P0343 Code - Meaning, Causes, Symptoms (& How To Fix)

Your car engine uses several sensors to ensure proper operation. When these sensors find a fault, they can trigger the Check Engine Light to let you know something is wrong. If you get the P0343 code with your scanner, you need to know what its meaning is, what causes it, and how to repair it.

I will show you what the P0343 code means and some symptoms your car might be experiencing. This guide also helps you diagnose the fault for a quick repair.

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Code P0343 Definition

P0343 – Camshaft Position Sensor A Circuit High Input (Bank 1)

What Does the P0343 Code Mean?

The P0343 code indicates a high voltage input to the engine control module from camshaft position sensor A. This electromagnetic sensor is fixed on the rotating area of the camshaft to record the position of the teeth.

It monitors every piston stroke, so the engine can adjust the spark and fuel. As the camshaft moves, different gaps occur with the sensor, changing its magnetic field and voltage. If the voltage moves beyond what’s normal, the P0343 code will occur.

P0343 Trouble Code Symptoms

When the CMP isn’t relaying information, you could notice several engine-related symptoms. Most commonly, you will see the Check Engine Light.

Here are all of the symptoms that might occur:

Check Engine Light
Surging or bucking engine
Misfires
Stalling engine
Runs rough intermittently
Engine cranks but doesn’t start

Causes of the P0343 Code

While a faulty camshaft position sensor could be to blame, P0343 is most often caused by an open circuit or short.

Here are a few of the most common causes:

Circuit problem, poor connection or damaged wiring
Faulty CMP sensor
Timing system issue, such as a damaged guide or loose timing chain
Defective PCM, possibly just an update needed
Internal engine defect

How Serious is the P0343 Code?

Medium – The camshaft position sensor is needed to keep the engine running at optimal levels. The computer uses the information received from the sensor to determine proper fuel injection, so when it fails, the performance of the vehicle can suffer.

Even if you aren’t noticing any symptoms at first, they will probably occur as soon as the issue gets worse. Without repairs, the engine could stall, leaving you stranded on the side of the road. It’s best to repair it as soon as you can.

What Repairs Can Fix the P0343 Code?

You should be careful to do proper diagnostics before replacing any parts. Otherwise, you might replace something that isn’t defective at all. Follow the diagnostic steps further below if you aren’t sure what the problem might be.

Here are a few of the possible repairs you may do:

Replace damaged wiring, connector or harness
Replace CMP sensor
Fix the timing system, replace chain or guide
Update PCM
Rebuild engine

Common P0343 Diagnosis Mistakes

The most common mistake when working with the P0343 code is using a cheap replacement sensor. If you don’t put a high-quality part in its place, you could run into more problems later.

It can be tempting to purchase a cheaper sensor, but you will likely pay for it later. Instead, invest the extra money now and save some time doing another installation.

Recommended Tools for Diagnosis

How to Diagnose the P0343 Trouble Code

Here are the steps a professional mechanic would take to diagnose the P0343 trouble code.

Start by checking the condition of the battery. Whenever you deal with voltage issues, start with the charge – although this probably isn’t the problem.
Clear the engine codes and drive the car. If the Check Engine Light returns, run the scanner again.
Inspect the wiring, harness and connectors to the sensor. If you notice any dirt or corrosion, clean it off. If the wiring is damaged, replace it.
Remove the sensor and inspect it. If there is oil on it, clean it off and reinstall it.
Check the sensor’s internal resistance and compare it with the manufacturer’s specs. If the values are off, you need to replace the sensor.
Inspect the timing system and replace any worn parts.
If all else fails, you might need to update the PCM.
Otherwise, there could be internal engine damage, requiring a rebuild. However, there are normally other codes occurring with major engine damage.

Estimated Cost of Repair

All repair costs are dependent on whether you can replace the part yourself and where you take it for labor. Here are some estimates you might consider.

Replace damaged wiring, connector or harness – $5-$500
Replace CMP sensor – $175-$250
Fix timing system, replace chain or guide – $300-$1,500
Update PCM – $150-$300
Rebuild engine – $500-$3,000

Mechanics Tips about the P0343 Code

If the camshaft position sensor has failed, it could be due to an oil leak. If oil contaminates the sensor, it could send out the wrong information.

Before you replace or clean the sensor, fix the oil leak. Otherwise, the problem will only occur again.