2009 JKU Randomly goes into Limp Mode - JeepForum.com
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post #1 of 5 Old 02-24-2017, 03:09 PM Thread Starter
ragerory
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2009 JKU Randomly goes into Limp Mode

Need some help on this. About a month before hitting 100k, my Jeep started to randomly go into Limp Mode. I do *a lot* of small trips (less than 3 miles) throughout the week. I've owned this Jeep for almost 4 years now, and I've never had any issues.

I took it to my mechanic and explained the issue. I've been using this mechanic for 5+ years now on other vehicles as well, and he's always been completely honest and fair to me.

He had checked the sensor, fluid, etc and said everything looked fine. He said he took apart the bar body (no idea what that is) and replaced some of the things in there (I'm not a mechanic, and cannot recall what it was that he replaced). The cost was about $550, I took it home, and all worked fine... for about 2 days. Then the problem came back. Again, it was intermittent. It did not happen each time I drove, but seemed to happen earlier in the day (taking my son to school, going to get coffee, etc), and not later on (going to pickup takeout or the like).

I brought it back to him and said the problem persisted. He gave me a loaner and called me back the next day, turned out one of the things he replaced was faulty. He took everything back apart, replaced it with the new part and off I went again (no charge here). He did tell me, though, that he had checked everything and if this didn't work I would have to go to the dealer because it could be some computer issue.

The engine code that came up was P0841 - Pressure Sensor - which he said was fine when they ran tests.

4 weeks later... Problem is back. Seems to be more frequent now. If I turn off the jeep and turn it back on, problem goes away. This seems to be a common occurrence from what I've been reading about these issues. Even more than that, now when it's *not* in limp mode, the transmission seems to adjust incorrectly, and my RPMs fluctuate just slightly enough to where it's noticeable and I can feel it...

I just took it on a 4hr drive down south on the Turnpike, and I had 0 issues. But back to city driving, it happens.

Now, I've read a few things about some software update or ECU thing that might be the cause of this? I'm not sure and would love some clarification on what that's all about - I can't seem to find anything online... I also heard from a guy in the local jeep club that '09's have bad transmission cover or something, and water can get into it? I'm not sure I am buying that because I can't seem to find any documentation to support it... I live in Orlando, FL and we get ****loads of rain every year, and this didn't start happening until recently (after 4 years of having it outside), so I'm not sure that can possibly be it...

Is there something I'm missing? It's blowing my mind and I simply can't afford to get a new transmission out of pocket. I'm not the original owner and I'm just over 100k miles (sitting at 103k now), so it doesn't look like I qualify for the powertrain warranty...

I love this Jeep with all my heart but I'm honestly thinking of saying f*ck it and trading it in because I've had to dump too much money into it lately between this, new radiator, brakes, tires, etc... I'm not a mechanic by any means but I'm fairly handy and can do some simple type things myself and am not scared to get my hands dirty.

PLEASE! WHAT'S WRONG WITH THIS THING!?

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post #2 of 5 Old 02-24-2017, 03:53 PM
ronjenx
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Is there another code present along with P0841? That's important to know for sure.

Did your mechanic do any electrical tests in the Low/Reverse pressure signal circuits?

Assuming your transmission is properly serviced...

Here is some info for the code you have?


P0841-Low,Reverse PRESSURE SWITCH RATIONALITY

Theory of Operation


The Transmission system uses three pressure switches to monitor the fluid pressure in the LR, 2/4, and OD elements. The pressure switches are continuously monitored for the correct states in each gear. If a set condition is identified, 1st gear and torque converter lock-up (EMCC) will be inhibited. The vehicle will launch in 2nd gear and shift normally through the gears without allowing EMCC. If during the same key start, the set condition is no longer valid, the transmission will return to normal operation (1st and EMCC available). Limp-in will not occur unless DTC P0841 is accompanied by a code P0706 and the MIL will illuminate after 5 minutes of substituted operation.

  • When Monitored: Whenever the engine is running.
  • Set Condition: The DTC is set if one of the pressure switches is open or closed at the wrong time in a given gear. If the problem is identified for 3 successive key starts, the transmission will go into limp-in mode and the MIL will turn on after 10 seconds of vehicle operation.

Possible Causes
RELATED TIPM TCM POWER CONTROL CIRCUIT DTCS PRESENT
LOSS OF PRIME DTC PRESENT
L/R PRESSURE SIGNAL CIRCUIT OPEN
L/R PRESSURE SIGNAL CIRCUIT SHORT TO GROUND
L/R PRESSURE SIGNAL CIRCUIT SHORT TO VOLTAGE
TRANSMISSION SOLENOID/PRESSURE SWITCH ASSEMBLY
POWERTRAIN CONTROL MODULE

2008 JKU Rubicon
42RLE Auto
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post #3 of 5 Old 02-28-2017, 07:41 AM Thread Starter
ragerory
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Yeah, I've seen that info before.

My mechanic had changed the Transmission Fluid Pressure Sensor.

So, I took it to Advanced Auto Parts today to get a reading as to what codes were. Below are the three that came up:

P1776 - Solenoid Switch Valve Latched In Left Rear Position
P0841 - Transmission Fluid Pressure Sensor / Switch A Circuit Range/Performance
P0731 - Gear 1 Incorrect Ratio

I called him this morning and told him the problem had come back and these were the readouts. He's looking into them, but did mention he doesn't believe they switched out the Solenoid Switch Valve, only the Pressure Sensor, so maybe that is it. He is looking into the codes and will call me back later.

I'm just really not wanting to go to the dealer on this.
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post #4 of 5 Old 02-28-2017, 08:37 AM
ronjenx
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Quote:
Originally Posted by ragerory View Post
Yeah, I've seen that info before.
Maybe it will benefit another reader.
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2008 JKU Rubicon
42RLE Auto
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post #5 of 5 Old 09-16-2021, 06:03 PM
Gerry112
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Any update to this? My Jeep currently has this issue. Need a solution.
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pressure regulator , tranny , transmission

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