New build with issues

C

Chilly

Member
Dec 4, 2018
101
3
18
Recently finished up a large engine and transmission overhaul on a 6 speed LBZ.
Last night fired everything up but have a small list of transmission codes. Dash is reading shift range inhibited along with these codes.

- P0751: Shift solenoid A performance or stuck off
- P0756: Shift solenoid B performance or stuck off
- P0659: Actuator supply voltage circuit high
- P0843: Transmission fluid pressure sensor switch A circuit high
- P0877: Transmission fluid pressure sensor switch D circuit low

Truck only has 14Liters of oil and is just on the bottom of the dipstick (OEM deep pan), although nothing was open last night to go get more oil.
Truck is not moving at all. All solenoids were replaced along with the pressure switch manifold. I did not however replace the internal NSBU switch.
Pump got Mike L's orange spring to bump up pump pressure along with his shift springs and TransGo kit.
Kit is Suncoast GMAX-CAT4 kit and I triple checked all measurements for clutches.

I did have some problems initially with the A Trim spool sticking from the TransGo shift kit. I ran super soft sandpaper over a small tube I had laying around and spin it buy hand in the bore. Everything moved smooth after that. I double checked to not mix up A and B trim solenoids as one is normally open and the other normally closed.

Looking for suggestions...

1.) NSBU switch bad?
2.) A or B trim valve stuck?
3.) Codes related to low oil level?

Thanks
 
Last edited:
C

Chilly

Member
Dec 4, 2018
101
3
18
After adding another 4.0 liters, the issue still did not go away. Truck sat all night and next day work fine. Thinking trim A spool some how came unstuck, or pump was air locked some how?
 
C

Chilly

Member
Dec 4, 2018
101
3
18
After driving around for a bit I am having code: P0659: Actuator supply voltage circuit high, come up all the time.

Key on engine off, code will not re-appear until engine is running. Check engine light will immediately come on. 1 out of every 5 starts, engine light does not come on.

After some research found P0659 is to do with a short to battery voltage. Disconnected PCM connector and checked for 12volts at TCM Pin #11, no voltage. Wiggled wires from TCM plug down to transmission plug, no change. Checked plug on transmission and all wires tight, clean and no corroded pins.

If I clear the code with the engine running, check engine light stays off and I can drive the truck. If the engine light is not cleared, I cannot move the truck and range shift inhibited comes up on the dash.

Trying to find another TCM to try.

Does anyone else have any other suggestions?
 
C

Chilly

Member
Dec 4, 2018
101
3
18
Yes internal harness was replaced. I will see what the ignition voltage is at the TCM and get back to you.
Thanks for the reply.
 
slowdownbrown

slowdownbrown

New member
Jun 15, 2020
1
0
1
40
Austin, TX
Did you figure this out? I'm having the same issue. I've tried a second TCM and traced all wires back through the loom with no issues.
 
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