cruise control and engine code

[maverick_935]

While travelling with my 32' fifth on and doing a moderate hill my truck downshifted hard again and set off the engine light.

I just replaced the NSBU switch and flushed the coolant , changed the filters.

Any thoughts on this or is there an update from GM that might help.

Only does it with the trailer on and hills. The trailer weighs about 11000-12000 lbs. Really not that heavy.

[DmaxMaverick]

Does it reset on its own, or do you have to stop and restart to resume normal driving? If it resets on its own, it's most likely an overboost fault, and there should be a corresponding DTC present. If you continue normal driving and the condition doesn't immediately repeat, the SES should reset quickly.

If you are able, at first, to pull a significant hill (4%+ grade) with that load, in OD, and you must stop/restart to continue normally, it's probably tranny/TC slip. You probably have a P0700 and other codes present. To prevent this, you'll have to remove the Edge, get out of cruise (let it downshift earlier), or disable OD as you begin the climb. A slip in direct (4th gear) is much less likely. If it is doing this in 4th (OD disabled), you have too much power for that load (and probably extreme EGT's, too). You only get so many slips before permanent damage occurs.

Otherwise, you'll have to read the DTC's to know more. I suggest attempting to repeat the conditions without the Edge connected. My guess is you won't be able to repeat it.

Also note:
When cruise is engaged, downshifts due to load demand (climbing a grade, etc.) are delayed for several seconds. This was a program modification to help prevent early downshifts (overactive throttle), such as would happen with an overpass or short incline. If you have a power mod (Edge), the power rise is much quicker than the expected speed increase, and you get too much power for that gear at that speed, and a slip can occur. The only options here are: Less power mod; Disengage cruise (allows earlier downshift when driving by foot); or, Disable OD and/or anticipate hills (depending on the grade and length of the hill).

[maverick_935]

I have to stop and shut down to reset 5th gear. When it kicks out I lose overdrive. This time after just one shut down the tranny worked normally. I was only running on edge level 1. The hill was not extreme or long. I stopped using cruise and it was fine including downshifts later this weekend.

[DmaxMaverick]

You'll have to read the codes to confirm, but it sounds like you were slipping OD. That load, a grade, and a little added power will do it. Driving without cruise allows for the earlier downshift, preventing the slip. Prevent this from happening, or you'll find it "limps" easier with each occurrence. If allowed to continue, a tranny overhaul will be required. Eventually, with repeated slipping, it will no longer be able to hold OD under moderate conditions with stock power.

[Kennedy]

Try it without the Juice once. This may sound odd, but we can typically make and apply more power with a good tune and not slip the trans than what you can do with a harness box and it's "supposed" slip protection.

[maverick_935]

Do you mean remove the eddge or just put it on stock and try it?

[Kennedy]

Remove it and try without it.