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fault code p1391

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Dec 22, 2005, 4:19 AM

Post #1 of 3 (31856 views)
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i have a 1999 dodge dakota 6 cylinder. i got fault p1391 about 2 weeks ago. hooked computer to it said tune-up. did spark plugs, wires, dist cap, rotor and pcv valve. truck still keeps giving fault and runs like it is dying after about 5 to 7 miles in the morning. it runs like it is missing 2 or 3 cylinders...backfiring and choking to death. if i stop and let it sit for 10 to 15 minutes it will run fine until the next morning. help please anyone.....
update.....i have found the fault code says intermitant loss of camshaft or crankshaft sensor....i am going to try that. will be back if does not fix the problem....

(This post was edited by two8pts on Dec 22, 2005, 11:27 AM)

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DanD profile image

Dec 22, 2005, 11:36 AM

Post #2 of 3 (31836 views)
Re: fault code p1391 [In reply to] Sign In

I don’t know where you got the idea that a code P1391 means you need to tune your truck up, because this code stands for intermittent loss of camshaft or crankshaft position sensor signal. Which has nothing to do with the secondary ignition system (plugs, wires, cap and rotor) I’m not saying the truck didn’t need a tune-up and it never hurts anyway, if it hadn’t had one in a while.
As for diagnosing whether it’s in the wiring, sensors or the computer you almost need an oscilloscope connected to either circuit. That’s so you can watch the wave form pattern coming off of the sensors. This is while the engine is running and doing its thing, in the hope of seeing a glitch in the pattern.
Short of that it’ll be a complete guess as to what or who is causing the problem. I’m going to suggest taking the truck in and have someone figure this one out for you.
If you’re starting to think of changing the cam sensor yourself, be careful because you need a scan tool to synchronize it to the rest of the ignition system.

Canadian "EH"

New User

Dec 23, 2005, 3:40 PM

Post #3 of 3 (31824 views)
Re: fault code p1391 [In reply to] Sign In

the guy at advance auto told me that code p1391 was for tune-up which it is not...i know now. i changed the crankshaft sensor yesterday and it appears to have fixed the problem. thank you for your response.

fault code p1391

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