camshaft position sensor

P0343 Code: Camshaft Position Sensor A – Circuit High Input

In OBD2 Trouble Codes by Magnus Sellén7 Comments

What does the P0343 code mean?

p0343

The P0343 is triggered when the engine control unit receives a faulty signal or a high circuit input from the camshaft position sensor. Common causes are a bad camshaft position sensor or bad wiring. The camshaft position sensor is mounted on one of your camshafts. The P0343 is a general error code that applies to all makes and models from about the year 2000 onwards.

Some engines have several camshaft position sensors. Since the camshaft must be synchronized with the crankshaft position sensor at the starting torque, a common symptom is that your engine is difficult or impossible to start.

The 4-stroke crankshaft rotates two revolutions in one cycle and the camshafts rotate one revolution per cycle. Older cars usually have no camshaft sensor and only one crankshaft sensor. This is because older cars do not need to know which of the revolutions the crankshaft rotates at.

Each cylinder ignites the ignition and fuel once every two crankshaft revolutions, and it uses the camshaft sensor to detect whether the cylinder is in the intake or combustion cycle. Older cars without a camshaft sensor ignite the spark plugs twice per revolution, which is why it is called a “wasted spark”. So instead of igniting the ignition coils twice per revolution, when this is only required once per revolution, a camshaft sensor is used.

CodeDescriptionCommon CausesPossible Solutions
P0343Camshaft Position Sensor A - Circuit High InputFaulty Camshaft position sensor

Faulty 5v power supply wire from ECM

Corrosion/Bad connection in the CPS connector

Faulty ground wire to ECM

Short between power and ground wire

Low battery voltage / Faulty alternator

Faulty starter

Faulty Engine control unit (ECM)
Charge your car battery/Replace battery or fix the alternator charging problems

Repair any faulty wires between the camshaft position sensor and the engine control unit

Clean the camshaft position sensor from oil.

Clean the Camshaft position sensor connector

Replace Camshaft position sensor

Replace Engine control unit(ECM/PCM) (Rare)
SEE NEXT:  P0740 Code: Torque Converter Clutch Circuit Malfunction

P0343 Symptoms

The most common symptom of the P0343 code is the check engine light coming on, and the engine may have long starting times or it may not start at all. Sometimes, no symptoms at all can be expected for fault code P0343.

  • Check engine light/service engine soon light ON
  • The engine may not start
  • Engine dies when driving
  • Hard starting conditions/long cranking time
  • Rough idle
  • Rough acceleration
  • Hard shifting
  • No symptoms

Possible Causes

The most common cause of code P0343 is a faulty camshaft position sensor or faulty wires to the camshaft position sensor. A common misdiagnosis of this error code is that it could be a faulty timing belt drive causing the P0343 code. This error code indicates that there is a faulty circuit to the camshaft position sensor and should not be confused with the other error codes of the camshaft position sensor.

  • Faulty camshaft position sensor (most common)
  • Faulty 5v power supply wire from ECM
  • Corrosion/bad connection in the CPS connector
  • Faulty ground wire to ECM
  • Short between power and ground wire
  • Low battery voltage / faulty alternator
  • Faulty starter
  • Faulty engine control unit (ECM)

Possible Solutions

  • Charge your car battery, replace the battery, or fix the alternator charging problems
  • Repair any faulty wires between the camshaft position sensor and the engine control unit
  • Clean the camshaft position sensor from oil.
  • Clean the camshaft position sensor connector with a spray contact cleanerir?t=askamastermec 20&l=am2&o=1&a=B00006LVEU.
  • Replace camshaft position sensor
  • Replace engine control unit (ECM/PCM) (rare)

How to diagnose the P0343 code

This is a guide to how an automotive technician would diagnose this problem. It may require some knowledge of car electronics and the necessary tools, but you may get good information on how to do it right and how to do it without replacing non-defective parts. Always connect a car battery charger when doing any work on your car, because low voltage can trigger other error codes and even damage control units.

  1. Measure the voltage at idle (>14 volts) and with the engine off (>12 volts).
  2. Connect an OBD2 code scanner to verify the P0343 code.
  3. Inspect the camshaft position sensor for any external damages and make sure it is not fouled by oil from an oil leak. Inspect the connector and check for any corrosion or bad connections.
  4. Measure the ohms between the pins toward the camshaft sensor with a digital multimeterir?t=askamastermec 20&l=am2&o=1&a=B018EXZO8M. If you get no connection between the pins, there might be an open circuit inside the camshaft position sensor
  5. Remove the connector from the engine control unit and find the pins to the camshaft position. Do the same procedure with the camshaft position sensor connector plugged in. If you get no connection between these pins there might be an open circuit in the wirings. Check for any connection between the wires. If there is a connection between the wires, the wires are shorted.
  6. Check the signal from the crankshaft sensor with an oscilloscopeir?t=askamastermec 20&l=am2&o=1&a=B012938E76 (advanced).
  7. Replace camshaft sensor if faulty, and repair any wirings.
  8. Erase the code and take a test drive to verify that the problem is gone. Check your trouble code memory after some test drives to be sure that the problem is gone. The code may still be stored without the check engine light being on.
SEE NEXT:  P0405 Code: Exhaust Gas Recirculation (EGR) Sensor Circuit A Low

If you do not find any damage to the wires or the camshaft position sensor, it could be a defective engine control unit. But these cases are really rare, and you should do proper troubleshooting before replacing your engine control unit, as they are quite expensive.

