2007 Impala lights flicker 3 cyl mode

When the engine goes from 6 cylinder to 3 cylinder the lights start flickering.
The flickering is like a flicker when you try to raise the power window and it is already up and the lights flicker. BUT the flickering continues until the engine goes back to 6 cylinder mode. The lights flicker the entire time the engine is in 3 cylinder mode. Not just when the mode changes. I have had it to the Chevrolet service department 3 times. Thye can't seem to fix the problem. Anyone have any ideas? Thanks in advance for any help. :banghead:

you have to replace the ignition coil and add a ground strap.there is a bulletin on this.the dealer should have found this bulletin for thi problem.

Thank you Brian. I must have a knuckle head for a service writer. The service manager don't know this either. There is a TSB for this problem. I found it on the internet. I called the chevy dealer and they said they did not know about it. So I informed them sort of politely. TSB #070842008 AND GM document # 1970489 "Replace the ignition coil and add a ground strap". The dealer said he will check into it and call me back. :shakehead Again, Thank you Brian :)