Subaru IMPREZA 2004 Service Manual page 775

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
8 CHECK INPUT VOLTAGE FOR ECM.
1)Turn the ignition switch to OFF.
2)Connect the connector to ECM and oxygen
sensor.
3)Set the oscilloscope probe at ECM connec-
tor terminal positive (+) and its ground lead at
negative (–).
4)Start the engine.
9 CHECK POOR CONTACT.
Check poor contact in ECM connector.
Do 0.1 and 1 V waveform pat-
terns alternately appear on the
oscilloscope screen?
Is there poor contact in ECM
connector?
EN(H4SOw/oOBD)(diag)-79
Check
Go to step 9.
Replace the oxy-
gen sensor con-
nector.
ENGINE (DIAGNOSTICS)
Yes No
Replace the oxy-
gen sensor.
Replace the ECM.
<Ref. to
FU(H4SOw/
oOBD)-43, Engine
Control Module
(ECM).>