I have recently inherited a MacBook Pro which occasionally reboots at random. It has 4Gb Ram (2X2). AHT is consistently showing a 4MEM error - e.g. '4MEM/66/40000000:0xa1e45898'

Diagnostics so far:

  • Re-seating/cleaning modules - same 4MEM errors.
  • Swapping modules between sockets - 4MEM error with different 0x value.
  • Testing modules individually - no errors (in either socket).

The above seems to rule out the memory modules or the sockets. Errors only occur when both modules are plugged in. Could this be a timing problem between modules? (Original Apple memory).

I have tried resetting PRAM and SMC - same errors occurring.

Any suggestions as to where to go next most welcome.

  • 1
    When you swapped the memory modules, the problem moved. If it was the sockets, the problem would have stayed the same. Try getting new modules.
    – Allan
    Commented Jan 4, 2017 at 11:48

1 Answer 1


Seems it was the memory module(s). Installed two new 2Gb modules and ran AHT extended overnight. No errors.

  • That's good news. Though, the MBP Mid-2010 can take 8GB RAM; I would have put two 4GB modules in there. If you are within the return period exchange them, this is the route I would take. You will notice an immediate improvement
    – Allan
    Commented Jan 11, 2017 at 3:52

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