Subaru Impreza 2003, Service Manual

Page: 864 / 3610

EN(H4SOw/oOBD)-88
ENGINE (DIAGNOSTICS)
DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
1)Disconnect the connector from manifold
absolute pressure sensor.
2)Turn the ignition switch to ON.
3)Measure the voltage between manifold
absolute pressure sensor connector and
engine ground.
Connector & terminal
(E20) No. 3 (+) — Engine ground (–):
Is the voltage 4.5 — 5.5 V? Go to step 2. Repair the open or
ground short cir-
cuit in harness
between ECM and
manifold absolute
pressure sensor.
2 CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
1)Disconnect the connector from ECM.
2)Measure the resistance of harness between
ECM and manifold absolute pressure sensor
connector.
Connector & terminal
(B136) No. 16 — (E20) No. 1:
(B136) No. 5 — (E20) No. 4:
Is the resistance less than 1
Ω
?
Go to step 3. Repair the open
circuit in harness
between ECM and
manifold absolute
pressure sensor
connector.
3 CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
Measure the resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B136) No. 5 — Chassis ground:
(B136) No. 16 — Chassis ground:
Is the resistance more than 1
M
Ω
?
Go to step 4. Repair the ground
short circuit in har-
ness between
ECM and mani-
fold absolute pres-
sure sensor
connector.
4 CHECK INPUT SIGNAL FOR ECM.
1)Turn the ignition switch to OFF.
2)Connect the connector to ECM and manifold
absolute pressure sensor.
3)Turn the ignition switch to ON.
4)Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B136) No. 5 (+) — Chassis ground (–):
Is the voltage 2.3 — 2.5 V? Go to step 5. Replace the mani-
fold absolute pres-
sure sensor. <Ref.
to FU(H4SOw/
oOBD)-34, Intake
Air Temperature
and Manifold
Absolute Pres-
sure Sensor.>
5 CHECK INPUT SIGNAL FOR ECM.
1)Start the engine, and idle it.
2)Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B136) No. 5 (+) — Chassis ground (–):
Is the voltage 1.2 — 1.8 V? Go to step 6. Replace the mani-
fold absolute pres-
sure sensor. <Ref.
to FU(H4SOw/
oOBD)-34, Intake
Air Temperature
and Manifold
Absolute Pres-
sure Sensor.>
6 CHECK POOR CONTACT.
Check poor contact in manifold absolute pres-
sure sensor connector.
Is there poor contact in mani-
fold absolute pressure sensor
connector? Repair the poor
contact in manifold
absolute pressure
sensor connector. Replace the mani-
fold absolute pres-
sure sensor. <Ref.
to FU(H4SOw/
oOBD)-34, Intake
Air Temperature
and Manifold
Absolute Pres-
sure Sensor.>