Error P0311 – how to fix?

Code definition P0311

P0311 is set when the powertrain control module (PCM) detects a misfire in engine cylinder 11. When this happens, the engine indicator light or the MIL (malfunction indicator light) will illuminate and will remain on until the problem is resolved.

What does the code P0311 mean

A misfire in a vehicle’s engine is simply a lack of combustion which has several potential causes. The P0311 code is a means for the PCM to remember the fact that cylinder 11 has failed. Based on this code, the mechanic can determine the cause and appropriate repairs to prevent further cylinder failure in the future.

What causes the code P0311?

• As code P0311 is specific to cylinder 11, all causes and repairs will be related to that cylinder. Some of the problems that can occur with cylinder 11 and its components are
• Defective spark plug
• open or shorted fuel injector
• Fuel injector clogged or damaged
• Defective ignition coil
• Bad electrical connection to the fuel injector
• Ignition coil wiring harness is open or shorted
• Insufficient cylinder pressure
• Incorrect fuel pressure
• Intake air leak

What are the symptoms of the P0311 code?

An improperly lit cylinder does not cause many symptoms, but you may notice the vehicle vibrating at idle when the ignition is not working. Fuel efficiency can also suffer, as can the car’s performance on the road. One constant symptom, of course, will be an illuminated Check Engine or MIL light.

How can a mechanic diagnose the P0311 code?

After using the OBD-II scanner to detect the P0311 code, the mechanic will know which cylinder is failing and can take steps to diagnose the problem. One of the first diagnostic steps is to replace the ignition elements between cylinder 11 and one of the good cylinders. After replacing the components, the mechanic clears the code and restarts the vehicle to see if the ignition fault code has been transferred to the new cylinder. If so, one or more components are problematic and must be repaired or replaced.

If the component change leads to the same P0311 code then the problem may be a compression problem. The most likely causes are problems with the exhaust valves or a leak in the head gasket. The mechanic will look for coolant leaks or an overheating engine as potential indicators of a problem with the head gasket.

The most common errors when diagnosing the P0311 code

The assumption that the ignition elements in cylinder 11 are the problem and have them replaced before checking with a good cylinder is a common problem. While these components are the most likely cause of the problem, it’s best to do a thorough diagnosis and determine what exactly the problem is before drawing a (potentially costly) conclusion.

How serious is the P0311 code?

In some cases, the P0311 code will not be very serious and will only be noticed by an illuminated Check Engine light and a noticeable vibration at idle. However, if the problem of one cylinder is left alone, it can become a much bigger problem. That is why it is so important to check the vehicle as soon as possible and make the appropriate repairs.

What repairs can fix the P0311 code?

In most cases, an incorrectly igniting cylinder can be repaired by replacing some or all of the ignition components, such as

1. Spark plug
2. Fuel injector
3. The ignition coil
4. Ignition coil wiring
5. If the problem is not caused by the ignition components, it can probably be corrected by repairing or replacing the leaking cylinder head gasket or exhaust valve.

Additional considerations to consider the P0311 code

If the misfire on cylinder 11 does not affect the operation of the vehicle, it may be tempted to omit this code. Note, however, that your vehicle cannot pass the OBD-II Emissions Tests while the Check Engine Light or MIL is illuminated.