Manual

Aboutthismanual

ThismanualcontainsserviceandreferenceinformationforthefollowingThinkPad

products.

ThinkPadT420andT420iMachineType4177,4178,4179,4180,4236,4237,and4238

Usethismanualalongwiththeadvanceddiagnosticteststotroubleshootproblems.

Important:

ThismanualisintendedonlyfortrainedservicetechnicianswhoarefamiliarwithThinkPadproducts.Usethis

manualalongwiththeadvanceddiagnosticteststotroubleshootproblemseffectively.

BeforeservicingaThinkPadproduct,besuretoreadalltheinformationunderChapter1“Safetyinformation”on

page1andChapter2“Importantserviceinformation”onpage23.

iii