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Old 11-12-2013, 05:27 PM   #75
SubNub
Scooby Newbie
 
Member#: 53603
Join Date: Jan 2004
Location: NORCAL AND SOCAL
Vehicle:
2004 EJ207 WRX
PSM

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Add me to the list of cars with this P0340 CEL problem. Mine is a 2005 JDM EJ207 engine swapped into a USDM WRX. So far I know this:

1. It threw the CEL after the car sat for 3 days. It would barely start and barely IDLE. Only thing that kept it running was the warmup idle. Above 2kRPM, the engine was perfectly smooth.
2. After swapping in the EJ207, my USDM alternator has made a whining noise that is RPM dependent. It's NOT the A/C idler pulley as I have changed that.
3. I removed the battery side Cam Position Sensor, cleaned the sensor, cleaned the connector with MAF cleaner and applied dielectric grease to the connector. It was better for the first start but I think this was likely due to removing the battery which reset the ECU and cleared the code.
4. Shortly after cleaning the sensor connection, it threw the CEL after I changed my oil and had been charging my iPhone and running the radio for entertainment during the change (~1 hour taking my time) with the key on accessory. The idle again was very choppy but seemed to resolve after starting to drive. I could feel hesitation at 2K RPM for a moment in second gear though. Everywhere else felt fine.

Conclusions:
A. I theorize that I only seem to have an issue when the charge on my battery is low. I believe my alternator may not be putting out ample voltage due to the whine, especially below 2k RPMs.
B.The CAM Position Sensor must be very sensitive to electrical voltage, interference etc.
i. I've seen people say they fixed the issue with a grounding mod.
ii. I've seen others who have done the grounding mod but have a whining alternator also experience the problem

So, what do you guys think? I don't have a multimeter handy at the moment to check things out but it seems like a low battery may be at least part of the equation! I never had this issue on my USDM EJ205 though...Is it possible the sensor only becomes this sensitive to electrical disturbances when the sensor is failing?
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Last edited by SubNub; 11-12-2013 at 06:45 PM.
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