Subaru Legacy 2003 Service Manual page 534

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK ANY OTHER DTC ON DISPLAY.
Is any other DTC displayed?
2 CHECK THERMOSTAT.
Does thermostat remain opened?
Value
DTC indicated.
Thermostat remains opened.
EN(H4SO)-137
ENGINE (DIAGNOSTICS)
Yes
Inspect the rele- Go to step 2.
vant DTC using
"List of Diagnostic
Trouble Code
(DTC)". <Ref. to
EN(H4SO)-83, List
of Diagnostic
Trouble Code
(DTC).>
NOTE:
In this case, it is
not necessary to
inspect DTC
P0125.
Replace thermo- Replace engine
stat. <Ref. to coolant tempera-
CO(H4SO)-21, ture sensor. <Ref.
Thermostat.> to FU(H4SO)-26,
Engine Coolant
Temperature Sen-
sor.>
No