Subaru P0340

Robert Owner/Technician New York Posted   Latest  
2009 Subaru Forester X Premium 2.5L (EJ253) 4-spd (TZ1B8) — JF2SH63669H754055
P0340 — Camshaft Position Sensor "A" Circuit Bank 1 or Single Sensor
C0057 — ISO/SAE Reserved

Good customer attempted to replace timing belt and came to us because car was running rough. Code P0340 set immediately after belt replacement and had never been on before. He replaced cam sensor with no improvement. We found his cam timing was off two teeth on right cam, one tooth on left. After resetting timing and clearing codes the engine runs smoothly, but P0340 resets immediately on start up with the cruise light flashing. Pinned out cam & crank wiring to ECM- OK. Found connector at crank sensor broken- replaced crank sensor and connector. Installed Subaru cam sensor- all without improvement. I'm a newbie with a scope, but I did get a waveform out of both the cam and crank sensor signals at the ECM. Watched Bernie Thompson's case study- cams have not been replaced and fault occurred immediately after belt replacement. Any ideas would be greatly appreciated! Thanks!

Cameron Technician

I had one of these 2 years ago with the same problem. Turns out that there were marks that looked like timing marks but were in fact not. I didn't think a mistake like that could be made but you may want to pull the covers again for a final look. I believe the mark used (by the previous belt installer) for timing was a triangle but infact it was supposed to be a rectangular dash. Anyway, point…

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Steven Mechanic

If cam sprock removed n mixed up could cause this 3 cam sensor steps on one s 2 cam sensor steps on other by steps I mean notches for sensor to read

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Brian Owner/Technician

Recheck timing marks. Pulleys have multiple marks. Also make sure all the slack from T-belt is on the tensioner side before release. There is enough slack for pulley to rotate after release

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Eric Owner/Technician

Upload your scope capture for us to see. Single or double overhead cam engine? Were the cam and/or crank pulleys removed at any time?

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Benjamin Owner/Technician

The Bernie video you are referring to, is that the one where the cams were magnetized? Do you suspect he stored timing components in magnet trays? In that video I saw he used an iPhone app for checking magnetism as well as other tooling, but what let him to it was the cam signals where reversing polarity at a higher rpm.

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Robert Owner/Technician
New York
Robert Resolution

After rechecking timing and wiring, replacing sensors, and checking waveforms, we finally fixed this with a new Subaru left cam sprocket. That immediately corrected the P0340 issue- apparently the sprocket had come in contact with a magnetic source when the customer first replaced the t belt. The replacement sprocket from Subaru had two single sensor nodes spaced at 90 degrees. The original had…

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