2005 TJ Slips Out Of Gear

[Pear]

My '05 TJ started slipping out of gear. It's an automatic. She has 130,000 miles.

She's going through a wear cycle and has many codes:
-----
P0871 - Overdrive hydraulic pressure switch circuit.
P2096 - Downstream post catalyst fuel trim system 1 lean. (TSB?)
P2098 - Downstream post catalyst fuel trim system 2 lean. (TSB?)
P0700 - Transmission malfunction present.
P0871 - Transmission fluid pressure sensor / switch C circuit range / Performance (pending).
-----

I was working on 2096/2098 when the transmission slippage began.

I changed the transmission fluid and filter, but there's no change.

Maybe it's a common problem? I'm hoping someone here can assist by cluing me in on what to check etc.. I have fairly limited tools.

I prefer to start with the simplest things first.. For instance, could it be a hole in a vacuum line or a loose sensor connection? I just don't know where to start looking!

 

[JPNinPA]

First check your battery. Bad battery can throw many erroneous codes.

Did you use the correct fluid and enough?


Never look down on anyone unless you are helping them up - Jesse Jackson

 

[JPNinPA]

Symptoms

Symptoms of a P0871 include:

Transmission overheating
Slipping
Failed gear engagement
Causes

Low transmission fluid level
Dirty transmission fluid
Transmission fluid leak
Overheated transmission
Overheated engine
Damaged wiring and connectors
Transmission pump failure
Transmission fluid pressure sensor failure
Transmission fluid temperature sensor failure
Transmission control module failure
Internal mechanical failure
How to Diagnose the Code?

One of the first steps to diagnosing a P0871 OBDII trouble code, is to check the manufacturer’s TSB database to see if there are any known solutions for this transmission problem. Next, the wiring and connectors leading to the TFPS sensor need to be inspected for signs of damage and corrosion. The transmission fluid pressure sensor will need to be tested as well, to determine if it is operating properly. If no issues are found up to this point, then an internal mechanical issue (most likely in the valve body) should be suspected.


Never look down on anyone unless you are helping them up - Jesse Jackson

 

[Pear]

The battery has been replaced with the error present before and after.

A shop did the fluid and filter change. I checked it using the correct procedure then, and I'm going to check it tomorrow too. I've read several posts of people slightly overfilling their ATF, so I was thinking of adding some this weekend (maybe).

The fuses and relays all look good.

In looking at the P0871, there's a TSB for it talkin' 'bout the connector getting corroded. I'm going to try to look at that tomorrow to see if I can get to it. I don't have the tools or jacks to lower the transfer case skid, so I may not be able to see it.

Here is the TSB, although I don't know if it's the problem or not..
21-009-05.pdf

Other sites say damage and corrosion are common for this harness. Where Jeep recommends cutting back the wire and replacing the connector, others say that it can be cleaned. The issue is that I may not be able to get to it..


Would there be any other things to check?

 

[JPNinPA]

The battery has been replaced with the error present before and after.

A shop did the fluid and filter change. I checked it using the correct procedure then, and I'm going to check it tomorrow too. I've read several posts of people slightly overfilling their ATF, so I was thinking of adding some this weekend (maybe).

The fuses and relays all look good.

In looking at the P0871, there's a TSB for it talkin' 'bout the connector getting corroded. I'm going to try to look at that tomorrow to see if I can get to it. I don't have the tools or jacks to lower the transfer case skid, so I may not be able to see it.

Here is the TSB, although I don't know if it's the problem or not..
21-009-05.pdf

Other sites say damage and corrosion are common for this harness. Where Jeep recommends cutting back the wire and replacing the connector, others say that it can be cleaned. The issue is that I may not be able to get to it..


Would there be any other things to check?

What do you mean "look good"? When assessing fuses and relays.

In the TSB the only Symptom is the code. At a minimum the wiring can cause issue. The inspection seems simple enough. Look for corrosion.
Though without tools this may present an issue.


There is a note in the TSB that this may be reimbursable under warranty. So you might a
Call jeep and check if they will repair under that warranty.

Regards,
JPNinPA

Never look down on anybody unless you're helping them up. -Jesse Jackson

 

[Pear]

What do you mean "look good"? When assessing fuses and relays.

While looking for a TSB on P0871 as the article you mentioned suggested, I found this info about checking the wiring starting with the transmission fuses and relays (at the bottom of this post).
P0871 Error Code | Jeep Wrangler TJ Forum
What I mean by "look good" is that fuses weren't busted and the relays had clean connections.

In the TSB the only Symptom is the code. At a minimum the wiring can cause issue. The inspection seems simple enough. Look for corrosion.
Though without tools this may present an issue.

