It’s most likely the solenoid in the gear selector. Try lubricating the plunge.
That extra ground wire doesn’t resolve the ground wire issue, trace back the ground wire for the TCM look for loose ground wire, it attaches to the driver’s side strut tower.
changing the gear selector is 4 … 10 mm fasteners and the shift cable and the light in the PRNDL

 

Hello, strange thing i sold the car last friday but, after 2 year of fighting i managed to solve the problem!

My solution was so simple i cant belive it! Listen

The door lock was worn out, so the chip in the door thinks that door are open when You drive (D), my solution was to use the Insulating tape on all the metals that door are hooker when You close them, the metal things on the body where the lock locks. make a coatin from Insulating tape on them i made 10 spins, problem solved.

I miss my HHR

 

Hello, thank you for replying after all these years 🙃. It’s good to hear that you eventually found a solution after all your attempts. I don’t think the Chevy Tahoe and the HHR are very similar internally.

I don’t think the same solution will work for me because my car is a 2007 Tahoe When the door opens while driving, the car does not shift into P like modern cars do.

I thought my problem might be similar to yours because while driving the gear keeps switching repeatedly between D and P, and sometimes 2, along with all the doors locking and unlocking and a loss of power.

However, when the car comes to a complete stop nothing happens. But when I stop and put the car in N, and then press the gas pedal, it starts switching repeatedly between D and P.

 

How could you be facing the same problem with your Tahoe? Completely different gear selector design.

 

What would i do check all the grounds in the car, check all the abs sensors, and check the cables in doors, specaly the wires betwen door and body, start from the driver side. If that will not help check the shifter solenoid. And maybe the transmission gear fluid is low or old ? What was checked in my HHR is BCM and the comfort module (in my chevy they ware glued solid) Also try to tighten the fuse boxes.

I think that you may also chec the locking system.

I dont know the tahoe car.

 

Thank you for your replay , I'll check everything you mentioned

 

The description of his problem with his HHR is very similar to my problem. Also, since both are Chevy, I thought there might be some similarity.

 

Nope other than the bow tie , your selector is on the steering column, the HHR is on the floor
parts supplier might be the same but the parts are of a different design.
I agree to try some of the things in the above posts .