend that much money I'd put an aftermarket gauge in
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That may be your issue there (either that or potentially a faulty unit in the instrument cluster itself). Our TJs are very, very well known to not like any sensor that isn't an OE Mopar sensor.
 
I can't stress this enough but always use OEM (Mopar, GM, Toyota) when it comes to replacing sensors on a vehicle. I see so many people buy aftermarket sensors and they end up not working and then go buy another similar sensor that also fails. By that time they are past the cost of an OEM.
 
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Ahoragi said:
I can't stress this enough but always use OEM (Mopar, GM, Toyota) when it comes to replacing sensors on a vehicle. I see so many people buy aftermarket sensors and they end up not working and then go buy another similar sensor that also fails. By that time they are past the cost of an OEM.
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I was going to get one but then I decided I'd rather get an autometer set of gauges because it seems like those sending units don't last
 
Jpmiller97 said:
Do you know if the signal from the sensor goes straight to the instrument cluster or does it go through the pcm?
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I'm not entirely sure, but you could find out for 100% certain by checking the wiring diagrams in the FSM. You can download a free FSM here:
Jeep Wrangler TJ Factory Service Manuals (FSM) & Technical Documentation

But like @Ahoragi mentioned, you always, always, always want to use OE Mopar sensors on these things. That very well might be your issue, not even kidding. These TJs almost always refuse aftermarket sensors. They're notorious for finicky electric systems.
 
Jpmiller97 said:
Thinking to stop the beeping I'd just ground out the sensor wire and put a 35 ohm resister on it or something so it still reads pressure and doesn't think it's zero?
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I'm not much of an electronics guy, so I can't comment on that. Your idea sounds about right though.

Isn't that sort of just putting a bandaid on it? Wouldn't you rather fix it the right way?

But I mean if it works for you, then who am I to object :D
 
I have the same issue and it's been going on for two years. I think it's related to buying my sending unit from autozone. Mine was at 0 when I bought it. The guy I bought it from told me that the sending unit had been replaced so it was probably the gauge. I figured I would try the simple solution first. I bought another sending unit. I noticed it was the exact same one, meaning the PO had also gotten his from AZ. I put it in and it worked like a champ . . . for six months. Now I am going to replace it with an OEM unit. Mine reads fine, then drops to 0, back up again like a yo-yo.
 
Chris said:
I'm not much of an electronics guy, so I can't comment on that. Your idea sounds about right though.

Isn't that sort of just putting a bandaid on it? Wouldn't you rather fix it the right way?

But I mean if it works for you, then who am I to object :D
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I understand what you're saying I'm just trying to figure out how to get this beeping to stop when I remove the sending unit and go with an aftermarket gauge. I'd rather have an accurate set of gauges that I know I can trust than the oe ones which I've never found reliable
 
HongKongDrifter said:
I have the same issue and it's been going on for two years. I think it's related to buying my sending unit from autozone. Mine was at 0 when I bought it. The guy I bought it from told me that the sending unit had been replaced so it was probably the gauge. I figured I would try the simple solution first. I bought another sending unit. I noticed it was the exact same one, meaning the PO had also gotten his from AZ. I put it in and it worked like a champ . . . for six months. Now I am going to replace it with an OEM unit. Mine reads fine, then drops to 0, back up again like a yo-yo.
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Yup that's what mine does just up and down. Once it stayed down and that's when I got worried
 
RussTJ said:
I'm having a similar problem. Just confirming that I need an OEM Oil Pressure Sending Unit?
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Yes, stay away from store brand sensors. Mopar is the way to go for sensors with the exception of O2 sensors where NTK is the OEM. It took 3 trips to Autozone one Sunday many years ago when the Jeep dealer was closed before finally getting an oil pressure sender that worked properly for my son's Grand Cherokee. He cracked its block a few months later. :eek:
 
Jerry Bransford said:
Yes, stay away from store brand sensors. Mopar is the way to go for sensors with the exception of O2 sensors where NTK is the OEM. It took 3 trips to Autozone one Sunday many years ago when the Jeep dealer was closed before finally getting an oil pressure sender that worked properly for my son's Grand Cherokee. He cracked its block a few months later. :eek:
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Thanks Jerry. Just ordered it.
https://parts.moparonlineparts.com/...3cmFuZ2xlciZ5PTE5OTcmdD1zZSZlPTItNWwtbDQtZ2Fz
 
