P0343 code: Mechanic advice to diagnose & fix

P0343 Code
Camshaft Position Sensor Circuit High Input

Our mechanic shows you how to diagnose a P0343 code (“Camshaft Position Sensor Circuit High Input”), and the electrical issues that could be causing it. Your car’s symptoms could include engine bucking, surging, stalling, taking longer than usual to start, or not starting at all.

Watch this video:

Check Engine Light? Camshaft Position Sensor Circuit High Input – Code P0343

You can watch more of our how-to and diagnostic videos in our video library.

What is code P0343 and what does it mean?

Error code P0343, also known as “Camshaft Position Sensor Circuit High Input,” means a car’s Powertrain or Engine Control Module (PCM or ECM) detects a voltage problem from the cam sensor.

The camshaft position sensor monitors the camshaft’s position and movement, which it sends to the PCM to ensure the correct fuel injection timing and amount of fuel and air that’s let in and out. Make sure you watch our featured P0343 video for more details on how a cam sensor works.

How serious is a P0343 code?: Is it OK to drive with P0343? 

If your engine still runs with this P0343 check engine light, it’s best to repair it as soon as possible. There is a fair chance that the engine will decide to stop running entirely when the sensor completely fails, and that could leave you stranded. In between the time when the check engine light turns on and the engine stops running, your starter and battery may end up receiving additional wear from the extended engine cranking. With it being a DIY-friendly repair, it’s best to just nip this one early!

What are common P0343 code symptoms?

P0343 trouble code symptoms can include: 

  • Your Check Engine light is on
  • Extended crank: When you crank your car, it takes longer for the engine to start than usual
  • Your engine bucks or surges
  • Stalling
  • Your engine won’t start
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What causes P0343?

The most common P0343 cause is a faulty camshaft position sensor.

Other typical P0343 causes include a faulty or damaged cam sensor connector or wiring, or PCM issues.

How do I diagnose and fix a code P0343?

Use an OBD-II scan tool or code reader that graphs engine data to test the cam sensor

With the engine running, use a scan tool or code reader to watch the data for cam sensor high to low and low to high (in our featured P0343 video, our mechanic selects both “CMP Sensor – High to Low” and “CMP Sensor – Low to High” on the scan tool he uses).

Test the cam sensor connector, wiring, and the PCM

To test the sensor connector and wiring, disconnect the connector and use a multimeter to measure the voltage. You can also use a test light; if it lights up, you’ll know the connector and wire have good ground or voltage, and the PCM is working correctly. Our mechanic walks you through how to test with a multimeter at 2:49, and test light at 3:56 in our featured P0343 video.

If you’ve confirmed the connector and wire have good voltage, and that the PCM is working right, that narrows down the issue to the cam sensor, which you’ll need to replace.

If you replace the cam sensor, make sure you clear the Check Engine light and drive your vehicle to resolve the P0343 code.

Need to replace your camshaft position sensor?

Find the camshaft position sensor you need for your year, make, and model now, so you can save time and money by replacing it yourself.

Shop our other partstools, and accessories, including OBD2 scan tools and code readers, now: 1aauto.com

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