I have a 2008 Infiniti M45x with 87k miles. I purchased this vehicle used in January of this year with 83k miles.
The problem: Starting in April, I have had multiple incidents where the engine has stubbled/stuttered sometimes at highway speeds, sometimes when stopped and idling. These episodes are mild (no significant engine bucking) and last for only a second and then everything returns to normal except the Service Engine Soon light comes on as well as the VDC Off and SLIP lights and the Lane Departure Correction icon light. Also, following a stumble/stutter episode, multiple restart attempts are usually necessary to get the engine restarted. The OBD code has consistently been P0340. To date, both cam sensors and the crank sensor have been replaced twice by my local trusted mechanic, the first time with after-market parts and the second time with OEM Nissan parts and still the problem persists.
More data:
The car will always start up when cold and run normally.
If driven only short distances, the engine will operate totally normally and will restart totally normally after being shut down.
The car will need be driven between 30 minutes to several hours before the engine will stumble/stutter.
The stumble/stutter episodes last for no more than one second and occur infrequently (maybe twice on a 6 hour drive for example). When this occurs the tach needle will fluctuate.
The engine has never stalled out on me. So long as the engine is not shut off, it will continue to operate totally normally despite one or more stumble/stutter episodes.
However, once the engine is warm and has experienced a stumble/stutter, even if more than an hour ago, and is then shut off, it takes multiple restart attempts before the engine will catch and then run normally. And there has been one time when it failed to restart following maybe 10 restart attempts in as many minutes. Finally, after about 45 minutes following restart attempts spaced at 10 minute intervals, it did restart and run normally.
When attempting to restart the engine, it cranks strong. When cranking but failing to restart, there are muffled soft booming sounds that I take to be fuel igniting somewhere in the system.
I have only experienced the stumble/stutter when the engine is running at a constant speed anywhere from idle to 2500 rpm highway cruising. I have never felt a stumble or stutter when accelerating. The full engine power is always available.
My perspective is that ambient air temperature (hence engine temperature or under-the-hood temperature) may be a factor. I live in South Carolina and the temps are now starting to get into the 80's. I feel that the stumble/stutter episodes are starting to occur earlier in the engine operation than previously.
I had the battery and alternator checked out by Advance Auto yesterday just for the heck of it. The alternator checked out fine. The battery was showing 550 cold cranking amps, vice its 700 cold cranking amps rating but otherwise checked out okay. Nothing on the battery indicates its age.
My local mechanic is pretty much at a loss for figuring out where to go from here and mentioned a worse case scenario that the problem could be the timing chain or the mechanical part of one or both of the cam positioners that use engine oil pressure to function.
Any thoughts/past experience that might bear on this problem would be most welcome. Thanks.
P0340 Code: Cam & Crank Sensors Replaced - Did not Fix Problem
Re: P0340 Code: Cam & Crank Sensors Replaced - Did not Fix Problem
This is the problem that Costee was pointing to in your other thread. If the mechanic replaced 2 sensors claiming they were both cam sensors, then he has not touched the cam sensor at all. The m45 has one cam sensor located lower on the driver's side. Those easily accessible sensors at the top are not related to p0340.The OBD code has consistently been P0340. To date, both cam sensors and the crank sensor have been replaced twice by my local trusted mechanic, the first time with after-market parts and the second time with OEM Nissan parts and still the problem persists.
Show the shop this link: topic607101.html. Would you get a refund for all the unnecessary sensor work they've charged you for?
It's very likely that your other problems will disappear, but if that's your only code then it's a good starting point, whether it's the sensor or wiring related.
Re: P0340 Code: Cam & Crank Sensors Replaced - Did not Fix Problem
Thanks. I will share this info with the mechanic tomorrow. So far, I paid parts and labor for replacement of two cam sensors with after-market sensors. When that didn't work, the mechanic talked with an Infiniti mechanic he knows who said that Infiniti always replaces the crank sensor whenever they replace cam sensors. My mechanic then replaced the crank sensor with an after-market part and charged me for the part only, no labor. After the after-market parts were replaced with OEM Nissan parts, the mechanic said that I should drive the car for a few days and then we'd talk about the bill. I've always gotten a square shake from this mechanic servicing several cars, so am hopeful I won't get soaked too badly on this repair.
