Apple M8347LL/A User Guide - Page 144

Troubleshooting Resetting the PMU on the Logic Board - 1 2 Resetting the PMU on the Logic Board Resetting the PMU (Power Management Unit) on the logic board can resolve many system problems. Whenever you have a unit that fails to power up, you should follow this procedure before replacing any modules. 1. Disconnect the power cord and check the battery in the battery holder (BT1). The battery should read 3.3 to 3.7 volts. If the battery is bad, replace the battery, wait ten seconds, and then reset the PMU (refer to the next step). If the battery is good, go to the next step. 2. Press the PMU reset switch (S1) once on the logic board and then proceed to step 3. Do NOT press the PMU reset switch a second time because it could crash the PMU chip. 3. WAIT ten seconds before connecting the power cord and powering the computer on. If the computer powers on, go to the next step. If the computer does not power on, there is something else wrong with the computer, refer to the symptom/ cure chart, "No Power" in this chapter. 4. Run MacTest Pro and return the computer to the customer. Note: This entire procedure resets the computer's PRAM. Be sure to reset the computer's time, date and other system parameter settings before returning the computer to the customer.