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P1391 = Intermittent loss of CMP or CKP.
Since the problem is weather related, the most likely cause would be contaminated terminal joints. Unplug the CMP and CKP connectors to check for contaminataions or loose connections.
Is your vehicle a 3.3 or 3.8 L engine?
Thursday, December 31st, 2009 AT 12:02 PM