Limp Mode! OD Pressure Switch Rationality Fault - Need Help

[Pear]

We have an '05 Wranger X, automatic (42RLE).

I started having strange issues that finally came to a head.. The MILF light came on, then my speedometer went wonky, then gas mileage dropped, then she stayed stuck in 1st gear (limp mode).

This doesn't have to do with the shifter linkage (fixed that long ago lol).

I get the following codes:

P0871 - Transmission.​
P0700 - General Code: "There's a transmission problem."​
P0153 - O2 Sensor​
P0133 - O2 Sensor​
​

P0871 = "OD Pressure Switch Rationality Fault"

While researching I found some stuff about the P0871 code that listed the problems I have.

..Which brought me to a service bulletin:
autocodes.com/uploads/chrysler/21-009-05.pdf​

..Which calls for:
Wiring 10-way Pigtail Harness​
Solenoid/Pressure Switch Assembly​

Dealership service dept is quoting about $700 (parts+labor), which I wont have anytime soon.

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Has anyone had this issue before and know of a fix?

For instance they're saying moisture gets into the wiring housing and corrodes the connectors - can those be scraped (scratched) to make a clean connection?

If I bought the parts, how hard would it be to replace myself?

Can a generic harness or solenoid be used - or can either be serviced?

Could the issue be something else all together? ..For instance could something else be wonky and be causing an incorrect error code - like my transmission fluid is bad or something?

..Thanks in advance for any help!!

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Update: I looked up the error on YouTube and saw a lot of folks replacing the sensor that goes into the transmission - about $60 bucks - could it be something as simple as this? I looked it up on our TV which doesn't allow me to do a "deep search" so the results I got were for Dodge trucks and the like (same transmission). I'll keep searching..


If it's just that sensor, has anyone replaced that on a TJ?


I'm new to this forum - have heard great things! Thanks for any help!!

 

[JPNinPA]

First start with the cheap n easy.
Test your battery and clean all the grounds. Both sides.
Inspect the wiring. Esp where the engine trans meets the firewall.
Start with unplugging cleaning contacts and replugging the solenoids on the trans in.


Regards,
JPNinPA

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[JPNinPA]

Check trans fluid level.
Consider flushing and changing any transmission filter.


Regards,
JPNinPA

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[Pear]

Tested battery and alternator - the alternator may be week, averages between 13.8 and 14.2 with everything on... Could that be related?

That shouldn't make the speedometer act crazy should it?
I honestly don't know.

Battery comes in at 12.6. Oddly it came up as 60% after 2 days sitting, which made me think the alternator was at fault from when I has driven it before, that's why I tested the alternator...

But I didn't think either of those things would be related to the P0871.

I can look at trans connections tomorrow - but it's all Greek to me (I know how to replace the speedo gear, but that's it). I'm not confident I'll know what I'm looking at.



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[JPNinPA]

A bad battery or poor connections can cause a number of issues including false CEL.

A bad alternator will not recharge the battery properly.
Battery 12.6v off 14.4v on.
Load test battery and alternator.
Correct these issues first. Then be sure the wiring to the battery is good. Lightly sand the inside connectors and the opposite ends. The wires themselves can corrode and cause issues.
Ill see if i could find pics or videos.


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[Pear]

Please see above your response, where I state the battery is 12.6 and alternator is 14.2 with everything on.


...What's the next thing to check?

 

[JPNinPA]

Not sure what you mean by it came up 60%. If load testing 60% of cca then you have a bad battery.



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[Pear]

The battery was 60% full (charged) after sitting for several days. It's a newer battery. I charged it. It's full.



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[JPNinPA]

Note the pressure relay marked. Check the wiring.


O2 sensors don't usually go bad for the same reason without some other common cause. Like an exhaust leak above the top O2s like in the manifold at the engine. Bad PCM or bad connections.


Regards,
JPNinPA

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[Pear]

Got the garage cleaned out and swept today, so I'll be crawling under there soon... (My back hurts from moving all that stuff, so I may give it a few days.)

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