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I have the same issue with my oil pressure. Jeep runs great with 168k miles, but after driving home from work 30 minutes in 90 degree weather, last 10 minutes going up the mountain 2000 feet, I pull into the driveway and oil pressure gauge starts bouncing low and back to normal. Check engine light come on then off. What's up? I put a mechanical gauge on pressure reads fine. Engine running I unplug the sending unit and it still reads oil pressure. I'm guessing memory in the PCM. Cycle key off then start it back up still reads oil pressure. Cycle key off again, take out key and then start engine reads no oil pressure. It's got to be memory in the PCM. How do I bypass the oil pressure sending unit with the 1 wire? So the check engine light will not come on. I want to install an aftermarket meter (Auto Meter Stepper Motor Gauge) in the same location so I can get away from this dummy gauge.
 
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Jerry Bransford said:
Yes, stay away from store brand sensors. Mopar is the way to go for sensors with the exception of O2 sensors where NTK is the OEM. It took 3 trips to Autozone one Sunday many years ago when the Jeep dealer was closed before finally getting an oil pressure sender that worked properly for my son's Grand Cherokee. He cracked its block a few months later. :eek:
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Hey Jerry, any ideas whats going on with my oil pressure? I have the same issue with my oil pressure. Jeep runs great with 168k miles, but after driving home from work 30 minutes in 90 degree weather, last 10 minutes going up the mountain 2000 feet, I pull into the driveway and oil pressure gauge starts bouncing low and back to normal. Check engine light come on then off. What's up? I put a mechanical gauge on pressure reads fine. Engine running I unplug the sending unit and it still reads oil pressure. I'm guessing memory in the PCM. Cycle key off then start it back up still reads oil pressure. Cycle key off again, take out key and then start engine reads no oil pressure. It's got to be memory in the PCM. How do I bypass the oil pressure sending unit with the 1 wire? So the check engine light will not come on. Is it SU open or closed? I want to install an aftermarket meter (Auto Meter Stepper Motor Gauge) in the same location.
 
Same issue for the past week. We put a mechanical gauge on and at idle hot it reads 10psi, Jeep says it should read 13psi. We changed the sender but no improvement, when hot at idle the dash gauge often drops off and all the alarms sound off. Rev it a bit, the pressure jumps up and the gauge goes to normal.

I'm thinking oil pump or is there a high pressure bypass which might stick open?

In the shop with the mechanical pressure gauge the alarms never went off.
 
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Update: It's only been a week, but everything seems to be okay now with my oil pressure gauge. 2004 Jeep Wrangler 4.0L. First step I change the oil pressure sending unit with a MOPAR replacement, had no change. So whats different I ask, the same week before gauge problem I had a complete exhaust system from manifold back installed (stock) $1200.00. New NTK O2 sensors about 6 months prior (I was popping bank1/bank2 codes then). Tested the pressure with a mechanical gauge looked good, but couldn't road test because hose was not long enough. Cleaned the engine block and wiring of all crud (looks amazing now). Installed an aftermarket Auto Meter Oil Pressure Gauge (Stepper Motor, model 3652, this gauge has a .5% variance/accuracy, a mechanical gauge has a 2%) so I could monitor both gauges while driving. Installed an oil filter sandwich plate adapter (Mishimoto MMOP-TPS), so I could install a 2nd oil pressure sending unit (came with the Auto Meter Gauge). Erased all memory in the PCM (I've read major modification like new exhaust, sensors this needs to be done so it could relearn your driving habits) and ran a instrument cluster diagnostic test to make sure cluster was good. Page 1013 of the 2004 service manual says Curb Idle Speed = 13 psi, 1600 and higher RPM = 37 - 75 psi for the 4.0L. I have a link to a (pdf file) service manual if anyone needs it. My final thoughts are: the new gauge is awesome I can actually see the real oil pressure and the sandwich plate has 2 addition ports. I could install a oil temp sensor and gauge no problem. Resetting the PCM I believe was the key factor, because of the new parts. My fingers crossed I'll keep monitoring and post here if I have any changes. If all fails and I get a low oil pressure reading on the factor gauge and check engine comes on, my next step will be a replacement oil pump on an engine with 168k. Also I may install a new TPS and IAC sensor.
 
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