PRND321 underline issue

[ieetgluu]

A couple months back I noticed that my CTS was reporting the gear as Park while I was driving around. I then noticed there was no underline under Drive.
Park, reverse and neutral will always have the underline. Once I shift to drive the line will stay under N for a second then disappear all together. Truck will still drive, seemingly normal, but I've noticed if I shift out of drive to neutral then back to drive sometimes it does goofy stuff like seems to stay in neutral. This has only happened once or twice, but I don't typically shift like that.
CTS will report Park, reverse and neutral as does the underline, but then drive will be reported as Park.
Occasionally it has "cleared up" while driving. CTS will show correct gear and D will be underlined again. Although lately it doesn't clear up anymore lol

Symptoms seemed similar to those reported with NSBU switch. I replaced it and was of course amazed that the issue persisted. I don't usually care to shoot the parts cannon at something, but it seemed like a safe bet given the symptoms.

Trans built by Evan several years ago

Any ideas out there? Thanks guys for even reading. I've tried searching, never come up finding this exact issue.

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[ieetgluu]

Forgot to add, it has popped the p0700. I cleared it the first time, eventually it popped again and I've just left it. I've not yet been able to pull the actual code from it. I know, it would probably help here. My autocal will pull trans codes, right? It's been years since I've messed with that thing.

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[Ron Nielson]

It kind of sounds like TCM, but that's a wild guess. I suggest you call Evan. He's a very smart guy and likely the shortest path to the solution of your problem

 

[TheBac]

Until you know the actual code, you have no idea where to start. Do things in the proper diagnostic order. Get the code read first.

 

[2004LB7]

I'm going to guess, NSBU switch but codes from the TCM would be nice

 

[Bdsankey]

Without codes we're flying blind. I had a customer with a similar issue.

He changed to a brand new GM NSBU, no fix.
Changed his pigtail, no fix.

Then he called me to diag the truck and we had no communication with the after he put my new built trans in. Replaced the TCM with a known good used TCM and boom everything worked as it should.

Long story short, grab the codes and see what it tells you. It could be simple.

 

[ieetgluu]

Thanks guys. I do have another tcm that Evan had sent me years back. The one in it now bucks in the 3-4 shift under moderate to heavy throttle. The other tcm(I think he said it was from an 03) shifts beautiful but I lose elevated idle and o/d lockout which makes my tap shifter semi useless.

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[darkness]

Thanks guys. I do have another tcm that Evan had sent me years back. The one in it now bucks in the 3-4 shift under moderate to heavy throttle. The other tcm(I think he said it was from an 03) shifts beautiful but I lose elevated idle and o/d lockout which makes my tap shifter semi useless.

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It’s probably an 01/02 tcm but there are updated os’s that allow you to keep odlo with a separate switch and then use the cruise for elevated idle. Sounds like you have an lly?

 

[ieetgluu]

Yes sir, 04.5

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[ieetgluu]

P0708
Transmission Range Sensor “A” Circuit High


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[2004LB7]

P0708 Transmission Range Sensor A Circuit High

Might want to give an NSBU switch a try as it's a relatively easy and cheap fix if that's the issue

 

[1FastBrick]

P0708 Transmission Range Sensor A Circuit High

Might want to give an NSBU switch a try as it's a relatively easy and cheap fix if that's the issue

He tried that already.

"Symptoms seemed similar to those reported with NSBU switch. I replaced it and was of course amazed that the issue persisted. I don't usually care to shoot the parts cannon at something, but it seemed like a safe bet given the symptoms.

Trans built by Evan several years ago"

 

[2004LB7]

He tried that already.

"Symptoms seemed similar to those reported with NSBU switch. I replaced it and was of course amazed that the issue persisted. I don't usually care to shoot the parts cannon at something, but it seemed like a safe bet given the symptoms.

Trans built by Evan several years ago"

I missed that. Bad wire? Maybe installed it with the indexing wrong? Bad TCM?