Aisin "limp home" symptom in hot weather CONTINUED

[DonRam240]

See the archived 4th Gen forum thread "Aisin "limp home" symptom under load in hot weather" for reference. Again had similar EVIC messages towing/hauling camper in hot summer weather, like "4WD system unavailable". Do not remember having it stick in the 4th gear only limp home mode this year, although I'm not sure I waited before stopping and shutting down/restarting engine to correct it, so I could have missed that symptom this year. Just had dealer service done and they found code P0970 "stored". It had been cleared after the warranty repair on the transmission the previous year, so if I'm correct the stored code must have been recorded after the repair, presumably this past summer? That is the same code that was the pertinent one leading to the repair.
I asked them to check the wiring connector behind the wheel well liner, driver side front, that TransEngineer has said causes issues in some trucks with Aisin trans. They found no problem, mechanic saying, "do not see any issues at this time, pulled on wires, all solid at this time". I don't know if that reflects the level of inspection needed to find what we were looking for, didn't say he disconnected and checked for pushed-back pins/sockets, etc. I'm asking the service writer to ask the mechanic, will add more here if new information on the connector.
The Aisin's valve body was replaced, so barring a defective/failed replacement, it looks like there is another gremlin involved. Mech's advice was to pursue the new code if it is set again later. I think my basic generic code reader catches that code, so will scan SOON after any recurrence of the symptoms.

 

[DonRam240]

See the archived 4th Gen forum thread "Aisin "limp home" symptom under load in hot weather" for reference. Again had similar EVIC messages towing/hauling camper in hot summer weather, like "4WD system unavailable". Do not remember having it stick in the 4th gear only limp home mode this year, although I'm not sure I waited before stopping and shutting down/restarting engine to correct it, so I could have missed that symptom this year. Just had dealer service done and they found code P0970 "stored". It had been cleared after the warranty repair on the transmission the previous year, so if I'm correct the stored code must have been recorded after the repair, presumably this past summer? That is the same code that was the pertinent one leading to the repair.
I asked them to check the wiring connector behind the wheel well liner, driver side front, that TransEngineer has said causes issues in some trucks with Aisin trans. They found no problem, mechanic saying, "do not see any issues at this time, pulled on wires, all solid at this time". I don't know if that reflects the level of inspection needed to find what we were looking for, didn't say he disconnected and checked for pushed-back pins/sockets, etc. I'm asking the service writer to ask the mechanic, will add more here if new information on the connector.
The Aisin's valve body was replaced, so barring a defective/failed replacement, it looks like there is another gremlin involved. Mech's advice was to pursue the new code if it is set again later. I think my basic generic code reader catches that code, so will scan SOON after any recurrence of the symptoms.

Update: Connector was disconnected, pins inspected AOK.

 

[EZeis]

I assume the trans temp is getting too high? Was the trans thermal bypass valve replaced? It regulates the temp by regulating the flow to the cooler(s). They can stick.


Earl

 

[DonRam240]

I assume the trans temp is getting too high? Was the trans thermal bypass valve replaced? It regulates the temp by regulating the flow to the cooler(s). They can stick.


Earl

No, trans temp has always been good, usually 170-180 deg range under load. Have looked at that specifically multiple times in the loaded hot weather conditions that cause symptoms. From the 90+ degree day we got limp home mode and shut down for a half hour to cool after low speed uphill trip coming home, “trans temp started at 181 deg F, after shutdown rose to 185, then fell to 170 deg after a half hour.”
This is going to be some kind of electrical or electronic gremlin, I’m pretty sure, but locating it may take a couple more years of pulling codes when symptoms occur, asking dealer to investigate when it seems worth it, and head-scratching. Glad we bought the very best factory 8 year warranty extension! Other than this, which has become a minor nuisance since the valve body replacement, we love this truck.

 

[EZeis]

Ok I thought you had high trans temp from the past posts. Must of been a different thread.


Earl

 

[Tuesdak]

I am completely lost in what you are asking or just posting a fix? 180 for trans temp is high from what mine runs in Phoenix.

 

[Cummins12V98]

Highest temp I have ever seen was 179 locked in 2nd pulling a long 14% grade in 94 degree weather towing a combined 34k with my AISIN. Hopefully the new one does as well.

 

[DonRam240]

I am completely lost in what you are asking or just posting a fix? 180 for trans temp is high from what mine runs in Phoenix.

