Before you do any servicing or taking your CQ40 apart, do visit the HP page on details about CQ40 blinking code -- link at bottom of this page. Here is the list of the blinking code (taken from HP.com). I suggest you do hard reset and re-seat RAM module. On two occasions, on two units of this model, I just re-seat RAM module, and it works fine. So, sometime, 4x blinking not actually cause by graphic controller problem.
Blinking Code Translation Table
|Number of Blinks or Beeps||Location of Blinking LEDs||Component Being Checked||Error Condition|
|Continuous glow||Battery power LED||Battery||The AC adapter is attached and the battery is charging, but does not yet have sufficient charge to power the notebook.|
|1||Caps Lock/Num Lock||CPU||CPU not functional|
|2||Caps Lock/Num Lock||BIOS||BIOS corruption failure|
|3||Caps Lock/Num Lock||Memory||Module error not functional|
|4||Caps Lock/Num Lock||Graphics||Graphics controller not functional|
|5||Caps Lock/Num Lock||System board||General system board failure|
|6||Caps Lock/Num Lock||BIOS||BIOS authentication failure|
|Continuous blink||AC power adapter LED||Power adapter||Insufficient power|
For more details, please visit this page.