Low Sump Temperature

[Duffer51]

I have a 2004 Dynasty with the Cummins ISL400 and Allison 4000MH Transmission.  When starting the coach I get a "warning" light which indicates "an out of range condition exists within the engine protection circuits. Stop coach, check al fluid levels.  When checking the transmission fluid level using the Transmission Control I have a code that indicates Low Sump Temperature.  The temp gauge after running the coach for a while shows the transmission temperature just over 140.  I've tried sticking the level with the dipstick, but apparently there isn't one, at least that I can find.  The coach has 44,000 miles on it and the transmission was flushed etc 6 years ago.  I don't know whether to add some fluid or if it's a bad sensor or what.  Any suggestions would be greatly appreciated.  TIA

[vito.a]

This sounds like possibly two separate issues.  The warning light may not be associated with the transmission.  Have you checked for engine codes with a heavy diesel code reader?  It connects to the engine ECU at the port under the dash next to the drivers' feet.  

The transmission dip stick is probably accessed from inside the coach.  There should be a removable hatch in the bedroom.  It should be warmed up when checking and that means driving at least a short distance.   However, unless something is wrong with the sensors the control pad check takes precedence (but again, it must be warmed up).  

[96 EVO]

Take it for a run, then check trans level with the keypad.

[Duffer51]

The Owners Manual states to check fluid levels so that's what I've done.  The transmission is accessed thru the door in bedroom closet but there's no dipstick. 

[Ivan K]

The transmission fluid must be over 160 degrees for the hot test to run. If you don't want to drive the coach, stand on brake, put it in drive and give it some more RPM. The converter will warm it up pretty quick. Even if you had dipstick, it is just an informative measure to know its safe to start the transmission and do a hot check. But like Vito said, I doubt this is a reason for your warning light.

[OhReally]

Ivan is correct. Because the transmission control check tries to be an accurate representation of the expanded (hot) fluid level it does not work unless enough transmission heat exists.

This doesn't rule out a problem with the transmission fluid level sensor but the temperature is something to check before panicking. Just give it a check when you know the transmission should be hot, like under driving conditions when you've just climbed a hill and it's not raining. Rain cools the transmission quickly.

 

[jacwjames]

FWIW,

I have a dipstick on the side of the transmission, I can check oil from underneath and/or through the bedroom floor hatch, and/or the keypad. 

 

Do you have any reason to believe you are low on oil, any apparent leaks or problems since the last time you drove the coach?

[JohnC3]

Just a thought and I am not tranny guy, but could low sump temp be an alert that the tranny temp is to low to do a hot check?

[ktloah]

When your transmission temp is in the normal operating range, check your transmission fluid using your control pad. My 04 dynasty has no dipstick and this is how to check it. Are you sure you have the 4000 series trans? I  the same coach and the ISL 400 is mated with the 3000 series...

[Gary Cole]

Looks like there is a low sump temp code as mentioned in the post. Indicates that the temp sensor is out of low range indicating a faulty sensor. Nothing to do with fluid level 

Edited April 29, 2023 by Gary Cole

[Duffer51]

Thanks for the feedback.  The transmission is in fact the Allison 3000MH, not the 4000MH, if that makes any difference.  Given that the owners manual states to check fluid levels with this warning light, that's what I was doing when the Low Sump Temperature code was displayed on the keypad.  The Transmission Temperature gauge thus far reads within range that I've always had of around 160 degrees. All of the other fluids I've check are ok so I'm assuming it's something with the sensor and will drive home and have it checked out. 

[vanwill52]

On 4/29/2023 at 1:49 PM, Ivan K said:

The transmission fluid must be over 160 degrees for the hot test to run. If you don't want to drive the coach, stand on brake, put it in drive and give it some more RPM. The converter will warm it up pretty quick. Even if you had dipstick, it is just an informative measure to know its safe to start the transmission and do a hot check. But like Vito said, I doubt this is a reason for your warning light.

I once suggested the same OBVIOUS thing to raise trans temp enough to get a reading on the Allison keypad.  Someone chimed in, "I don't think I would want to subject the trans to that kind of abuse".  I referred them to the Allison Service Manual, under the heading "FULL THROTTLE TEST", where the FACTORY MANUAL says to check for slipping clutches by applying WOT while in DRIVE and holding the service brakes.  So, I hardly think applying MODEST throttle while holding the service brakes is an "abuse".  Do so, and as Ivan said, the trans temp will rise very quickly, allowing you to do the Allison keypad test.  Even on a forum like this one, where Bill D absolutely required technical literature backup or PERSONAL EXPERIENCE, there are still folks posting OPINIONS, rather than FACTS.

A similar situation comes to mind in regard to operating the engine for a short period and not letting it come to full operating temperature before shutting down.  For those of you that think Cummins meant you could NEVER operate the engine without allowing it to come to full operating temperature, let me assure you that my coach, with over 200,000 miles on the engine, will be cranked up and running for a few minutes EVERY time I move it out of the shed to wash it.  Am I going to take a long drive before washing it?  Short answer--"NO"...Long answer--"HELL, NO".  "Someone" read something a Cummins manual stated, saying that "FREQUENT and REPEATED instances of running the engine for short periods will shorten engine life".  It DID NOT say you had to take a 20-minute drive every time you cranked the engine, or your engine will crap out.

And anal attention to tire pressure, based ONLY on an accurate individual tire weighing...don't get me started.  No one pays more attention to tire life than trucking companies.  How do you think THEY handle tire pressures?  Guess!!!

End of rant.  Thanks for your patience.