BMW diagnostic code P1345 indicates a misfire on cylinder 2 with fuel cut-off. There are many different causes of misfires on BMW engines. Really an engine for that matter. Fortunately, the fix for P1345 is typically simple and not something that's going to break your bank. Let's jump in and discuss BMW DTC P1345.
Cylinder 2 Misfire - What is it?
A misfire happens when the cylinder fails to fire at all or fails to fire at the proper time. This occurs when there is a lack of fuel, oxygen, or a spark to ignite the air/fuel mixture. When one of the three pieces are missing or lacking it can result in engine misfires. We'll leave it at that to avoid getting overly technical.
Again P1345 indicates a misfire on cylinder 2. You may also receive misfire faults on multiple cylinders. This is an important aspect to tracking down the actual issue at hand. Several misfires indicate a broader problem. A misfire isolated to cylinder 2 indicates an issue with that cylinder specifically. We'll cover all of this in the next section.
P1345 Engine Fault Code Causes
A few causes of BMW P1345 fault code include:
- Spark plug
- Ignition coil
- Fuel injector
- Fuel pump(s)
- Intake vacuum leak
- Camshaft position sensor
- Ignition coil harness or circuit
The points in bold are typically the most frequent causes of BMW misfires and P1345 codes. However, some of it comes down to a model by model basis. The N54 engine, for example, runs into common problems with the fuel pumps and injectors.
You may also get other fault codes. For example, if it's something fuel related like the injectors or fuel pump you'll probably get a code suggesting your BMW is running lean. Let's break down each of the above causes further.
P1345 Faulty Plug, Coil, or Injector
These are the problems that generally cause isolation to cylinder #2 alone. Each cylinder uses its own spark plug, ignition coil, and fuel injector. Spark plugs and ignition coils are by far the two most common causes. They're both standard wear and tear items that become less effective with age and mileage. Fuel injectors usually last the life of the vehicle so we'll skip those for a second. To diagnose the P1345 code back to spark plugs or coils you can try this:
- Swap ignition coil #2 with the ignition coil from another cylinder
- Drive for a little and see if the misfire follows to the new cylinder
- If not, swap spark plug #2 with a spark plug from another cylinder
- Drive and check if the misfire follows to the new cylinder
If the misfire follows the spark plug or ignition coil to the new cylinder you've found your issue. You can start with swapping the spark plugs if you choose. However, the coil is typically easiest since it sits on top. Lastly, you may try swapping fuel injectors but it's a pretty rare failure.
If it's your spark plug or ignition coil causing the issue we highly recommend replacing all of them. They rarely fail suddenly but they wear down over time. If one gives out then the rest may be on their way out, too.
Other Causes of P1345 & Fixes
Fuel pump, vacuum, cam position sensor, or ignition coil wiring harness problems may also cause BMW fault code P1345. These causes will typically be accompanied by additional fault codes. They're generally not isolated to one cylinder. As such, you may receive fault codes for misfires across multiple cylinders.
Look for the camshaft position sensor to be one of the more common P1345 causes. This is especially true on older BMW's as these sensors tend to go bad with older age.
Symptoms Alongside BMW P1345 Fault
As a final note there are a few symptoms you may notice alongside a P1345 fault code. These include:
- Rough idle
- Power loss
- Long cold start cranking
- Service Engine Soon (SES) light
Most of these symptoms go hand in hand with engine misfires. The severity of symptoms may help point you in the right direction. For example, spark plugs and ignition coils rarely fail suddenly. It may only be misfiring occasionally under heavy throttle with faulty plugs and/or coils. Fuel flow or camshaft position sensor problems are more likely to have severe symptoms, especially at idle.