Is it Possible to Bypass the Oil Pressure Sender Without Dash Warnings?

Clocktower07

Clocktower07

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I’m encountering periodic low oil pressure readings while stopped and I've tried most of the common fixes.

Every couple of days, my oil pressure gauge drops to 0 at stop signs. This reading is accompanied by a single chime and the CHECK GAUGE light. When I start going again, the needle returns to the 12 o'clock position and the light extinguishes. Once the issue starts, it repeats at every stop until I stop/restart the engine. After restarting, I can potentially continue the rest of the trip without getting another low pressure indication. Of note, the PO had a manual oil pressure gauge on the jeep and said the readings were normal according to the FSM. At no point do I sense any issues with the engine that indicate it is actually being starved of oil.

Here’s what I’ve done so far:
-Changed the oil and filter / now running Pennzoil 10W30 with a Purolator Filter
-Replaced the sending unit with a MOPAR OEM unit
-Removed the instrument cluster, cleaned pins/contacts for the connectors, coated everything with dielectric grease, and reinstalled

The descriptions of the oil pressure sender in the FSM remind me of a switch. Is that what it is? If so, is there a way to bypass the sender that does not produce a low pressure indication and CHECK GAUGES light? I would like to install an aftermarket oil pressure gauge and monitor the pressure the old-fashioned way…unless there’s a better way to skin this cat.
 
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I don’t know if this helps much, but yes there is a way because my 2000 2.5 has a plug in the block where the oil pressure sender goes. I get no dash warning lights and the oil pressure gauge reads 60 and never moves.

The PO set it up like that so I can’t help on how it works though.

I tried to take the plug out and put a new sender in because the connector is just hanging there. I thought it would be simple but it was too tight an area for me to work because of the AC compressor.

After busting my knuckles and hands up… I finally just said to heck with it and left it like it was.
 
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Having the same issues. Tried several sensors including an allegedly Mopar from Amazon...which is now misbehaving.

Running Pennzoil and have run Napa high mileage conventional oil.

Have manually verified pressure. Also thinking of putting in an 1/8" T and a manual gauge.

I've looked at the bearings too when I put in a rear main.

Think I am ordering a Standard Motor Products PS284 for my 97.

I also need to completely remove the engine harness and deloom it and inspect and tone out every inch.

-Mac
 
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macleanflood said:
Having the same issues. Tried several sensors including an allegedly Mopar from Amazon...which is now misbehaving.

Running Pennzoil and have run Napa high mileage conventional oil.

Have manually verified pressure. Also thinking of putting in an 1/8" T and a manual gauge.

I've looked at the bearings too when I put in a rear main.

Think I am ordering a Standard Motor Products PS284 for my 97.

I also need to completely remove the engine harness and deloom it and inspect and tone out every inch.

-Mac
Click to expand...

Could this be an issue with the cluster itself? I'm thinking of swapping out my original unit with a spare to see if the malfunction remains.
 
In your 05, it's just a switch that indicates you have at least 6 PSI and the PCM moves the needle to the middle area of the gauge.

I think the FSM has the test procedure in it. But if you disconnect the sender, the gauge should either go mid range or L, and if you ground the connector it should go to the other position.
 
JKP said:
In your 05, it's just a switch that indicates you have at least 6 PSI and the PCM moves the needle to the middle area of the gauge.

I think the FSM has the test procedure in it. But if you disconnect the sender, the gauge should either go mid range or L, and if you ground the connector it should go to the other position.
Click to expand...

This makes 100% sense and should work in the real world, but I'm getting a 0 psi indication with the connector disconnected OR grounded. The connector has 12 volts on it - perhaps "something" happens in the sender and the PCM is looking for another value?
 
I had a similar problem on my 97. I replaced the sender with a standard motor products, same behavior. Then I changed out the oil pump and never had a problem since. In hindsight I wish I would've run with a mechanical gauge to compare my dash gauge with the real gauge.

Related, but we put a new to us 4.0L on a 98 XJ and the oil pressure gauge gave us fits. I can't remember the exact specifics, but the essence was that the wiring diagram said it was a 3 wire sensor but the harness was only a 2 wire. It would read fine, then it would zero out. Then it would read fine. Then it would drop. Completely random. Probably not your issue but I figured I'd mention it.

Clocktower07 said:
This makes 100% sense and should work in the real world, but I'm getting a 0 psi indication with the connector disconnected OR grounded. The connector has 12 volts on it - perhaps "something" happens in the sender and the PCM is looking for another value?
Click to expand...

I thought that sensor was looking for a 5V reference signal, not 12V.
 
Google

Chrysler TSB 08-36-99. It applies to intrepid and 300 models but I’ve seen it work on other models. I wouldn’t bother getting the part listed in the tsb, just take the little plug that seals where the missing wire is out and leave out the seal that seals the connector to the sending unit. The bulletin says it needs to be vented but doesn’t explain why, I don’t know why either but it wouldn’t cost anything to try and I’ve done probably 15-20 and it works​

 
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hear said:
I had a similar problem on my 97. I replaced the sender with a standard motor products, same behavior. Then I changed out the oil pump and never had a problem since. In hindsight I wish I would've run with a mechanical gauge to compare my dash gauge with the real gauge.

Related, but we put a new to us 4.0L on a 98 XJ and the oil pressure gauge gave us fits. I can't remember the exact specifics, but the essence was that the wiring diagram said it was a 3 wire sensor but the harness was only a 2 wire. It would read fine, then it would zero out. Then it would read fine. Then it would drop. Completely random. Probably not your issue but I figured I'd mention it.



I thought that sensor was looking for a 5V reference signal, not 12V.
Click to expand...

The 05-06 FSM references a three-wire sending unit supplied with 5V, but (by all appearances) I have a one-wire sending unit supplied with 12V...
 
That part of the FSM is incorrect.

Pull up the powertrain section of the FSM with the codes for the test procedure.

Not likely your problem, but you can also run the cluster test. Push and hold the trip odo button and turn the key on. Release the trip odo button and the gauges and lights will run self test.
 
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Steve04 said:
Google

Chrysler TSB 08-36-99. It applies to intrepid and 300 models but I’ve seen it work on other models. I wouldn’t bother getting the part listed in the tsb, just take the little plug that seals where the missing wire is out and leave out the seal that seals the connector to the sending unit. The bulletin says it needs to be vented but doesn’t explain why, I don’t know why either but it wouldn’t cost anything to try and I’ve done probably 15-20 and it works​

Click to expand...

This is very interesting. There seemed to be a lot of disagreement on the Intrepid Forum about whether the "vent" was actually a modified resister. Either way, it couldn't hurt to try...
 
I wanted to post a quick follow-up since I know others are having similar issues. As @Steve04 suggested, I removed the plunger that blocks the unused port of the oil sender plug and omitted the weather seal from the rear of the plug. PROBLEM SOLVED. I've daily-driven the jeep for the past two weeks: no fluctuating/low oil pressure, no check gauges light, and no chime!
 
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I know this is an old thread, but this solution absolutely works. I tried multiple sensors, a new pcm (I had to replace it anyway), and a new gauge. Ultimately, I installed a third party gauge. After modifying the connector to allow air in and out by removing those seals it worked. I guess the air pressure in the plug was interfering with the sensor diaphram.
 
paulj215 said:
I know this is an old thread, but this solution absolutely works. I tried multiple sensors, a new pcm (I had to replace it anyway), and a new gauge. Ultimately, I installed a third party gauge. After modifying the connector to allow air in and out by removing those seals it worked. I guess the air pressure in the plug was interfering with the sensor diaphram.
Click to expand...

Do you have a picture of what you're describing?
 
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