Built-In Self-Test (Bist) - Dell Inspiron 7706 Service Manual

Table 19. LED codes (continued)
Diagnostic light codes
2,2
2,3
2,4
2,5
2,6
2,7
3,1
3,2
3,3
3,4
Camera status light: Indicates whether the camera is in use.
● Solid white — Camera is in use.
● Off — Camera is not in use.
Caps Lock status light: Indicates whether Caps Lock is enabled or disabled.
● Solid white — Caps Lock enabled.
● Off — Caps Lock disabled.

Built-in self-test (BIST)

There are three different types of BIST to check the performance of display, power rail, and system board. These tests are
important to evaluate if an LCD or system board needs a replacement.
1. M-Bist: M-BIST is the system board built-in self-test diagnostics tool that improves the diagnostics accuracy of system
board embedded controller (EC) failures. M-BIST must be manually initiated before POST and can also run on a dead
system .
2. L-BIST: L-BIST is an enhancement to the single LED error code diagnostics and is automatically initiated during POST.
3. LCD-BIST: LCD BIST is an enhanced diagnostic test that is introduced through Preboot System Assessment (PSA) on legacy
systems.
Table 20. Functions
Purpose
Trigger
Indicator of fault
Repair instruction
Problem description
System board: BIOS or ROM (Read-Only
Memory) failure
No memory or RAM (Random-Access Memory)
detected
Memory or RAM (Random-Access Memory)
failure
Invalid memory installed
System-board or chipset error
Display failure
Coin-cell battery failure
PCI, video card/chip failure
Recovery image not found
Recovery image found but invalid
M-BIST
Evaluates the health condition of the
system board.
Press the <M> key and power button.
Battery LED light with Solid Amber.
Indicates a problem with the system
board.
L-BIST
Checks if the system board is supplying
power to the LCD by performing an LCD
Power Rail test.
Integrated into the single LED error code
diagnostics. Automatically initiated
during POST.
Battery LED error code of [2,8] blinks
Amber x2, then pause, then blinks White
x8.
Indicates a problem with the system
board.
Troubleshooting 69