The error code wheel of fortune continues - This time P1242

[JoergM]

Originally Posted by JeanLuke

A random thought this morning...
The TCM has had bared wires flapping about in the loom. It is possible that one of the output transistors has been damaged, or one of the new splices is dodgy (not a criticism of workmanship but a logical place to look).

Sent from my moto g( plus using Tapatalk

Well, I would not cross anything out tbh. I doubt that the shrink tubes are causing any trouble. I have taken the harness out again, after I thought I missed a part as mentioned on the picture. I made sure all the bare wire are somehow covered with something so that they cannot touch each other. And I checked each wire with a multi meter, if there is actually some flow from one side to the other. All wires showed no sign of damage.

Having the wires exposed could of course fried one of the other electronic parts. The question then is: which one? Not sure how I ever could check his and even then how and how can I get access to it. Could be somewhere in the TCM or even worse, on the cuircut board where the plug goes in which is, what I heard pretty expensive and I guess hart to get access.
This would also make sense since the issues keep coming and going randomly. I took the Jeep for another quick drive this morning. No issues, the transmission worked perfectly.

[JoergM]

Originally Posted by RTB

Good to know.

Thats a good find. Thanks for sharing.

[RTB]

The thanks as usual goes to AdrianD. It is page 10 of the document he attached to his post earlier today.

These lads seem to have some good stuff tucked away.

[JoergM]

I just took the Jeep to town again. I paid specifically attention to the starting procedure. When turning the key I was waiting till all lights on the dashboard went off and the init cycle had passed and only then started the engine.

I did this 4 times during the time and at this stage, no problem with the transmission. I am not sure if this is sheer coincidence or if this is really what might cause the transmission to act up. I will certainly monitor this over the next couple of days and I have to take the Jeep for a longer stroll than just 15km back and forth.

[JeanLuke]

That's a little random. I've not seen that before. The TCM is prone to play up if the battery voltage is low. Perhaps the firing of the glow plugs simultaneous with cranking (pure guessing)?

Low hanging fruit:
Check the battery voltage - particularly during glowing and cranking
Check the transmission oil level
Clear the TCM adaptives and reset, considering what has happened to it. WJ Diag is your friend here.

[Adrian D]

Didn't you mention that you used a smaller battery from the V8?

I recently installed an Exide 95Ah AGM (850CCA) and it spins the engine very fast compared to the old, tired 100Ah battery (same 850CCA)

[JoergM]

Originally Posted by Adrian D

Didn't you mention that you used a smaller battery from the V8?

I recently installed an Exide 95Ah AGM (850CCA) and it spins the engine very fast compared to the old, tired 100Ah battery (same 850CCA)

I have installed the V8 battery on my wife's car. It has only 650 CCA. I had to do it since her battery died. I got a replacement due to warranty and the new battery has either 850 or 950 CCA. And that's the one I have installed right now. So I guess the battery should be fine. The V8 is good enough for her car.