Quote:
Originally Posted by bjm
Went to my dealer this morning(200k round trip,so far 800ks for 4 flashes) for this problem!!!)Brought up a code 104 which is a faulty actuator to be replaced FOC ,this is the good news,the bad news was that there were 100s on backorder world wide,so he said!!!So waiting again.I thought from US forums I have been on the N23 problem stems from a faulty board(from new )in the TCM and the flash was FCs attempt to not have to replace the TCM on recall.If this is the case if a faulty TCN code appears FC should have to replace FOC also.Has anybody put the pressure on them for a new TCM?
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I think "TCM" is being used wrongly a little bit.
Jeep (the service manual.) uses "TCM" to refer to the "transmission control module"; which in the V8s is part of the PCM (powertrain control module.), and in the petrol V6 is a separate module. I don't know about the CRD (not in my service manual.), but I'm sure it's different again.
So IMO it's unlikely that the real problem is a fault in the TCM, since it's different in each engine.
The TCM also isn't involved with the transfer-case or 4WD system (the 2WD GCs use the same TCM.).
The transfer-case, QDII solenoids, etc are controlled by the FDCM (final drive control module.).
The transfer case is shifted between hi/neutral/low by the "shift motor" (as the service manual calls it.), which most people call the actuator.
Really just a normal DC motor with some reduction gears driving a cam.
The position of the transfer-case (hi/neutral/low) is measured by the "mode sensor", which is essentially part of the shift motor. According to the service manual it's just a 1.4K +/- 20% potentiometer and 1K +/- 20% wiper resistor.
I've seem some folk on the US forums refer to the shift motor as the transfer-case motor or TCM, which is a bit confusing.
IMO the most-likely candidate to be faulty, is the "mode sensor" (just by nature of what it is.), giving an incorrect resistance making the FDCM think the motor shaft is in a position which it is not - And as a result shifting into neutral while trying to correct the position.
Remember it's a safety recall; the danger being an unexpected shift into neutral causing the car to roll away, or maybe loss of control while driving/4wd'ing.
They're only required to address the safety issue; which they appear to have addressed by making the FDCM logic more 'strict' - Reducing (hopefully eliminating.) the chance of it shifting to neutral, but also reducing the tolerance for shifting into low-range too.
I'm guessing that there's another legal requirement; where if a safety recall causes a secondary cost (in our case, the cost of replacing the actuator which was previously being 'tolerated' by the old FDCM firmware.), that cost must also be covered.
If the actuator/shift motor just had a fault which couldn't be considered as a safety issue, it probably wouldn't have been a recall in the first place... just our bad luck
I wouldn't mind getting hold of a shift motor, and seeing how hard it is to service or replace just the sensor.
IMO if it really is a potentiometer, it's inevitable that it's resistance will change over time as it's bound to corrode. Just a good clean & condition with dielectric grease might be all that's needed.
For what it's worth, here's my logic atm...
IF the issue is caused by the resistance measured by the FDCM 'shifting' out of spec, the firmware update to the FDCM might only be relevant to the current norm. As-in, maybe shift motors which are reporting slightly incorrectly are handled correctly by the software update. Where-as shift motors which are reporting more-incorrectly result in the "service 4wd system" error.
So if you think about it logically (and assume all of the above is true.), everyone's shift motors will eventually "fail".
The earlier you get the recall done, the more chance you have of not getting the shift motor replaced on recall (if yours is still "OK".) - Possibly to have it fail later.
The longer you wait, the more chance you have of having the shift motor replaced during the recall - Since it's more likely to be too far out of range by that time.
So I'll be waiting until the recall ends (dunno if that's even possible?) or I start getting symptoms.