1A-91 Engine General Information and Diagnosis:
DTC “C40” (P0505 / P0506 / P0507): ISC Valve Circuit Malfunction
B718H11104022
Detected Condition and Possible Cause
Wiring Diagram
ECM coupler (Harness side)
Troubleshooting
CAUTION
!
• Be careful not to disconnect the ISC valve coupler at least 5 seconds after ignition switch is turned
to OFF.
If the ECM coupler is disconnected within 5 seconds after ignition switch is turned to OFF, there is a
possibility of an usual valve being written in ECM and causing an error of ISC valve operation.
• When using the multi-circuit tester, do not strongly touch the terminal of the ECM coupler with a
needle pointed tester probe to prevent the terminal damage or terminal bend.
NOTE
After repairing the trouble, clear the DTC using SDS tool. Refer to “Use of SDS Diagnosis Reset
Procedures (Page 1A-13)”.
Detected Condition Possible Cause
C40/P0505
The circuit voltage of motor drive is
unusual.
• ISC valve circuit open or shorted to the ground.
C40/P0506
Idle speed is lower than the desired idle
speed.
• Air passage clogged.
• ISC valve is fixed.
• ISC valve preset position is incorrect.
C40/P0507
Idle speed is high than the desired idle
speed.
• Disconnect ISC valve hose.
• ISC valve is fixed.
• ISC valve preset position is incorrect.
ECM
IS1B
IS1A
IS2B
IS2A
ISC valve
Lbl
W/Y
Lg
Dbr
Lbl
W/Y
Lg
Dbr
36
48
49
35
I718H1110105-03
I718H1110240-01
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