DTC P1491 Positive Crankcase Ventilation (Blow-By) Function Problem

WARNING: This page is about a different variant/trim than selected.

DTC DETECTING CONDITION:

Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION < Ref. to DTC P1491 POSITIVE CRANKCASE VENTILATION (BLOW-BY) FUNCTION PROBLEM , Diagnostic Trouble Code (DTC) Detecting Criteria. >

TROUBLE SYMPTOM:

Erroneous idling

CAUTION: After repairing or replacing the defective part, perform the Clear Memory Mode < Ref. to OPERATION , Clear Memory Mode. > and Inspection Mode < Ref. to PROCEDURE , Inspection Mode. >.

WIRING DIAGRAM:

Fig 1: Positive Crankcase Ventilation (Blow-By) Function Problem - Wiring Diagram

DIAGNOSIS PROCEDURE

Step	Check	Yes	No
1 CHECK BLOW-BY HOSE. Check the condition of the blow-by hose.	Is there any disconnection or crack in blow-by hose?	Replace or repair the blow-by hose.	Go to step 2 .
2 CHECK HARNESS BETWEEN PCV DIAGNOSIS CONNECTOR AND ECM CONNECTOR. Turn the ignition switch to OFF. Disconnect the connectors from the PCV diagnosis connector and ECM. Measure the resistance of harness between PCV diagnosis connector and ECM connector. Connector & terminal (B134) No. 30 - (E61) No. 2:	Is the resistance less than 1 Ω?	Go to step 3.	Repair the open circuit of harness between PCV diagnosis connector and ECM connector.
3 CHECK HARNESS BETWEEN PCV DIAGNOSIS CONNECTOR AND ECM CONNECTOR. Measure the resistance of harness between PCV diagnosis connector and chassis ground. Connector & terminal (B134) No. 30 - Chassis ground:	Is the resistance more than 1 MΩ?	Go to step 4.	Repair the ground short circuit of harness between PCV diagnosis connector and ECM connector.
4 CHECK GROUND CIRCUIT OF PCV DIAGNOSIS CONNECTOR. Measure the resistance of harness between PCV diagnosis connector and engine ground. Connector & terminal (E61) No. 1 - Engine ground:	Is the resistance less than 5 Ω?	Go to step 5.	Repair the ground circuit of PCV diagnosis connector.
5 CHECK PCV DIAGNOSIS CONNECTOR. Measure the resistance between PCV diagnosis connector terminals. Terminals No. 1 - No. 2:	Is the resistance less than 1 Ω?	Repair the poor contact in ECM connector and PCV diagnosis connector.	Replace the PCV diagnosis connector.