Dell Enhanced Pre-Boot System Assessment - Epsa Diagnostic 3.0; Built-In Self-Test (Bist); M-Bist; Lcd Power Rail Test (L-Bist) - Dell Latitude 7490 Owner's Manual

Dell Enhanced Pre-Boot System Assessment — ePSA
Diagnostic 3.0
You can invoke the ePSA diagnostics by either of the following ways :
● Press the F12 key when the system posts and choose ePSA or Diagnostics option on One Time Boot Menu.
● Press and hold Fn(Function key on keyboard) and Power On (PWR) the system.

Built-in self-test (BIST)

M-BIST

M-BIST (Built In Self-Test) is the system board's built-in self-test diagnostics tool that improves the diagnostics accuracy of
system board embedded controller (EC) failures.
M-BIST can be manually initiated before POST (Power On Self Test).
NOTE:
How to run M-BIST
M-BIST must be initiated on the system from a power-off state either connected to AC power or with battery only.
NOTE:
1. Press and hold both the M key on the keyboard and the power button to initiate M-BIST.
2. With both the M key and the power button held down, the battery indicator LED may exhibit two states:
a. OFF: No fault detected with the system board
b. AMBER: Indicates a problem with the system board
3. If there is a failure with the system board, the battery status LED will flash one of the following error codes for 30 seconds:
Table 18. LED error codes
Blinking Pattern
Amber
2
2
1
2
4. If there is no failure with the system board, the LCD will cycle through the solid color screens described in the LCD-BIST
section for 30 seconds and then power off.

LCD Power rail test (L-BIST)

L-BIST is an enhancement to the single LED error code diagnostics and is automatically initiated during POST. L-BIST will check
the LCD power rail. If there is no power being supplied to the LCD (i.e., the L-BIST circuit fails), the battery status LED will flash
either an error code [2,8] or an error code [2,7].
If L-BIST fails, LCD-BIST cannot function as no power will be supplied to the LCD.
NOTE:
How to invoke L-BIST Test:
1. Press the power button to start the system.
2. If the system does not start up normally, look at the battery status LED:
● If the battery status LED flashes an error code [2,7], the display cable may not be connected properly.
White
1
8
1
4
Possible Problem
CPU Failure
LCD Power Rail Failure
TPM Detection Failure
Unrecoverable SPI Failure
Troubleshooting 87