That's what I'm doing now.

There is a note in the TSB that this may be reimbursable under warranty. So you might a
Call jeep and check if they will repair under that warranty.

I'm the second owner and she's 16 years old (I've had her 12 of those years ). I didn't think they covered stuff under warranty that far out and for a second owner.


Edit to add:
I checked to see if I could get to the connector from under the Jeep and I can't (tsb mentions lowering the transmission by up to 4" to get to it). Not sure what to check next.

 

[mark sr]

I didn't think they covered stuff under warranty that far out and for a second owner.

24 yrs ago I bought a 7 yr old jeep cherokee. I had it about 6 months and there was a brake rotor recall at which time the service dept found an unrepaired transmission cable recall which they also did - all free of charge. While some recalls have time limits, it's always worth checking into.
​

 

[JPNinPA]

Ok the fuses are good. Besides visual some use a multimeter. You could check for voltage on both sides or continuity.

The relay you might try swapping it with another. Id have to check if they are the same but swapping with the horn will give quick feed back.


As mark sr noted some TSBs are safety related (recall) and have no expiration.

Never look down on anyone unless you are helping them up - Jesse Jackson

 

[Pear]

The relay you might try swapping it with another. Id have to check if they are the same but swapping with the horn will give quick feed back.

That's a neat hack, I'll have to remember that!

..which they also did - all free of charge. While some recalls have time limits, it's always worth checking into.

..some TSBs are safety related (recall) and have no expiration.

I see, I didn't know that. I'll have to check with them!

I reset the brain somewhat recently, so the check engine light isn't lit. I'm assuming I'd need to drive it a bit to regenerate the codes before I take it in?

 

[JPNinPA]

Yes or the codes are not real.

I cannot express enough how a bad battery or connection can cause many odd issues and codes.

The battery wires themselves can be corroded. The connectors and the connection locations The ground from battery to engine or battery to chassis needs to be less than 2 ohms or you will see issues. The contact areas clean along with the connectors.
Look at these things annually.

Get the battery load tested.occasionally.


Never look down on anyone unless you are helping them up - Jesse Jackson

 

[Pear]

I cannot express enough how a bad battery or connection can cause many odd issues and codes.

Well, the battery was giving me problems not long ago. The 02 sensor ODB codes existed at that time, but not the slipping out of gear codes.

It was acting like it wouldn't charge. I replaced the battery. I also replaced the PCM (didn't fix, so returned it) and the alternator. Like I said, it's going through a wear cycle so all kinds of stuff has been going wrong all at once (fuel pump, water pump etc)..

I'm not 100% sure the new battery and alternator solved the charging problem. After the slipping out of gear issue, I haven't been driving it. I keep the battery fully charged with a battery maintainer but I don't know if it's charging while driving.


..I'd love to look into the battery connections. I have a multimeter. I'm not sure what I'd be looking at though. Can you explain what connections to check or point me to a website with step by step instructions / pictures?

 

[JPNinPA]

Ill look for a website or video.
Start with the ground lead. Is the battery post corroated? Polish it to a shine. Same with the ground connector. Inspect the wires from the cable into the terminal connector. Do they look corroded, fragile or broken? If so replace the cable. Follow the ground cable. It splits to the engine and chassis. At the engine disconnect and clean and lightly sand to a shine both the engine and wire end. Reconnect and tighten. Do the same for the chassis side.
Inspect the wires at those ends.

Then do the same for the positive side.


Never look down on anyone unless you are helping them up - Jesse Jackson

 

[Pear]

Ok - I'll try that. This weekend is busy, so it may be a minute.. Thanks for your help btw.

Will this inspection require disconnecting the battery? If so, will that reset the error codes I'm trying to capture?

 

[JPNinPA]

Yep
But if that is the cause. It will be worth it.

Never look down on anyone unless you are helping them up - Jesse Jackson

 

[superj]

and if its not, they will come back after a while

 

[Pear]

Updating the thread..

The battery cables looked good in a cursory check.

The ATF was low when I checked again, it was full before so I must have a leak. I can't find the leak, so it could be blow-back and not leaving a trace.

I'm going to check with a shop on the issues from here, thanks again to all for helping!

 

[JPNinPA]

Inspect for leaks from the bottom the radiator back to the yolk. Any thin oily fluid is suspect. What color is your transmission fluid?

There is always a trace. Just have to find it.


Never look down on anyone unless you are helping them up - Jesse Jackson

 

[superj]

At least you know why it's slipping. Now is the riding part and you will be good again. At least you know it's not the transmission