[Brews]

Hey, i have a Chrysler sebring 08 with 6.2k miles.
While casually driving the check engine light got lit and it went into limping home mode.
The error code recovered was p0734 but where i live in sweden there is no mechanic that has experience with chrysler. They tried flushing the transmission but that did nothing.
The old oil was clean though.
A couple of Google searches has told me p0734 = 4th gear incorrect ratio, so i talked to a transmission shop and he told me without looking at the car 'the shaft is broken, needs a full rebuild.' To which he quoted me a $5000 cost.
I've read about changing the transmission shift solenoid pack, outgoing and ingoing sensors for the transmission.
Are these possible solutions or is it most likely an internal problem which would require a rebuild?

 

[ImperialCrown]

Welcome to the forums.
One cannot diagnose the car unseen. Always diagnose first. Don't guess at this.
4th gear ratio errors can be due to OD clutch slip or broken hardware.
P0734 Chrysler - Gear Ratio Error In Fourth Gear (at https://www.autocodes.com/p0734_chrysler.html )
Is there a P1790-fault immediately after shift fault also?
https://autoservicecosts.com/obd2-codes/p1790/

 

[Brews]

The only fault detected is p0734. After resetting the codes it shows up immediately on starting the engine - still in park.

 

[AllanC]

. . . The only fault detected is p0734. After resetting the codes it shows up immediately on starting the engine - still in park. . . .

This is very strange behavior. The transmission controller constantly calculates the ratio between the speed of the input shaft to the output shaft (before final drive differential) and compares to the known or expected value of each forward gear ratio. But this implies that the vehicle must be moving. When the vehicle transmission is in PARK, the input shaft is turning because it is not attached to any output gear set. The output shaft is not turning since the vehicle is stationary. There is no calculation and comparison done on gear ratio with the vehicle not moving.

I am thinking there is a wiring problem with the input and output speed sensors or the transmission controller portion of the PCM / powertrain control module has developed an issue. But if there were wiring circuit problems with the input and / or output speed sensors, other codes would be set indicating wiring problems.

 

[AllanC]

. . . . The only fault detected is p0734. After resetting the codes it shows up immediately on starting the engine - still in park.. . . .

How are you clearing code P0734 from PCM memory? Disconnecting the battery for a few seconds will NOT erase the code. You need a scan tool to clear diagnostic codes.

 

[Panterasr9]

How are you clearing code P0734 from PCM memory? Disconnecting the battery for a few seconds will NOT erase the code. You need a scan tool to clear diagnostic codes.

I agree here get a good scanner like an Autel and specifically scan and clear the TCM. See what comes back.

 

[Brews]

I'll call the shop tomorrow morning and get some more info but I believe they'd use a good scanner (but who knows).

 

[Brews]

Hello. First off I want to apologize for the delay. Shop closed for vacation - and I also went on vacation a week after that.

I have got the car back. The car only switches to Limp home mode AFTER I try to switch to 4th gear. When this happens I also hear some bad sounds from the transmission. When I shut off the engine shortly after trying 4th gear I can hear something spinning in there for about 10-20 seconds (can't remember this happening before).

Cant get a hold of a scanner right now, will try to order one at the end of the month.

 

[AllanC]

. . . The car only switches to Limp home mode AFTER I try to switch to 4th gear. When this happens I also hear some bad sounds from the transmission. . . .

Review my post #4 dated July 14, 2020. If the vehicle is NOT moving then there are no pulses generated by the input and output speed sensors to determine by calculation that there is an incorrect gear ratio. So this has to be an electrical fault / erroneous signal sent to the transmission control logic that is causing a misleading code to be set. Attached image shows the wiring between the PCM and transmission controller. Check for frayed wires, shorts, corroded connectors, loose fitting pins to mating receptacles.



In 4th gear, the OD and 2/4 clutches are used so I would inspect wiring associated with these clutches and the associated pressure switches.

. . . When I shut off the engine shortly after trying 4th gear I can hear something spinning in there for about 10-20 seconds (can't remember this happening before). . . .

Is your vehicle equipped with the 2.4 liter 4 cylinder engine? If YES then the spinning noise could be the alternator decoupler pulley allowing the alternator rotor to spin down at its own pace after engine shut off. This is not associated with the transmission.

 

[valiant67]

When I had troubles only shifting to 4th gear in my Voyager, the transmission was toast. The shift to 4th would fail and then put the transmission in limp mode. As long as I kept OD off, the van was fine and ran through 1-3 normally.