1A-235 Engine General Information and Diagnosis:
Circuit Description
When the ignition switch is turned ON, the main relay turns ON (the contact point closes) and the main power is
supplied to ECM. And then ECM supplies 5 V power to each sensor (electric load current sensor (for J20 engine),
MAP sensor, A/C refrigerant pressure sensor, APP sensor and TP sensor).
If 5 V power circuit to each sensors from ECM is shorted to ground, ECM stops engine and emission control operation.
Troubleshooting
NOTE
• Before performed troubleshooting, be sure to read the “Precautions of ECM Circuit Inspection: ”.
• When measuring circuit voltage, resistance and/or pulse signal at ECM connector, connect the
special tool to ECM and/or the ECM connectors referring to “Inspection of ECM and Its Circuits: ”.
Step
Action
Yes
No
1
Circuit fuse check
1) Disconnect connectors from ECM with ignition switch
turned OFF.
2) Check for proper connection to ECM connector at “E23-
2”, “E23-29”, “E23-60”, “E23-1”, “E23-16”, “C37-15”,
“C37-30”, “C37-29”, “C37-48” and “C37-58” terminals.
3) If OK, check “RADIO” fuse and “IG COIL” fuse for
blowing.
Are “DOME” fuse and “IG COIL” fuse in good condition?
Go to Step 2.
Replace fuse (s) and
check for short in
circuits connected to
fuse(s).
2
Power supply circuit check
1) Measure voltage between “E23-2” terminal of ECM
connector and body ground.
Is voltage 10 – 14 V?
Go to Step 3.
“WHT” wire is open
circuit.
3
Ignition signal check
1) Turn ignition switch to ON position.
2) Measure voltage between “E23-29” terminal of ECM
connector and body ground.
Is voltage 10 – 14 V?
Go to Step 4.
“BLK/WHT” or “BLK/
YEL” wire is open
circuit.
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