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05-12-2016, 09:27 PM | #26 |
Scooby Newbie
Member#: 3409
Join Date: Jan 2001
Chapter/Region:
NWIC
Location: Oly
Vehicle:98 My FMIC Is bigger than yours. |
If you can force the failure, do what I said above. Go ahead and try doing a reflash, but if the issue is excessive drag in the compressor, that shouldn't fix anything.
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05-12-2016, 09:45 PM | #27 |
Scooby Specialist
Member#: 139816
Join Date: Feb 2007
Chapter/Region:
Tri-State
Location: NJ
Vehicle:2019 Impreza White |
I think the failure was coincidence since I recall running the defroster and AC before and it didn't trip. I'll try that one last time tomorrow before the reflash.
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05-18-2016, 02:43 PM | #28 |
Scooby Specialist
Member#: 139816
Join Date: Feb 2007
Chapter/Region:
Tri-State
Location: NJ
Vehicle:2019 Impreza White |
changing the ECU didn't do anything. Problem still came back, CEL came on immediately even without the AC on. I'm out of ideas.
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05-19-2016, 12:11 AM | #29 |
Scooby Newbie
Member#: 3409
Join Date: Jan 2001
Chapter/Region:
NWIC
Location: Oly
Vehicle:98 My FMIC Is bigger than yours. |
Are you getting your money back for the ECU?
Are my posts hidden? Did they put the scope on it and monitor the cam signal? Did they actually do the resistance checks? How about taking some shielded wire and overlaying the cam position sensor wires to eliminate any hidden harness issues? Did they do a pin tension test on the sensor, joints, and ECU connectors? |
05-19-2016, 12:21 AM | #30 | |
Scooby Specialist
Member#: 139816
Join Date: Feb 2007
Chapter/Region:
Tri-State
Location: NJ
Vehicle:2019 Impreza White |
Quote:
the ECU i purchased from a fellow member here, so ill probably resell it as i bought it only because the dealer was extremely confident that was the issue. the dealer checked all the wiring for beaks and shorts and found none. they tested all wiring from the sensor to the ECU and found no issues with them. all resistance measurements were within spec, and I've seen no damage to any tires, the harness or clips. the dealer was able to test both new and old sensors and verified both worked without issue. i assume they used an oscilloscope, but who knows. after reading another thread, i even tried wrapping the CMP with foil to shield it with no avail. after doing more research for the past 5 hours, it appears two fellow members here have had my exact issue (specifically being able to trigger the fault with turning the AC on). both of their final solutions were to replace the alternator due to a bad diode or voltage regulator. apparently it feeds noisy signals into the harness, triggering the CMP. there are tons of threads on other forums, specifically prone on Mustangs, but also other modular ford engines that also have this alternator noise issue. since my symptoms seem to fit those, as opposed to others (no start, rough start and bad idle, which would indicate bad sensor, bad timing or other mechanical issue), my assumption is my 14 year old alternator is failing. i measured its voltage and its 14.2 while idle, 12.5 under load of the lights, AC defroster and radio on. but apparently the voltage can test well, its the noise that triggers it. i will have the alternator tomorrow and install it. |
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05-19-2016, 11:36 PM | #31 |
Scooby Specialist
Member#: 139816
Join Date: Feb 2007
Chapter/Region:
Tri-State
Location: NJ
Vehicle:2019 Impreza White |
so i unplugged the alternator and reset the ECU. started the car up and....no CEL. plugged the alternator back in and sure enough, immediately got the CEL (P0340).
