IBM pSeries 690 Service Manual page 270

Step 152f-55
Turn off the power.
Make sure all amber logic-power LEDs of all installed processor subsystem DCAs are off.
Step 152f-56
Has the system backplane been replaced?
Yes Call for support.
No Go to "Step 152f-52" on page 253.
254 Eserver pSeries 690 Service Guide