Subaru Legacy 2003 Service Manual page 2032

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK POWER SUPPLY TO DIFFEREN-
TIAL PRESSURE SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from differential
pressure sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between differential
pressure sensor and engine ground.
Connector & terminal
(B221) No. 1(+) — Engine ground ( − − − − ):
Does the measured value exceed the spec-
ified value?
2 CHECK HARNESS BETWEEN ECM AND
DIFFERENTIAL PRESSURE SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM and
differential pressure sensor.
Connector & terminal
(B221) No. 2 — (B135) No. 19:
(B221) No. 3 — (B135) No. 15:
Is the measured value less than the speci-
fied value?
3 CHECK HARNESS BETWEEN ECM AND
DIFFERENTIAL PRESSURE SENSOR.
Measure the resistance between differential
pressure sensor and engine ground.
Connector & terminal
(B221) No. 3 — engine ground:
Does the measured value exceed the specified
value?
4 CHECK DIFFERENTIAL PRESSURE SEN-
SOR.
1) Turn the ignition switch to OFF.
2) Install the vacuum pump to secondary tur-
bocharger side hose fitting.
3) Apply 5 V to the terminals No.1 and No.2,
then connect terminal NO.3 to positive side
and terminal No.2 to negative side.
4) Measure the voltage between differential
pressure sensor terminals.
Terminal
No. 3 (+) — No. 2 ( − − − − ):
Does the voltage change as in the specified
range?
5 CHECK POOR CONTACT.
Check poor contact in ECM and differential
pressure sensor connectors.
Is there poor contact in ECM and differential
pressure sensor connectors.
Value
4.5 V
1 Ω
1 MΩ
3.5 V at 66.7 kPa (500 mmHg,
19.69 inHg)
2.0 V at 0 kPa (0 mmHg, 0
inHg)
0.5 V at -66.7 kPa (-500
mmHg, (-19.69 inHg)
There is poor contact.
EN(H4DOSTC)-193
ENGINE (DIAGNOSTICS)
Yes
Go to step 2. Repair or replace
the harness con-
nector between
ECM and differen-
tial pressure con-
nector.
Go to step 3. Repair the open
circuit between
ECM and differen-
tial pressure sen-
sor.
Go to step 4. Repair the ground
short circuit
between ECM and
differential pres-
sure sensor.
Go to step 5. Replace the differ-
ential pressure
sensor.
Repair the poor Replace the ECM.
contact in ECM
and differential
pressure sensor
connectors.
No