'''The fans kick into high '''by default when a temp sensor fails to keep from cooking the CPU or other components like a GPU.
You have damaged RAM, and possibly other problems.
• 2 Flashes: No RAM is installed or detected (could be bad RAM).
• 3 Flashes: Incompatible RAM types are installed.
• 4 Flashes: No RAM banks passed memory testing.
• 5 Flashes: No good boot images are detected in the boot ROM (and/or there is a bad
sys config block).
• 6 Flashes: The processor is not usable.
Replacing the PRAM battery is good idea - the battery is recharged when the computer is plugged in, but the life of a battery is at most 5 years. PRAM Information includes:
* Speaker volume
* Screen resolution
* Startup disk selection
* Recent kernel panic information, if any
If you experience issues related to these functions, you may need to reset the NVRAM or PRAM.
''Resetting the SMC or PRAM is not a "fix" it should only be done as part of a troubleshooting process.''
''If this answer is acceptable '''please remember to return and mark it'''.''