Hot weather Aisin limp home mode

[sag2]

This isn't rocket science, especially if the fault is there all the time. It is a circuit fault. It can only be one of two wires going from the TCM to the Solenoid in the transmission. They have replaced the TCM and the solenoid? That only leaves the wiring. So I'm back to replacing the terminals for the TCM side for the two circuits, then replace the same two wires from TCM to transmission connector. That only leaves the transmission pins, which can also be replaced with 68228245AA which is $337. There is no need to replace a complete harness. It usually results in collateral damage because the harness is put in as the truck is built, and can be very difficult to replace in the truck.

 

[Ozymandias]

This isn't rocket science, especially if the fault is there all the time. It is a circuit fault. It can only be one of two wires going from the TCM to the Solenoid in the transmission. They have replaced the TCM and the solenoid? That only leaves the wiring. So I'm back to replacing the terminals for the TCM side for the two circuits, then replace the same two wires from TCM to transmission connector. That only leaves the transmission pins, which can also be replaced with 68228245AA which is $337. There is no need to replace a complete harness. It usually results in collateral damage because the harness is put in as the truck is built, and can be very difficult to replace in the truck.

Is there a troubleshooting tree for this fault in the FSM?

From what I've seen googling around it can also have mechanical issues.

And as you say, the fault is now permanent, so a Mechanic with decent knowledge should be able to find it.

 

[DonRam240]

Agree with the argument for simplicity, and caution about harness replacement unintended side effects. I hope to learn about the sources of advice from Aisin and FCA in the case of the Texas owner, so as to understand the situation and resources the best I can before we launch the next try. If I knew our dealer had the best of diagnosticians as the tech for this I wouldn’t be so compulsive about the planning. Someone has to do an exhaustive job of detail work to get this right even if it’s limited to connector and/or wire and connection replacements. Not everyone works that way. Even on hourly pay, the patience and systematic thinking needed is not that easy to find. And there is no guarantee the dealer’s service manager will be fully on board for what is needed to get this right on the next try.
Thanks

 

[sag2]

Agree with the argument for simplicity, and caution about harness replacement unintended side effects. I hope to learn about the sources of advice from Aisin and FCA in the case of the Texas owner, so as to understand the situation and resources the best I can before we launch the next try. If I knew our dealer had the best of diagnosticians as the tech for this I wouldn’t be so compulsive about the planning. Someone has to do an exhaustive job of detail work to get this right even if it’s limited to connector and/or wire and connection replacements. Not everyone works that way. Even on hourly pay, the patience and systematic thinking needed is not that easy to find. And there is no guarantee the dealer’s service manager will be fully on board for what is needed to get this right on the next try.
Thanks

Sent you a PM

 

[DonRam240]

Thank you very much. Longer reply by PM. In one sense, this is “rocket science” even though it shouldn’t be.
Don

 

[DonRam240]

Update: Very positive conversation with service manager at Dick’s Wilsonville CDJR. Scheduled with his transmission specialist in 2 weeks. Understood that consultation with Ram or Aisin specialists may be needed, after we get the basic thorough diagnostic tree done. Cautiously optimistic. All the advice and support here much appreciated. At least the issue is now “fixed” and not intermittent.
Had to rent a U-Haul truck to haul the race trailer to Portland Int’l Raceway this past weekend. The Ram rides a lot better!

 

[DonRam240]

The diagnosis turned out to be one loose pin in that same connector behind the driver's front wheelwell liner, the connector that the dealership mechanic and my own mechanic friend had carefully checked and found no loose or displaced pins, previously. Do not know pin number. Repairing that pin cured the limp home mode as well as the cruise control. They are still working on a diagnosis for the simultaneous radio and EVIC blackouts (after two radio replacements, already).
So can we reasonably suggest that heat from that front tire, under load at highway speed in hot weather, may have expanded the plastic connector body more than the pin allowing the pin to slide, where it would not do so and somehow restore contact when cooler? Is there another heat source in that area? That is the side opposite from exhaust heat on the truck. And finally that pin moved more recently enough to remain disconnected so the limp home symptom, EVIC error messages, and P0970 DTC with MIL became fixed instead of intermittent? Does that stick together well enough to be reassuring that we've found the problem and there isn't another cause remaining that will cause intermittent symptoms to resume?