Truck issue with codes

[Daniel6718]

So I've got a 2010 2500 chevy
Driving down the road it goes into limp mode

Has a
u0101
P0700
C0561
C0899

Prndl switch isn’t underlined

Clear code it drives fine through the gears till you slow down then limp mode again
Clear codes sometimes it won’t even move

I do some digging and batt good, alt charges 14.5
Tcm has 12v grounds and 5v reference going to the trans

So I figured the tcm is bad, replace it with one from Oreillys that wasn’t supposed to be programmed but turns out it already was, put it in the truck and same issue
But no codes now

Just the shift indicator is on the correct gear but the underscore flashes
Any help?

 

[Mike L.]

Possible ignition switch. Next would be a TCM.

 

[Daniel6718]

Ignition switch? As in it’s not sending power to the tcm? I checked that

 

[DAVe3283]

Ignition switch? As in it’s not sending power to the tcm? I checked that

The ignition switch might be sending less voltage than it should to the TCM, causing the TCM to behave oddly. They don't usually fail completely, you start getting weird stuff like this.


If the TCM from the parts store was already programmed, perhaps it was actually a used unit someone "returned" that might have a similar failure. You will need to try with a known good (or brand new) TCM.

 

[Mike L.]

New TCM is always best because it needs to be programmed to your truck.

 

[Daniel6718]

Ended up being the tcm

 

[Mike L.]

I figured that because of your 5V post. Allison works on 12V. Glad you fixed it.