What in the unholy hell is wrong with my oil pressure? - JeepForum.com
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post #1 of 17 Old 09-20-2017, 06:07 PM Thread Starter
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What in the unholy hell is wrong with my oil pressure?

I've got a '14 JKUR. 57,000 miles on it. Earlier this year I got a CEL indicating my oil pressure sensor switch was bad. Cleared it, drove it a little while longer until it came back. Got it replaced.

Not too long after, got another CEL, indicating the oil pressure was low, but not that the sensor was bad. Same deal. Cleared it, drove it a little while longer, and it came back. Got it replaced again, but went aftermarket this time. This didn't immediately fix it, as once again I got the CEL, but after clearing it, it stayed that way for quite some time. In fact, everything has been fine for the past four months including several wheeling trips and some long distance travel.

A couple weeks ago, the dreaded CEL returned with the low oil pressure code while gaining altitude up a mountain during a wheeling trip. This time, it's paired with another code indicating an issue with the oil pump. So, I get the oil pump replaced, take it up the same mountain to test, and the CEL returns with low oil pressure.

I am not burning oil, don't have any leaks anywhere (that I can see, at least), there's no debris, and I'm using the correct oil and oil filters for the Pentastar. Minus limp mode kicking in when the CEL appears and killing power, the Jeep drives fine. It makes no noise or behavior indicating it's starving for oil.

So I ask, after having all these parts replaced, what in the unholy hell is wrong with my oil pressure? I doubt there's actually a physical oil pressure problem, but I've replaced the sensors and pump. What else am I missing?


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post #2 of 17 Old 09-20-2017, 06:21 PM
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I have heard that the oil cooler unit (on top the engine where the oil filter is) has caused some issues.

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post #3 of 17 Old 09-21-2017, 03:10 PM Thread Starter
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Originally Posted by JTPhoto View Post
I have heard that the oil cooler unit (on top the engine where the oil filter is) has caused some issues.
It's just not consistent enough, that's the thing. When this all started, the original oil pressure sensor switch was definitely bad. The EVIC would show the PSI bounce between 0 and 99 and as it got worse, it eventually just stuck at 99 and the stored codes pointed to the sensor. It made sense.

When it was replaced, I was never bouncing between 0 and 99, but just getting sudden drops to 0. However, it'd jump back up to normal PSI, but at times it'd do it so fast that the oil light would blink and ding quickly, just like a bad wiring connection on any common electronic component. I never got the code the sensor was bad, but just that the oil pressure was low during those dips. And when it was replaced the second time with the aftermarket unit, it was the same deal but not nearly as frequent.

The only reason I swapped the oil pump was because I got the P06DD code, but I'm seriously wondering if the pump was ever bad.

I'm still thinking there's just a tiny little connection issue between the sensor and the plug/wiring that somehow kills the reading when the Jeep is bouncing around on a trail, like a pinched wire, bad ground, grease smear on a terminal... I'm gonna go in one last time and take another look, but I wanted to explore other possibilities before I go back and try examining the sensor again.

I can't find any articles or other threads on forums regarding this issue that wasn't resolved by a sensor and/or pump replacement.

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post #4 of 17 Old 09-21-2017, 07:22 PM
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To be safe I suggest to install an old school manual oil pressure gauge and monitor the pressure. That will tell you for sure whether or not it's the electronics or the beginning of a mechanical failure.

^^Jeff^^
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post #5 of 17 Old 09-22-2017, 10:22 AM
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As JTPhoto mentioned. you can't rely exclusively on electronics as there are too many interconnected elements that can malfunction. Connect a direct reading pressure gauge to discover if there really is a problem with the oiling system and, if there is, the extent of the problem.
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post #6 of 17 Old 09-22-2017, 02:43 PM Thread Starter
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Already on it with the manual oil pressure gauge, neatly sitting in the center console tray, and everything looks good so far. So, as expected, it doesn't appear to be a physical issue. However, I got another CEL today with an entirely new code, this time saying the oil pressure is too high. Which it totally isn't.

So, in going back to the beginning and addressing the first fix, the oil pressure sensor switch, I'm going to replace the wiring harness. It's not an expensive part and, like I'm surmising based on the behavior of the Jeep so far, should address any possible connection issues. Likewise, it's the only remaining component of the system in general that hasn't been replaced.

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post #7 of 17 Old 09-22-2017, 04:02 PM
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The PCM itself is part of that system. You may also have replaced a bad part with a bad part.

That's weird behavior to jump high or low. I would think a bad wire or short would pop one direction only (I'm guessing here).

Bad grounds can cause all manner of sensor malfunctions. Maybe check all your grounds, both at the battery terminal and on the firewall. Look for those braided grounds on your engine, and clean those connections too. It never hurts to have good clean grounds.

If you don't have a gauge to watch your voltage, get one. If your voltage is not consistent, that can throw sensors off.

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post #8 of 17 Old 09-22-2017, 05:05 PM Thread Starter
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Originally Posted by azzkicker View Post
That's weird behavior to jump high or low. I would think a bad wire or short would pop one direction only (I'm guessing here).
Yeah, the code today with the oil pressure high is an interesting twist, but I'm still thinking it's a wiring issue somewhere.