so i swapped out the alternator for a new one, started the car up and no CEL. voltage at the alternator and battery under load is reading 14.2 volts. so in the end, it appears that indeed, a bad alternator can truly cause the P0340 code. apparently a bad diode or voltage regulator sends a noisy signal through the harness and the cam sensor reads this as a fault. so anyone experiencing this code and has the primary symptoms of momentary rough idle especially when the AC is turned on, please check the alternator. it may appear to be sending proper voltage or even pass testing, however internally its faulty and is tripping the CMP. for people who have a no start situation with this code, your actual sensor may be bad, faulty wiring, bad ECU or skipped timing. |
05-20-2016, 12:27 AM | #32 |
Scooby Newbie
Member#: 3409
Join Date: Jan 2001
Chapter/Region:
NWIC
Location: Oly
Vehicle:98 My FMIC Is bigger than yours. |
*golfclap*
A scope would most likely see the noise, but figuring out where it came from would take some additional effort. I have replaced (and seen others also) alternators in relatively new (<1 year old) cars due to triggering random codes. I think they were P0300 misfire codes if memory serves me correctly, but techline said it was due to the internal resistance causing enough drag that it slowed the engine just right for a misfire code. |
05-20-2016, 12:34 AM | #33 |
Scooby Specialist
Member#: 139816
Join Date: Feb 2007
Chapter/Region:
Tri-State
Location: NJ
Vehicle:2019 Impreza White |
they scoped the sensors, which showed no issues. getting the engine to rough idle when the AC was on was come and go. it wasn't every startup, and very rarely while under way. earlier today, upon first startup of the day, it rough idled when i turned the AC on, but the ECU quickly compensated by increasing the RPMs and it leveled out. sure the code was there, but the actual fluctuating rough running wasn't always there for them to read. in fact, i spoke with them today and they stated even though they witnessed the rough running while i was there, they were unable to recreate it while it was in the shop and scoped. i knew my issue was not a typical P0340 issue, only two other NASIOC members noted their issue with the AC being a primary symptom and i was the third. however, this exact issue is HUGE among the mustang forums, which further proved my theory.
in the end, my research on these forums and others prevailed. i took some unfortunate shots in the dark with replacing the ECU and sensor, but that and the dealer were at least able to rule out everything else, helping me narrow in on the alternator. |
05-20-2016, 09:03 PM | #34 |
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Member#: 444025
Join Date: Apr 2016
Chapter/Region:
Tri-State
Location: NJ
Vehicle:2002 WRX SRP |
Good job Zampi!!!! So proud of you lol
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05-21-2016, 01:33 AM | #35 |
Scooby Specialist
Member#: 139816
Join Date: Feb 2007
Chapter/Region:
Tri-State
Location: NJ
Vehicle:2019 Impreza White |
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04-05-2018, 02:44 AM | #36 | |
Scooby Specialist
Member#: 459287
Join Date: Dec 2016
Chapter/Region:
VIC
Location: Vancouver BC Canada
Vehicle:1998 JDM Impreza STi V4 GF8 White |
Good job!
Quote:
So many times the final answer is never posted in a thread, which renders the thread basically useless. However, this thread will continue to help people for years! |
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04-05-2018, 08:33 AM | #37 | |
Scooby Specialist
Member#: 139816
Join Date: Feb 2007
Chapter/Region:
Tri-State
Location: NJ
Vehicle:2019 Impreza White |
Quote:
You’re welcome. Let us know what the issue ends up being. |
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08-16-2018, 12:46 PM | #38 |
Scooby Newbie
Member#: 490239
Join Date: Aug 2018
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Hi I have a 01 WRX sedan engine light came on IV obd it it's saying camshaft position sensor problem if I turn off the car for a little bit it will turn off but as soon as I take off fast it will turn on again iv change the belt s and fully serviced it can anyone help me with it
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08-16-2018, 01:27 PM | #39 |
Scooby Specialist
Member#: 139816
Join Date: Feb 2007
Chapter/Region:
Tri-State
Location: NJ
Vehicle:2019 Impreza White |
Mine was caused by a bad alternator. Did you test that yet?
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04-04-2020, 01:41 AM | #40 | |
Scooby Newbie
Member#: 477300
Join Date: Nov 2017
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Quote:
Thank you so much |
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09-26-2020, 10:32 PM | #41 |
Scooby Newbie
Member#: 6845
Join Date: May 2001
Location: Bay Area, CA
Vehicle:1999 Outback Sport White/Titanium |
As I’ve posted on other threads, the plug ends on the harness are the exact same, even in color, for the #4 injector and the cam position sensor. The way the wires come out of the harness can lead a person to believe the two injector wires are a couple with the cam sensor plug is the outlier, which is wrong.
