A few days ago my MacBook Pro 15″ (early 2011) has stopped to work properly because of faulty discrete graphic card (many other owners are reporting the same problem in Apple forums), but with this problem I’d experienced another one: when I was closing the lid (or clamshell), MacBook Pro didn’t want to go in sleeping mode.
While for the first issue I had to sent in assistance, the second one I’ve fixed myself reading on some forums a trick.
If the reset of SMC doesn’t work in your case, try this:
- Find where the magnets, that permits the sleep, are located (I’ve used a clip). On my MacBook one is on the left of the screen and its counterpart is on the left of the keyboard
- With a magnet (or a piece of steel or anything that is attracted by a magnet, I’ve used a Jot Pro capacitive stylus) pass it a few times on both the magnets of the MacBook
After that I’ve turned on my Mac, closed the lid and.. it went to sleep!
If it doesn’t work try to check if the Reed Switch cable is well connected (should be near the RAM slots) and if it still doesn’t work probably you’ve a faulty sleep sensor.