Two reasons for posting: to date have not heard from anyone else with the same issues for their 4th gen Aisin truck, so sharing in case others are in the same boat; and seeking suggestions if there are any. Hoping this will generate a service bulletin one of these days. It seems hard to imagine I’m the only customer with this Aisin-equipped Ram situation, but so far no one including TransEngineer seems to have seen the issues with an Aisin and any other owner. The fact that warranty replacement of valve body (and its misbehaving circuit board) seems to have cured the most serious aspect, being stuck cooling things off a half hour or more before limp home mode would go away, probably means something. Now seems much less problematic BUT the same EVIC error messages are happening under same conditions. Not sure if “never” will have limp home mode again, just have to watch. The fact it only happens in summer weather when hauling camper and towing race trailer limits my opportunities to see the symptoms. Do not expect anyone to have an easy answer, but if you don’t ask…..Love that 8 year warranty.
Thanks, guys

 

[Tuesdak]

@DonRam240 Ok so some of the problems were cured with a valve body. Nuff said about past problems as this is causing confusion.

What are the current problems, now? (Since that repair.) Are the temps still running 180F?

 

[DonRam240]

@DonRam240 Ok so some of the problems were cured with a valve body. Nuff said about past problems as this is causing confusion.

What are the current problems, now? (Since that repair.) Are the temps still running 180F?

As noted, same EVIC error messages are happening under same conditions, and not since hot weather hauling in summer. Trans temp typically in 170s. Stored code P0970 as noted above. Until next summer, do not expect to generate any new information.

 

[sag2]

Regardless of the fact that they said they checked the body connector under the drivers feet, if it were mine I would cut the T814 and T815 circuits close to the transmission and the TCM and replace the two circuits. Or at least wire around the connector at the very least. Easy to do, and free if you do it.

 

[DonRam240]

Regardless of the fact that they said they checked the body connector under the drivers feet, if it were mine I would cut the T814 and T815 circuits close to the transmission and the TCM and replace the two circuits. Or at least wire around the connector at the very least. Easy to do, and free if you do it.

Thank you for the suggestion. You’re well informed about those circuits and I’m definitely not. Could you please advise what those two conductors serve?

 

[transe]

I don't have circuit diagrams readily available, but since P0970 is an electrical fault, I'd say replacing the wires as suggested might be worth a try.
Or just wait until the fault / symptoms become more prevalent.

 

[DonRam240]

After some searching found this information and a 2014 wiring diagram related to the Aisin AS69-- that likely is the same for 2018.
Looks like the suggestion to bypass the connector for two circuits would be as follows, based on the trouble code description.
P0970 - Pressure control solenoid 3 control circuit low
That code should relate to these two circuits, correct?
T816 - Linear solenoid number 3 (-) Negative
T817 - Linear solenoid number 3 (+) Positive
Connections 4 and 5 in wiring diagram below (circuits T816 and T817 for Linear Solenoid #3) are at "Inline body/transmission 2" connector. Is that the 34-pin connector behind the driver front wheelwell that we have been discussing? Can't find that ID and location information so far. Looks like finding wiring schematics without a costly subscription to someone's data source is unlikely. If correct, I would look for the YL/BR and YL/PK wires running through that connector and solder a bypass wire around the connector for each of those, to try this theory.

 

[DonRam240]

Regardless of the fact that they said they checked the body connector under the drivers feet, if it were mine I would cut the T814 and T815 circuits close to the transmission and the TCM and replace the two circuits. Or at least wire around the connector at the very least. Easy to do, and free if you do it.

Please see today's post, thanks

 

[transe]

I don't have any diagrams, but it seems logical that that connector is likely the one behind the driver's wheelwell. Especially if it has wires with those color codes, next to each other, in the 4th and 5th positions from one end or the other.

 

[EZeis]

2018, no warranties left?? I wouldn't hack a harness if it's under warranty.

Earl

 

[DonRam240]

I don't have any diagrams, but it seems logical that that connector is likely the one behind the driver's wheelwell. Especially if it has wires with those color codes, next to each other, in the 4th and 5th positions from one end or the other.

Thanks. With due respect to Earl’s cautionary advice, may find connector, disconnect, clean thoroughly with CRC plastic safe Electronic Cleaner QD, apply fresh dielectric grease and reconnect. Can repeat the mechanic’s careful inspection of pins and their sockets.
Would like to know if it’s necessary to remove the inner fender liner to do this job, or if people have accessed that connector without that.
Then wait patiently to see what happens. With new Edge Insight CTS3 in place it is now easy to trigger a code reading on the fly while on the road if the EVIC error messages or the limp home symptom happens; it keeps collecting data until you tell it to stop reading. You just swipe down for the pulldown menu and touch the icon to trigger the process.
Soldering in bypass wires would be a last resort, if nothing else solves it and it is displaying nuisance limp home episodes with dealer unable to find a diagnosis and fix it. Still five years on our factory extended warranty