Swapping the plugs immediately cleared my code and the car started and idled normally and not in failsafe mode. |
10-09-2020, 07:31 AM | #42 |
Scooby Newbie
Member#: 328158
Join Date: Aug 2012
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My P0340 also ended up being the alternator. 2002 WRX with 170k miles. With an OBD2 bluetooth reader, I was able to monitor the voltage and when the car would in motion, the voltage would be fluctuating between 11 to 13 amps. Specially coming to a stop sign or stop light, the voltage would drop at around 11. The car never stalled or gave me other issues besides having this CEL on. After replacing the alternator, the CEL completely went away and I'm at 180k now with no further issues.
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03-16-2023, 06:15 PM | #43 |
Scooby Newbie
Member#: 533572
Join Date: Mar 2023
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06 Outback XT 217k Miles
I stumbled upon this thread from a google search. Made an account to reply. I have had 2 sensors fail on me. On my 3rd sensor. My mechanic tested all my wiring for voltage, and resistance. Battery tested out fine. Told them to blasting the AC to see if it triggers the code.
If this works you gentlemen are legends and saved me thousands of dollars on a new car. |
03-16-2023, 06:50 PM | #44 | |
Scooby Specialist
Member#: 139816
Join Date: Feb 2007
Chapter/Region:
Tri-State
Location: NJ
Vehicle:2019 Impreza White |
Quote:
But yes, in the end it was just an alternator |
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04-29-2023, 07:33 PM | #45 |
Scooby Newbie
Member#: 521413
Join Date: Jan 2021
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If it helps at all . . . I fought this EXACT issue in my 2006 2.5i for 3 months. 1st cam sensor. no change. Batt disconnect delayed the eventual return of the p0340. Finally . . . the starter started stated spinning out without engaging the flywheel so I replaced it. NOW it cranks much faster & the p0340 has been gone for a year
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11-13-2023, 11:09 AM | #46 |
Scooby Newbie
Member#: 187725
Join Date: Aug 2008
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P0340 code
I started having this CEL code P0340 about a week ago, same time I noticed a toonie size hole in exhaust pipe right near muffler.
Same pattern 1. START car stutters.. 2. CEL P0340 ON, but car idles ok, runs ok...no other sysptoms observed yet after some time 3. Start car CEL OFF by itself. Can exhaust hole cause P0340 code? UPDATE: car stalled at stop.. Sensor covered in oil is that normal? see Video link below I was told to just replaced camshaft position sensor https://youtube.com/shorts/rF1S1Zm304k?feature=share Last edited by zoso0; 11-20-2023 at 11:04 AM. Reason: update added video link |
12-13-2023, 01:09 AM | #47 |
Scooby Newbie
Member#: 536354
Join Date: Dec 2023
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Im having the same problem with my 2018 subaru wrx check engine light on and p0340 and p0341 showing. Brought it to the shop and they found nothing wrong with it cleared the code but came back on after alittle over a day. Car starts easy runs and drives fine.
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01-27-2024, 07:23 PM | #48 |
Scooby Newbie
Member#: 344749
Join Date: Jan 2013
Chapter/Region:
NWIC
Location: Portland, OR
Vehicle:2013 WRX Premium Cayenne Red |
2005 Forester XT (5MT) that I just bought. 190,000 miles on it.
Ran great for the last 90 miles. Went to move it today, didn't want to start, rough idle, P0340. Cleared code, disconnected battery, still P0340. Glad this thread is here as a guide. Wish me luck. |
01-27-2024, 07:36 PM | #49 |
Scooby Newbie
Member#: 521413
Join Date: Jan 2021
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How does it crank when this happens ? It makes sense that a slow cranking rpm can create this symptom & code, as cam speed is 1/2 of crankshaft rpm. Possibly the result of a failing/lazy starter, as it was in my case. Over time as the starter gets a little tired, its difficult to notice as the change is gradual. When I first cranked it up after the starter replacement, the difference in cranking was insatntly noticble. Its soo much faster & doesnt seem labored as before. Worth a try . . . Also a weak battery/lazy, failing alternator or poor cable connection could contribute to this
Last edited by TALONTRAX; 01-27-2024 at 07:47 PM. |
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