Subaru Legacy 2004 Service Manual page 1395

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
7 CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start and warm-up the engine until engine
coolant temperature is greater than 60!C
(140!F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all accessory switches to OFF.
5) Open the hood.
6) Measure the ambient temperature.
7) Read the data of mass air flow and intake
air temperature sensor signal using Subaru
Select Monitor.
NOTE:
For detailed operation procedure, refer to
"READ CURRENT DATA SHOWN ON DIS-
PLAY FOR
EN(H4DOTC)(diag)-21, Subaru Select Moni-
tor.>
ENGINE". <Ref. to
EN(H4DOTC)(diag)-106
Check
Subtract the ambient tempera-
ture from intake air tempera-
ture, and is the value from "
10!C (14!F) to 50!C (122!F)?
Yes
Replace the ECM. Check mass air
<Ref. to flow and intake air
FU(H4DOTC)-35, temperature sen-
Engine Control sor. <Ref. to
Module (ECM).> FU(H4DOTC)-28,
Mass Air Flow and
Intake Air Temper-
ature Sensor.>
No