When troubleshooting, use the schematic to locate these standard rails. While the exact page numbers vary by revision, most LA-G121P diagrams follow Intel/AMD standard power delivery:
Symptoms: Resistance to ground is 3 Ohms on the 3.3V rail.
Diagnosis: Blown capacitor or shorted EC.
How the schematic helps: Search the PDF for +3.3V_ALW. The schematic lists every single component on that net. la-g121p schematic
What to check: If you have no +3.3V_ALW, the laptop will never turn on. The schematic shows that AC_IN (BQ24780S pin 5) must go high to ACDET (2.4V). If ACDET is wrong, check resistors PR36 and PR37. When troubleshooting, use the schematic to locate these