Recommended Tools to Fix P0343

If you have further questions about the P0343 code, please comment below and I will answer you as soon as possible. If you have further questions about the car, you are welcome to ask them on our homepage.

To find all OBD2 codes. Check our OBD2 Code List.

Hello I'm Magnus, the owner and the writer of this website. I have been working with cars since I was 16 and I'm specialized with in-depth Automotive diagnostics. Also been driving drifting for the last 6 years. I'm here to give you answers to all your automotive questions and I hope that you enjoy our content.

7 thoughts on “ P0343 Code: Camshaft Position Sensor A – Circuit High Input ”

Comments
  1. I came across a 2010 VW Jetta 2.5 with a P0343 and all I get out of the 3 wire harness plug (using a power probe) is, 1) ground, 2) 4.8 volts and 3) nothing. This is unplugged by the way. Plugged up, it shows basically the same except there’s activity at the terminal (3) that had nothing at first, which would lead me to believe there’s some kind of activity going on there.

    Charging system tests okay, I cleaned the throttle body assembly, I got 60 psi fuel pressure while running, This code is now “permanent” by the way. This vehicle will not rev over 3k also. I tried an aftermarket cam sensor, used VW brand cam sensors (2) to no avail. Can an “off” timing belt cause all of this? This is a neighbor’s car and I was just trying to help out. I’m no better than somebody that knows nothing when it comes to European cars.

    1. Author

      @D.Hill

      The P0343 code is a bit tricky yes, the high input can in rare cases, be caused by a faulty timing.
      But for most of the times, it’s a faulty circuit either caused by a faulty camshaft sensor, a wiring issue or the engine control unit. You can also get problems if another sensor is faulty and making a short in the circuit.
      Sometimes the crankshaft sensor can cause problems with the camshaft sensor also

      But in this case, if you have checked the wirings and replaced the sensor to an OEM sensor, and checked the crankshaft sensor I would take a look at the timing.

  2. Thanks for your advice. Here is my issue.

    2002 BMW 540i (M62TU engine). I am not a mechanic but an enthusiast and do all the work on my cars.

    Started with a p0011 code, opened up the engine and replaced the timing guides, timing chains, rebuilt VANOS gears. Put it all together and ran great for a week, then bad. Took it apart again and found the bank 1 oil guide seal (intake cam) snapped and were causing oil pressure issues in the VANOS. Replaced bank 1 intake cam (checked by pro machine shop and was good cam), replaced VANOS gear with another rebuilt one, replaced timing trigger wheel. Car runs good, but now it has a constant P0343. Opened it up a third time and rechecked timing and it was perfect. Still getting P0343.

    Replaced sensors, swapped sides, etc with OE BMW sensors, no change
    Replaced battery, no change
    Replaced VANOS solenoids, no change
    Pin 1 has continuity, both sides
    Pin 2 has 12v, both sides, I know you say it should be 5V but both mine say 12 v. , is BMW different?
    Pin 3 has 12v, both sides
    Checked pins at DME and visually look good.
    Measure frequencies at pin 2 and 3 with the car running and both sides were at approximately 800 Hz with the car at 500 rpm, with the numbers varying from 600-1000Hz, both sides.

    Delete code and on the first start there is no code, no matter how long I drive it. At the second start the code appears.

    Any other ideas? Thank You!

    1. Author

      First, you should replace both bolts to the camshaft sensors to make sure they are not magnetic. Make sure the harness is ok. On the M62TU engine, there is a common problem with the thermostat housing heater is going bad and pushing coolant inside of the wires into the engine control unit. Check the engine control unit connector and make sure that there is no corrosion or coolant inside the connector and the control unit.
      Then you have to measure the signals from the camshaft sensors both directly on them, and at the engine control unit connector, to see if you can see any differences in the signal.

  3. HI
    I have opel corsa 2005 3 piston engine (Engine starts good but no Ecceleration at all)
    max rpm 2000
    plzzz need help

  4. Having trouble locating the Crankshaft Position Sensor on a 1993 Oldsmobile Cutlass Supreme with a 3.4 liter engine? I am experiencing issues of no power to the fuel injection harness as well as no spark coming from the spark plug?

  5. Due to a very high demand and high ammount of comments, you have to wait for some time for your car questions to get answered. If you want to get fast answers from a certified master technician you can ask your questions here:
    Ask A Mechanic

Leave a Comment