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post #9 of 17 Old 09-25-2017, 11:04 PM Thread Starter
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Alright. I've got the wiring harness replaced and so far, so good. The true test will be up in the mountains where the Jeep will get bounced and shaken around. However, I did notice on the old harness that one of the terminals on the plug for the oil pressure sensor was a little singed. It could be nothing or it could be everything, but I'll find out soon enough.

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post #10 of 17 Old 09-26-2017, 07:56 AM
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I believe that singe is everything. A carbon deposit from any arc (no matter how small still) leaves a altered resistance in the connection. This is why stress relief (and quality tooling) are so important. With vibration present even the weight of the wire can create enough force to (over time and cycles) loosen a crimp at the pin inside the harness plug.
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post #11 of 17 Old 09-26-2017, 08:24 PM Thread Starter
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I believe that singe is everything.
Welp, unfortunately it didn't fix the issue. So, I am now at a complete loss as to what the problem could be.

I've recorded a video of the instrument cluster as I was coming back down from my "testing mountain" again this morning. Same deal.


Here's another video of the dash, this time with my oil pressure pretty much steady at none. But as you can tell, the engine is just fine and obviously has oil pressure.


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post #12 of 17 Old 09-28-2017, 06:29 PM Thread Starter
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Alright. I've noticed a pattern.

The road conditions, causing the Jeep to bounce around are irrelevant.

Altitude is what is eventually killing the oil pressure reading. I'm still not actually losing oil pressure, so that's a good thing, but I'm now thinking the issue is with the computer itself.

At a certain altitude, the reading will start to die. It dips up and down. Eventually, as I get higher, the reading either drops to zero OR actually just sticks at a value, but doesn't change. It'll remain like this until I descend back down towards normal elevation. I did this test on normal and mountain roads in three different areas, all that climb a good 1000-2000ft from the base, and I got the same behavior each time.

I'm thinking temperature is a variable as well. I had this problem earlier in the year, when it was cooler, it went away during the late spring and summer months, and now that we're into fall and temps are dropping again, it's back. Likewise, a couple of my wheeling trips a couple months ago were actually at lower elevations than where I live which didn't cause any issues.

I'm still not entirely sure what to look for. It's entirely possible I just happen to have yet another bad oil pressure sensor switch, but that's a crazy coincidence considering I'm on my third one.

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post #13 of 17 Old 09-29-2017, 03:04 PM
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Has the PCM ever been reflashed? That MAY be something.

I'm stumped as well because PCM should not need to reference to atmospheric pressure to compare to oil PSi.... unless its part of the strategy in VVT calculations...

reflash and log data? - not cheap - I paid close to 200 bucks to have a Cadillac logged for three days hunting down an air pump issue, but we found it as he saw it go lean just as loop transitioned and right before the pump fail codes came up and traced that back to a very minor leaky vac hose (which only had vac when transitioning loops).

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post #14 of 17 Old 09-29-2017, 09:31 PM
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Just returned from a round trip to South Dakota in my wife's 2014 Jeep Grand Cherokee. Near Sante Fe, the CEL light came on so we went into the local Jeep dealership. They checked it out and the oil pressure sensor was bad. The mechanic told me they had a lot of these units going out and it needed to be replaced. It was replaced under warranty which my wife was happy about. My point: the pressure sensors don't seem to have a great deal of reliability since both dealerships I went to had a large stock of the sensors on hand. When you buy a replacement sensor, try to find a very high quality sensor or you'll be going through the same problem in the not too distant future. (BTW: my wife's Jeep just turned 26,000 miles, so it's not an age thing.) Good luck with resolving the issues.

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post #15 of 17 Old 09-30-2017, 04:34 PM Thread Starter
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Well, we figured it out. And by we I mean a mechanic NOT associated with a dealership.

The pin that powers the oil pressure sensor on the plug of the larger, external wiring harness to the left of the engine was loose. At first glance, even with a scan tool, everything looked fine, but after jiggling various wires around the engine, he noticed the voltage started fluctuating. He unplugged it and saw the pin was pushed so far into the plug that it almost looked like it wasn't there. He simply pulled it back through, plugged it back together, and had me take it up the mountain. That was it. No CEL going up or down. Finally.

So, even though the original sensor was bad, the internal wiring harness and the pump weren't necessary replacements (although I still can't explain the CEL and code for the pump). The warmer temperatures combined with the air pressure at the lower altitudes must have been just enough to keep power to the sensor. I'm a bit miffed that the dealership couldn't find this problem the half-dozen times they had it, but to be fair, it really came down to a process of elimination at this point.

Despite how much of a pain in the *** this entire ordeal has been, I'm glad it really just ended up being a crappy sensor and a loose wire. Sensors going bad is a part of modern vehicles, but I was really afraid I was going to have to get rid of the Jeep. My last two JKs had a litany of issues stemming from poor quality control that occurred well before the bumper-to-bumper warranty. This JK, on the other hand, has given me absolutely no trouble outside of this sensor issue.

Thank you all for posting your ideas and helping out.

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