Apple MacBook Pro 17-inch (original, Core 2 Duo, 2.4GHz, Late 2007 CTO, Early 2008, and Late 2008) - Manual (Page 185)

MacBook Pro 17-inch (original, Core 2 Duo, 2.4/2.6GHz, 2008) Troubleshooting — Hardware Symptom Charts 185
Verify known-good analog (not digital) telephone line. 2.
Verify known-good RJ-11 telephone cable. 3.
Verify RJ-11 cable is not plugged into Ethernet port (should not be physically possible with 4.
this MacBook Pro).
Verify RJ-11 telephone cable is firmly installed in the modem port. 5.
Inspect RJ-11 connector for pin damage. If damaged, replace modem. 6.
Open Apple System Profiler, and look for Apple External Modem in the USB Device Tree 7.
under the Hardware tab. If it does not appear, check the modem USB connection.
Update the system software. 8.
Try a known-good Apple USB modem in all USB ports. If it does not work in either of the two 9.
left USB ports, replace the left I/O board. If it does not work in the right USB port, replace the
logic board.
Modem does not respond (can hear dial tone)
Check that the correct modem is selected in the Network Port Configuration section of the 1.
Network system preferences.
Check that the modem application is properly configured. 2.
Open Apple System Profiler, and under the Software tab look at Extensions. Check to see that 3.
the MotorolaSM56K and AppleI2SModem Family files are listed and loaded. If not, restart the
system and check again. If still not visible, replace system software.
Open Apple System Profiler, and look for Apple External Modem in the USB Device Tree 4.
under the Hardware tab. If it does not appear, check the modem USB connection.
Replace the Apple USB Modem. 5.
Replace the logic board. 6.
Modem intermittently disconnects or low performance
Verify known-good RJ-11 telephone cable (for example, the retaining clip is not broken off) 1.
and check that it is firmly installed when used. If telephone cable is bad, replace it.
If the issue happens with only one particular phone line, but not another, the problem may 2.
be an issue with that phone line. Under bad line conditions, try setting the modem script to
start with a slower connect rate such as “Apple Internal 56K Modem (v.34).”
If the customer indicates the system disconnects under very high CPU loads such as burning 3.
DVDs and/or working with video editing software such as Final Cut Pro, try connecting the
modem without any application running and see how the modem performs. Use Knowledge
Base article 106642: Mac OS X: Using Apple PPP Test Server to test the modem. If OK, suggest
to the customer to use the modem with less applications running simultaneously.
Replace the Apple USB modem. 4.
Replace the logic board. 5.