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P0340 - Camshaft Position Sensor Problem. Help !

George Z.

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I recently had my alternator go bad and whenever I'd run my A/C for a long period of time (i.e., 1 hour or more), my charging system was getting low. Long story short, I changed my alternator with another 100-amp one and my A/C and charging are just fine now.

I also went ahead and changed both distributor caps & rotors with "O.E.M." dealer-parts from the local Lexus dealership.

Now, my Check Engine light has turned on and it's Code # (P0340) -- DTC P0340: Camshaft Position (CMP) Sensor CKT Malfunction.

I purchased a NEW Camshaft Position Sensor #1 (Bank #1 - Driver's side) & installed it, and the Check Engine light returned with the same exact code - P0340 (Camshaft Position Sensor #1 Malfunction).

I checked the actual "connections" on the Camshaft Sensor and all the wiring seems to be perfectly normal & fine.

The "symptoms" of the car are as follows:

At idle in park after the car warms up and the idle drops to between 650-700, the idle has a little "play" in it and it moves up and down a bit. It's not surging badly or anything, but the idle is not smooth. Also, if you're in drive and stopped at a light with your foot on the brake, the idle does the exact same thing. When driving and moving down the road, the acceleration feels normally smooth and without hesitation. It's just at a complete stop or idling in park or neutral, it does this...?

Any suggestions or ideas as to what can cause this? Could it be that when the initial alternator was going bad (with the A/C running) that it possibly "shorted-out" a section of the computer or ECM and it's not correctly reading this signal?

Thanks a lot in advance for any help you can provide or suggest to me.

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