2004 G35X 217K
About a couple of weeks ago, my car developed this new quirk. Sometimes, at random, when I try to start it, it cranks fine but doesn't fire. That seems odd so I used my remote to lock and then unlock the car and it started just fine as before. It has done the same thing a few times since. Today, I turned the engine off for about 2 minutes.. and when I tried to restart it.. it cranked but no start. I tried the lock and unlock with the remote trick and it didn't work. After repeating the process a few more times, it fired as before. Obviously there is something amiss. I'm thinking it's in the lockout system but don't know if it's the key or what. The key I'm using is a dealer replacement purchased about 2 years ago. I don't have another to try it with. Any suggestions would be greatly appreciated.
I just pulled the codes and got
P0340 Camshaft Position Sensor "A" Circuit
U1000 Controller Area Network Line Malfunction
P0462, P0463 Fuel Level Sensor A

Not sure if any of these could be it. Any advice would be appreciated.

 

If your security light (red key on the combo meter) is on when you're getting crank no start behavior, it's the immobilizer that is keeping the engine from firing. Certain kinds of U1000 can cause crank no start but should also come with other behavior like your fans running immediately when you turn the key to accessory (fail safe mode because the ecm can't read the coolant temp so it has no idea how hot the engine is so runs the fans just in case). If the ECM or BCM is issuing the U1000 (no CAN comm), the immobilizer can't get the info it needs to confirm you have the authorized key in the car so it won't enable starting.

I think bad cam position sensor can cause no start also. The car doesn't know when to fire because it doesn't know where the cam is. Clear the codes, when you get the crank no start, read them again and see what comes back. I don't think the cam position code should be related to the CAN comm U1000 code at all.

I don't think the fuel level code can cause any intermittent starting issue. If you don't have an accurate fuel gauge and you run out of gas, that can obviously cause crank no start but it won't be intermittent.

 

Thanks.. can you tell me which camshaft position sensor s the "A" Circuit? This looks like a DIY fix but there's two.. guess I should probably replace both just to be on the safe side but it would help if I knew which was which so I could replace the A one first.

 

I searched the forum and seems like P0340 points to the cam sensor on the passenger side. Super strange timing but my 06 X model died on me during my drive home last night and would crank but not restart. It started right up when the tow truck got there though..... It's been having little bursts of ignition cut out the last couple of weeks but hadn't thrown a code so it was just a matter of time. I got a P0335 code so gotta look into the crankshaft sensor this weekend.