Definition of error code P0312
The definition of error code P0312 is that cylinder #12 has failed.
What does code P0312 mean
The operation of any automobile engine is based on the use of cylinders. Each of these cylinders requires a spark plug, which is located at the top of the cylinder. These spark plugs fire one by one to ignite the mixture of air and fuel needed to run the vehicle’s engine.
Once ignited, the mixture produces power, which then drives the crankshaft. The cylinders rotate to regulate the speed of the crankshaft. Sequential ignition allows the crankshaft to turn smoothly and the vehicle to move smoothly on the road.
Sometimes there is a fire break in one of the cylinders. When this happens, the number of revolutions per minute on the crankshaft may increase or decrease. There is a predetermined range of revs that the manufacturer has deemed appropriate for the vehicle. If, as a result of misfiring, the crankshaft reaches a speed 2% above or below this range, the PCM (powertrain control module) will register a fault code. On a 12-cylinder engine, when the cylinder responsible for the misfire is #12, the code that is recorded is P0312.
What causes code P0312?
- The simplest diagnosis and by far the most common reason for storing P0312 is that something is wrong with your spark plug. It may be completely broken or it may be contaminated in some way.
- It could also be a lack of compression in that cylinder. This would lead to a lack of revs, because there wouldn’t be as much power.
Other common causes include
- Burnt valves
- Defective fuel injectors
- Bad ignition timing
- Vacuum leak
- Crankshaft sensor defective
- Camshaft sensor defective
- Defective air mass flow (MAF) sensor
- Problems with the catalytic converter
- Although this rarely happens, it is possible that the PCM is malfunctioning. However, if this were the case, the following symptoms would most likely not occur.
What are the symptoms of the P0312 code?
As with many trouble codes, P0312 will cause the Check Engine light to come on. If the rpm increases above or below the range by 10%, the Check Engine light will come on. However, the big difference is that with this code it is possible to make the light blink. This happens when the RPM is outside the allowed range of 10%. This means that cylinder #12 has no ignition because it is not getting a spark from its spark plug – a much more serious problem.
Other symptoms include:
- The engine has difficulty starting.
- Engine hesitates or runs unevenly
- Difficulty in accelerating the engine
How can a mechanic diagnose the P0312 code?
The mechanic will start by using an OBD-II scanner to find out what fault codes were recorded by the PCM. He will then inspect the engine components. This would include cylinder #12, its spark plug, wiring harness and connectors. After the necessary repairs and replacements are made, you will test the unit while the scanner is connected and running.
The most common errors when diagnosing the P0312 code
The most common error is when a mechanic simply replaces the spark plug and assumes that this is sufficient. As can be inferred from the above, the P0312 code can also represent a number of other problems, so even if the spark plug was defective, a thorough diagnosis should be performed.
How serious is the P0312 code?
This is definitely a code that should be taken seriously. Some of the potential symptoms listed above can make driving dangerous. Even if the dangerous symptoms are not present, it will still be difficult to drive with this code.
What repairs can repair a P0312 code?
The following repairs are usually sufficient:
- Replacement of a faulty spark plug.
- Replacement of damaged spark plug wires
- Repairing damaged engine components
- Repair or replace damaged cylinder head gaskets
- Replacement of burnt valves
- At worst, the engine will have to be replaced because the damage to the cylinder is so extensive.
Additional notes for note for code P0312
Always replace the spark plugs in pairs. However, a P0312 code usually means that the rest of the vehicle may also need servicing, so it is probably best to have it done in the near future.
