Misc Code 6600
2006 Discovery 39J, MH300O, Cat 7. I have a mysterious problem.
My trans can work fine for awhile but will sometimes downshift from 6 to 5. If I put the trans into economy mode, it will shift back into 6. Tested a few things, while this problem is going on, the shift points in all gears will want me to drive to max shift point RPM's--@ 2250 or so. When I shift into economy mode, shift point lowers some,
1-2 about 1800
2-3 about 1800
3-4 about 2000
4-5 about 2000-2100
5-6 about 1800 or so.
I have it into two allison service centers and they can not find a cause and of course, when there, the trans was shifting fine. (also, one dealer installed a good working TCM but the trans still had the problem.) The two wires indicated to be checked both show good continuity so the intermittent problem continues. When working normal all shifts are accomplished between 1500-1750
Any thoughts, I was considering changing the throttle position switch to start with.