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DTC P1491 POSITIVE CRANKCASE VENTILATION (BLOW-BY) FUNCTION PROBLEM

DTC P1491 POSITIVE CRANKCASE VENTILATION (BLOW-BY) FUNCTION PROBLEM

DTC DETECTING CONDITION:


• Two consecutive driving cycles with fault

• GENERAL DESCRIPTION


TROUBLE SYMPTOM:

Erroneous idling

Important

After repair or replacement of faulty parts, conduct Clear Memory Mode and Inspection Mode .


WIRING DIAGRAM:


CHECK BLOW-BY HOSE.

Check the blow-by hose.

Is there disconnection or crack in blow-by hose?

Yes

Replace or repair blow-by hose.


No


INSPECT HARNESS BETWEEN PCV DIAGNOSIS CONNECTOR AND ECM CONNECTOR.

Turn the ignition switch to OFF.

Disconnect the connector from PCV diagnosis connector and ECM.

Measure the resistance of harness between PCV diagnosis connector and ECM connector.

Connector & terminal

(B137) No. 2 — (E61) No. 2:

Is the resistance less than 1 Ω?

Yes


No

Repair open circuit in harness between PCV diagnosis connector and ECM.


INSPECT HARNESS BETWEEN PCV DIAGNOSIS CONNECTOR AND ECM CONNECTOR.

Measure the resistance of harness between PCV diagnosis connector and chassis ground.

Connector & terminal

(B137) No. 2 — Chassis ground:

Is the resistance more than 1 MΩ?

Yes


No

Repair short circuit to chassis ground in harness between PCV diagnosis connector and ECM.


INSPECT PCV DIAGNOSIS CONNECTOR GROUND CIRCUIT.

Measure the resistance between PCV diagnosis connector and engine ground.

Connector & terminal

(B61) No. 1 — Engine ground:

Is the resistance less than 5 Ω?

Yes


No

Repair PCV diagnosis connector ground circuit.


INSPECT PCV DIAGNOSIS CONNECTOR.

Measure the resistance between PCV diagnosis connector and terminal.

Terminals

No. 1 — No. 2:

Is the resistance less than 1 Ω?

Yes

Repair poor contact in ECM and PCV diagnosis connector.


No

Replace PCV diagnosis connector.