P0311 Code – Meaning, Causes, Symptoms (& How To Fix)

What does the P0311 code mean? Get an understanding of the causes and symptoms of this trouble code and learn how to fix it.

P0311 Trouble Code

If you have scanned your engine computer to see what’s causing trouble and found the P0311 code, you might wonder what is going on and how to fix it. Thankfully, it doesn’t take a lot of troubleshooting to get to the bottom of this issue.

In this guide, we look at the meanings of the P0311 trouble code. We also show you what might happen when this occurs and evaluate how to repair it. 

Code P0311 Definition

P0311 – Cylinder #11 Misfire Detected

What Does the P0311 Code Mean?

P0311 DTC means that there’s an engine misfire in cylinder 11. The Powertrain Control Module (PCM) detects that a misfiring is occurring in the 11th cylinder in the car motor, thereby alerting the engine to set this trouble code. It’s a generic code, applying to all OBD-II equipped models.

While the P0311 trouble code might be considered generic, the repairs could depend on the make and model you drive. If there are multiple misfires occurring, you could also see the P0300 code together with other related codes indicating problems with other cylinders as well. 

P0311 Trouble Code Symptoms

If one of the engine cylinders is misfiring, you should notice some performance issues. Additionally, the Check Engine Light will come on when the code is set, alerting you to the problem. 

Here are some of the top symptoms you’ll notice with the P0311 DTC.

Causes of the P0311 Code

When the car engine is misfiring, it can be caused by a number of problems. In some cases, the issues could stem from the ignition system, but it’s also possible that something has failed with the fuel system.

Here are some of the most common causes of the P0311 trouble code.

How Serious is the P0311 Code?

Severe – The P0311 DTC is considered one that should be taken seriously. Driving with an engine misfire can become dangerous, especially if the car starts to stall in the middle of the road. If the engine stalls, it might be difficult to get it started back up, leaving you in a hazardous situation.

It’s important to have the P0311 trouble code examined as soon as possible. Running the engine with a misfire can also cause other engine troubles that will add to the repair bill. Plus, if the car breaks down, you might have to pay for a tow truck. 

What Repairs Can Fix the P0311 Code?

You must perform a complete diagnosis before you attempt any repairs. Otherwise, you could spend unnecessary money on parts that aren’t needed.

Based on what fails most often, here are a few of the fixes that might be in order.

  • Replace spark plug
  • Replace ignition coil/wires
  • Install a new fuel injector
  • Fix leaking valve
  • Fix vacuum leak
  • Replace piston ring
  • Repair leaking head gasket
  • Replace computer module

Common P0311 Diagnosis Mistakes

Most commonly, the spark plugs, ignition coils, wires or coil pack is going to be to blame for the misfire. However, you should never assume that’s the problem without first performing the diagnostic steps we outline. You want to perform a visual check of the plugs, wires, coils, and coil pack before replacing it. 

If these parts look okay, you need to move on to other parts that could be causing the trouble, such as the fuel injectors or valves. You also want to perform a compression test. Additionally, if there are any other trouble codes present, these might help you narrow down what’s going on. 

How to Diagnose the P0311 Trouble Code

As a professional mechanic, you want to follow a laid-out plan when diagnosing the P0311 code. Gathering the code from the scanner is just the first step of figuring out what’s wrong. With the right steps, you will have a definitive answer to the problem.

Here are the most common diagnostic steps for the P0311 DTC.

  1. Collect the trouble codes with your OBD-II scanner and use freeze frame data to see what’s going on. Continue the troubleshooting based on the other trouble codes you may find.
  2. Reset the codes.
  3. Test drive the vehicle to see which codes come back.
  4. Inspect the spark plug, ignition coil, wire or coil pack on cylinder 11 to see if it is damaged or worn. Replace if necessary. You can try to move over the spark plug and ignition coil to another cylinder to see if you get a trouble code on the other cylinder instead – if so replace the faulty spark plugs and ignition coil.
  5. Check the intake system for a vacuum leak.
  6. If this isn’t the problem or the code doesn’t go away, you will need to inspect the fuel injectors. 
  7. If you have an older car, you might also need to look at the distributor cap and the ignition cables. 
  8. Beyond this, a compression test of cylinder 11 will be needed. 
  9. Check the camshaft timing and inspect the timing belt or shaft if necessary.
  10. If nothing else can be found with the diagnostics, you might find the PCM is bad and needs to be replaced. However, with this problem, you’ll likely see other false codes or problems. 

Estimated Cost of Repair

Depending on what’s causing the problem, you are looking at a varying amount of repair costs. Some issues are going to cost far less than others to fix. Below we list a few of the most common repairs and the average cost for parts and labor.

  • Replace spark plug – $40-$350
  • Replace ignition coils/wires – $75-$400
  • Install a new fuel injector – $200-$500
  • Fix leaking valve – $500-$2,500
  • Replace piston ring – $1,000-$5,000
  • Repair leaking head gasket – $1,500-$3,000
  • Replace computer module – $750-$3,500

Mechanics Tips about the P0311 Code

If you find that the cylinder 11 spark plug is causing the p0311 code, you could simply replace that plug and move on. However, it’s always a better idea to replace all of the plugs at the same time. If one is failing, the others are probably shortly behind. Plus, by replacing the spark plugs all at once, you can stay on a recommended maintenance schedule with ease. 

You also want to make sure that the spark plugs are adequately gapped. A gap that is too small or too wide can easily lead to a misfire. Use a spark plug gap tool to ensure the space matches the manufacturer’s specs.

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