Malibu, 2004 - 2007.
This problem deals with some unusual transmission shifting and loss of the manual shift while in low.
It seems to downshift way too quickly. For instance, at city speeds of 50km/hr (30mph) if the throttle is let off completely, and then back on even very lightly it feels as if it's downshifting or even slipping. The tach jumps up about 500 - 800 rpm and then right away it shifts back down. As long as the throttle is depressed a bit, things feel normal.
Number 2 effect is when the shifter is pulled back into low, supposedly enabling the +/- button on the shifter for manual shifting. The display on the cluster shows it as in low and 3 but the button has no effect either + or -. In effect the manual shift does not work. The display doesnt change from "3".
The likely cause of both problems is a broken wire in the harness to the +/- switch in the shifter. It's highly unlikely that the switch itself is at fault.
Start by removing the centre console....and sorry, I have no pictures. Perhaps someone could add those sometime
2 torx bolts on either side at the front of the console under 2 small round plastic covers that pop off. To make it easier on the passenger side, the panel between the console and the firewall comes off by pulling outwards on it at the firewall side. It's attached with velcro. Remove the middle (directly to the rear of the shifter) cup holder sleeve and the 2 philips screws under it. Get in the back seat and remove the 2 larger hex bolts on the console on either side at the back. Move the front seats all the way up for easier access. There are other bolts on the console but they dont need to come out, I think they hold the inner parts of the console to the console case.
Once those 6 bolts are out, the console is free. Pull the shifter as far back as you can, into low. Pull up on the back of the console, slide it forward a bit and lift up. There is a small flat plastic piece in front of the cell phone holder that will fall off, dont forget to put it back on when reassembling. With the console up somewhat, there is a wiring harness to the lighter and the traction control switch. Pull the plug from the socket on the harness. The console is now completely free. Lift it up and out of the car.
On the drivers side along the floor and bottom of the shifter there are 2 wiring harnesses. One wraps around from the back to the front of the shifter mechanism and on up into the shifter shaft. This contains 2 wires that go up to the +/- switch. A yellow and pink wire wrapped in a black casing. In my case, it was plain to see at a section with no black casing, the yellow wire was broken right through. It looked like it'd been cut. That was under where the console was, along the floor right beside the shifter on the driver's side.
I then cut the pink wire and spliced in an extra 2 inches or so of comparable wire to each wire. This was soldered, wrapped, and tucked in out of the way. That was it for mine. I reassembled the console and the problems described above were gone. I also took the time to clean under the console while it was out and lubricated the cable and the shifter at any pressure points.
If the break is not as obvious as mine was, you will have to open up the black wrapping on the wires and search for a break. I believe that harness has plugs at one or both ends so you may be able to remove it and work on it out of the car. Be sure to add an additional inch or so since that's why this broke in the 1st place, it was too tight.
The entire job took me about an hour and that includes beer breaks.
It saved me between $100 - $400 depending on who you talk to. Most service centres will probably replace the switch, which isnt necessary.
I have never done this job before now and I am not a professional.
If you are not comfy with attempting this procedure, see a qualified service centre.
BTW, "centre" is the proper spelling in Canada