engine stumbles in cruise with turn signal on

[letsgo]

This is a first for me, but I think this has been posted before.

I'm traveling at 65mph in cruise control and put the right hand turn signal on, the engine stumbled or slowed down, I immediatly put my foot on the gas (diesel) pedel to speed up and switched off cruise control at the same time NO PROBLEM. I then tried to simulate the same fault it took between 10 to 20 tries It did happen again, it will go back to the dealers.

I'm looking for suggestions as to the fault, (is it the turn signal switch?) or ???? Also is there a GMC bulletin covering this problem?

any help welcomed.

[Max Power]

Most likely the wiring in the turn signal lever is broken. It will likely get worse with more use and time. This used to be very common on GM vehicles. Not so common now but they still use the same basic idea. A new multi function lever (turn signal, 4 ways, cruise, wipers, headlight dimmer all in one) Is around $200 and takes approx 1/2 to an hour to change.

[Modified]

My guess would be a intermittant CC switch, broken wire, or a loose connection in your cruise control switch or wiring, which is being irritated when your blinker lever is getting moved. A loss of power to the CC may be the same as turning it off, just a hunch. These wires are 22 gauge, (very small), and they may be fragil.
The CC for a 2002 Duramax has the following four wires, which one is power, and three go to the ECM:

Wire 41 (BRN) 12V power from CRUISE Fuse 10A
Wire 397 (GRY) Cruise Control On
Wire 84 (DK BLU) Set/Coast
Wire 87 (GRY/BLK) Resume/Accel

I would first look at the BRN and GRY wires. The other two wires only get 12V when the Set/Coast or Resume/Accel are depressed.
Between the CC switches, and the Fire Wall Penetration P100, is Connector C201, which is a larger, 48 pin rectangular connector, mounted on or near the steering column under dash. This most likely would not be flexed or disturbed during Turn Signal operation. The above wires go to pins **3, **2, **4, and **5 of C201 respectively.
The cruise control is powered by its own fuse, independent of blinker power. I looked briefly through Helms manual and saw no electrical link between CC and the blinkers.
Reference Helms 2002 pages 8-863, 8-223, 8-87. Hope this helps.