BTW, I tried to add on to my other thread but the NICO site said that not enough time had passed for me to add another post. Strange.
BTW, I tried to add on to my other thread but the NICO site said that not enough time had passed for me to add another post. Strange.
Re: P0340 Code: Cam & Crank Sensors Replaced - Did not Fix Problem
The final chapter, (I hope).
So, after my local mechanic replaced "two cam sensors and the crank sensor" twice - first with aftermarket parts and then with OEM Nissan parts, I still had the problem described. So I then went to the Infiniti dearlership in Columbia, SC, d!ck Smith Infiniti. There, they replaced the "crank position sensor", part # 23731-4M50B 23731M, located on the front of the engine on the driver's side below where the "cam" sensors are. (That is the sensor that prior respondents had pointed to, to their credit and I thanks them.) My problem appears to be solved. I went back to my local mechanic to acquaint him with what the Infiniti dealership had done. And here is where things get very interesting. My local mechanic looked up the Nissan OEM part number for the "crank" sensor he had replaced and it was an EXACT match to the one the dealer had replaced! But my local mechanic said the crank sensor he replaced was on the BACKSIDE of the engine, not the front. While I was there, my local mechanic called the local Infiniti dealership, in this case in Augusta, GA, and inquired into why their prior guidance had not identified the sensor on the front of the engine as the "crank" sensor. From what I took from listening in on this call, the M45, at least for the 2008 model, has TWO identical sensors, with IDENTICAL part numbers, associated with this engine, one on the backside of the engine and one on the front side. I can't say for sure but, I'd give this a 95% chance of being correct.
To his credit, my local mechanic told me there was "no charge" associated for the additional work he had done. Still, I had paid for the replacement of two "cam sensors" and one "crank sensor" at aftermarket prices. There were no further charges for replacing these three parts again with OEM NIssan parts. So, I guess, all in all, I have confidence that my problem was solved and maybe also have some new parts on my car that, technically, were never really needed. But, hey, life has its twists and turns. I'm not pissed at my local mechanic. He did his best with honest intent and then did okay by me regarding his charges for his work. I hope this information proves useful to the next M45 owner with a "P0340" error code.
Good luck and thanks again to all who responded to my posting.
So, after my local mechanic replaced "two cam sensors and the crank sensor" twice - first with aftermarket parts and then with OEM Nissan parts, I still had the problem described. So I then went to the Infiniti dearlership in Columbia, SC, d!ck Smith Infiniti. There, they replaced the "crank position sensor", part # 23731-4M50B 23731M, located on the front of the engine on the driver's side below where the "cam" sensors are. (That is the sensor that prior respondents had pointed to, to their credit and I thanks them.) My problem appears to be solved. I went back to my local mechanic to acquaint him with what the Infiniti dealership had done. And here is where things get very interesting. My local mechanic looked up the Nissan OEM part number for the "crank" sensor he had replaced and it was an EXACT match to the one the dealer had replaced! But my local mechanic said the crank sensor he replaced was on the BACKSIDE of the engine, not the front. While I was there, my local mechanic called the local Infiniti dealership, in this case in Augusta, GA, and inquired into why their prior guidance had not identified the sensor on the front of the engine as the "crank" sensor. From what I took from listening in on this call, the M45, at least for the 2008 model, has TWO identical sensors, with IDENTICAL part numbers, associated with this engine, one on the backside of the engine and one on the front side. I can't say for sure but, I'd give this a 95% chance of being correct.
To his credit, my local mechanic told me there was "no charge" associated for the additional work he had done. Still, I had paid for the replacement of two "cam sensors" and one "crank sensor" at aftermarket prices. There were no further charges for replacing these three parts again with OEM NIssan parts. So, I guess, all in all, I have confidence that my problem was solved and maybe also have some new parts on my car that, technically, were never really needed. But, hey, life has its twists and turns. I'm not pissed at my local mechanic. He did his best with honest intent and then did okay by me regarding his charges for his work. I hope this information proves useful to the next M45 owner with a "P0340" error code.
Good luck and thanks again to all who responded to my posting.