1999 BMW 740il misfires on start up. Idles rough and stalls in reverse. Doesn't start up at all. I've changed the camshaft position sensor on the driver side with after market sensor. I even bought an

P0343 - Camshaft Position Sensor 'A' Circuit High InputI'm surprised Autozone didn't give you a printout of the possible causes or tell you what they were. These are possible causes but it could also be the wiring in the system too.


- Faulty Camshaft Position Sensor
- Camshaft Position Sensor harness is open or shorted
- Camshaft Position Sensor circuit poor electrical connection
- Faulty starter motor
- Starting system circuit
- Dead (Weak) battery

DTC P0340 - Camshaft Position Sensor Circuit Malfunction
This indicates that a problem was detected in the camshaft position sensor circuit. Since it says circuit, that means the problem could lie in any part of the circuit - the sensor itself, the wiring, or the PCM. Don't just replace the CPS (camshaft position sensor) and think that will definitely fix it.

Symptoms can include:
Hard starting or no start
Rough running / misfiring
Loss of engine power

A code P0340 could mean one or more of the following has happened:
a wire or connector in the circuit could be grounded/shorted/broken
the camshaft position sensor may have failed
the PCM may have failed
there exists an open circuit
the crankshaft position sensor may have failed

Possible Solutions: With a P0340 OBD-II trouble code, diagnosis can be tricky at times. Here are some things to try:
Visually inspect all the wiring and connectors in the circuit
Check for continuity in the circuit wiring
Check the operation (voltage) of the camshaft position sensor
Replace the camshaft position sensor as required
Check the crankshaft position circuit as well
Replace circuit wiring and/or connectors as required
Diagnose/replace the PCM as required


Hope this helps; also keep in mind that your feedback is important and I'll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using Fixya, and have a nice day

look for vacuum leaks

P0316 crankshaft position sensor, camshaft position sensor, or a wiring issue. Since this code indicates a start up misfire, pay attention to items which may expand or contract when cold (if the code sets when the engine is cold), or hot (if the code sets on a hot restart).

If you have other misfire codes that pertain to individual cylinders, you should attend to them first P1151 has a huge list of things that it can be, But included in that list is the camshaft position sensor , po1131 is the same thing, all building up to your car is running lean , so I'd do the sensor (cam) and check timing,,

• There are two Camshaft position sensors. The one this is for is the one by the oil dipstick on the LH side of the engine. If you replaced the other you need to replace this one as well. Both are recommended, in other words when changing one it is recommended to change the other as well.
• If you have any further questions or comments please feel free to ask and thank you for using FixYa.

• That being said I sat in a chat and waited for a response from you for 12 minutes. I hope this answers your question.

Regards, Tony

Camshaft Position Sensor-On top of engine Operation The Engine Management System (EMS) uses the camshaft position sensor to manage sequential fuel injection and as part of misfire diagnosis. The EMS constantly monitors the number of pulses on the signal circuit. The EMS compares the number of camshaft sensor reference pulses and the number of crankshaft position sensor reference pulses received. If the EMS receives an incorrect number of pulses, Diagnostic Trouble Codes (DTCs) should be stored in the EMS. Some engine management systems will then default to multi-port or "gang-fire" injector operation. The camshaft position sensor signal is required to sequence the injector operation to the proper cylinder timing. If the camshaft position sensor or circuit is faulty, most engines will start. However, the EMS misfire diagnostic will likely be affected.
The following symptoms can be caused by an intermittent wiring connections or faulty signal to the EMS.
Related Symptoms

• Extended crank time with a cold engine
• Intermittent rough running
• Unstable idle
• Bucking
• Hesitation
• Stumble
• Chuggle
• Poor fuel economy
• Stalling on acceleration

1391 is the intermittent loss of either the Camshaft Position Sensor or the Crankshaft Position Sensor.

Is your engine running rough, sputtering; or has it recently stalled out? If so then either one of these Sensors could be failing. However if your engine stalled-out or sputtered, this Code will appear. IF there are no other Codes (like a Misfire Code) then the Crankshaft Position Sensor would be the 1st Sensor to replace, then (2nd) the Camshaft Position Sensor.

Helpful TIP: IF you replace either the Sensor MAKE SURE you use approved replacement OEM parts. Some after market Sensors have been found to be faulty and/or will fail.

Let me know if this helped, or if you have additional information or questions. Feel Free to contact me at FixYa.com!

well. if it idles rough without a load and then worse with a load i would try changing spark plugs and ign. wires. also try pulling out your idle air control valve and clean it out. if that doesnt work look up testing for your throttle position sensor. check for worn vacuum lines and check for vacuum leaks. if it runs rough throughout driving it will be ign. or fuel delivery. get some injector cleaner and throw it in your tank. if non of this works then your in the same spot as me bud. oh and check your camshaft position and crankshaft position sensor and also your speed sensor.
good luck to ya bra

Crankshaft and Camshaft Position Sensors Camshaft Position Sensor Engine timing is determined from the relationship between the crankshaft and camshaft. This relationship is maintained by a timing chain or timing belt. The Engine Management System does not control engine timing but it does monitor the relative position and speed of these shafts by monitoring signals generated by sensors. The Engine Management System (EMS) uses signals generated by the camshaft position sensor to synchronize fuel injection to the valve sequence and for the on-board diagnostic procedure for misfire detection. The EMS energizes the injector at or near the time the intake valve opens. For misfire diagnosis, the EMS compares the number of camshaft sensor reference pulses and the number of crankshaft position sensor reference pulses received. If the EMS receives an incorrect number of pulses Diagnostic Trouble Codes (DTC’s) should be stored in the EMS.
If the camshaft position sensor or circuit is faulty most engines will start. Some engine management systems will then default to a pre-programmed injector firing sequence. All injectors may be energized simultaneously or all of the injectors on one bank may be energized at the same time. If the CMP data is required for misfire detection and reliable CMP data is not present misfire detection would probably be suspended.
Related Symptoms The following symptoms can be caused by an intermittent wiring connection or faulty signal to the EMS:

• Extended crank time with a cold engine
• Intermittent rough running
• Unstable idle
• Bucking
• Hesitation
• Stumble
• Chuggle
• Poor fuel economy
• Stalling on acceleration

Crankshaft Position Sensor Engine speed is a very important input to the Engine Management System (EMS). Crankshaft speed and position are the basis for many calculations made by the computer. Crankshaft position values are transmitted to the computer by pickup coils also known as Permanent Magnet (P/M) generators, hall-effect sensors or optical sensors. The Crankshaft Position Sensor (CKP) also known as engine speed sensor is located in close proximity to the crankshaft.
In addition the EMS uses minute variations in the CKP sensor data to determine engine misfire. The EMS uses this information in conjunction with the camshaft position sensor to perform misfire diagnostics.
Related Symptoms: No Start/Intermittent Start Condition – Can be caused by a faulty crankshaft position sensor due to loose connections, bad grounds, high resistance in the circuit, or opens in the circuit

a picture is worth 1000 words if ya need more help let me know