Subaru Legacy 2005 Service Manual page 1324

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
2 CHECK INPUT SIGNAL OF ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 16 (+) — Chassis ground (
3 CHECK INPUT SIGNAL OF ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 22 (+) — Chassis ground (
4 CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from manifold
absolute pressure sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between manifold
absolute pressure sensor connector and
engine ground.
Connector & terminal
(E21) No. 3 (+) — Engine ground (
5 CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness
between ECM and manifold absolute pressure
sensor connector.
Connector & terminal
(B136) No. 22 — (E21) No. 2:
6 CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
Measure the resistance of harness between
ECM and manifold absolute pressure sensor
connector.
Connector & terminal
(B136) No. 35 — (E21) No. 1:
7 CHECK POOR CONTACT.
Check poor contact in manifold absolute pres-
sure sensor connector.
Check
Does the voltage change by
shaking the harness and con-
nector of ECM while monitor-
ing the value with voltage
−
): meter?
Is the voltage more than 4.5 V? Go to step 4.
−
):
Is the voltage more than 4.5 V? Go to step 5.
−
):
Is the resistance less than 1
Ω?
Is the resistance less than 1
Ω?
Is there poor contact in mani-
fold absolute pressure sensor
connector?
EN(H4DOTC)(diag)-84
Yes
Repair the poor Replace the ECM.
contact in ECM <Ref. to
connector. FU(H4DOTC)-34,
Engine Control
Module (ECM).>
Replace the ECM.
<Ref. to
FU(H4DOTC)-34,
Engine Control
Module (ECM).>
Repair the open
circuit of harness
between ECM and
manifold absolute
pressure sensor
connector.
Go to step 6. Repair the open
circuit of harness
between ECM and
manifold absolute
pressure sensor
connector.
Go to step 7. Repair the open
circuit of harness
between ECM and
manifold absolute
pressure sensor
connector.
Repair the poor Replace the mani-
contact in mani- fold absolute pres-
fold absolute pres- sure sensor. <Ref.
sure sensor to FU(H4DOTC)-
connector. 28, Manifold Abso-
lute Pressure Sen-
sor.>
No