Nissan Altima 2007-2012 Service Manual: P1421 Cold start control


ECM controls ignition timing and engine idle speed when engine is started with prewarming up condition.

This control promotes the activation of three way catalyst by heating the catalyst and reduces emissions.

DTC Logic


NOTE: If DTC P1421 is displayed with other DTC, first perform the trouble diagnosis for other DTC.




If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at least 10 seconds before conducting the next test.

TESTING CONDITION: Before performing the following procedure, confirm that battery voltage is more than 11V at idle.

>> GO TO 2.


1. Turn ignition switch OFF and wait at least 10 seconds.

1. Turn ignition switch OFF and wait at least 10 seconds.

2. Turn ignition switch ON.

3. Select

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