This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.
Camshaft Position Sensor Circuit High Input
The P0343 code is a generic DTC that indicates the reading of the camshaft position sensor is out of range, specifically, too high a reading. When this happens, the PCM can’t properly estimate the position of the camshaft (it can guess it through other signals, but it doesn’t like doing that), which can greatly affect the timing for ignition and fuel injection.
If you’re curious about what this sensor is itself, its not more than a fixed electromagnetic sensor that’s connected to a rotating part on the camshaft that reads the position of a tooth in the camshaft, which in turn tells the PCM where the pistons’ are at in their range of motion. The position of the camshaft creates various gaps between the sensor which change the magnetic field to change the voltage from the sensor.
A P0342 code is typically caused by one, or a combination of, the following causes:
- A poorly performing battery, either dead or low in charge.
- An issue in the wiring harness / electric circuit between sensor and PCM. This could increase the impedance of the circuit as a whole, throwing the signal off.
- A defective starter motor
- Any issues in the starting circuit
- A faulty sensor. If the coil is open or shortened, the signal will be bonkers.
- Poor installation of the sensor is also a possibility, there’s a specific clearance for this. Install it according to manual.
Note we mentioned the most obvious one as the last possible cause. Too many mechanics will be eager and quick to replace very expensive components to beef up their billables, but this may in turn not end up fixing the issue. Obviously, if you’re working in your own car, you want to start by removing any other possibilities from the equation before settling for replacing the sensor.
The most obvious symptoms your car will show when you have a P0343, are:
- Check Engine Light on (duh)
- Poor acceleration
- Stalling (VERY common, particularly at low RPMs)
Note that there are many other issues that will present this kind of symptoms, and most of them will give you a P (powertrain) code of some sort.
To properly diagnose a p0343 and find the culprit, we recommend the typical approach to most sensor-related dtc codes. As follows:
- Check the battery condition
- Clear codes, take for a road test, see if issues persist, come back, check if the codes are back
- Take the sensor off, inspect visual condition.
- Inspect the harness and wiring for cuts, corrosion, dirt, etc.
- Inspect the position of the wiring and ensure it doesn’t go any near spark plug wires.
- Check for the internal resistence of the sensor and compare with manufacturer metrics (autodata or car manual, or a good brand-speficic obd2 scanner should have these)
- If that last value is off, or you can’t be bother to do step 6, just replace the part.
Typical mistakes when diagnosing a p0343 are not checking battery condition first, and ignoring the wiring.
A not so common mistake, but also one you don’t want to make, is using aftermarket sensors. Use only OEM parts for this kinda things.
How serious is this?
A p0343 is rather serious, as it can severely affect the engine performance, with stalling (which I don’t have to tell you it’s a dangerous thing if it happens in the middle of an intersection or incorporating to a highway) and very inconsistent power curves, as well as lower than normal MPGs
What repairs can fix the code?
Typical fixes that will sort out a p0343 are:
- Changing the battery if it’s in poor condition
- Replacing wiring / harness / connector if it’s damaged
- Replacing the sensor.
This code is sister to the P0342 and P0341, which are related to “low signal” and “range” (whilst this is high signal). If your car presents all three, it means the sensor’s reading is fully out of whack, which would point more to an electrical issue (broken sensors tend to “break” at one position, but don’t discard too quickly)
If you have a p0343 firing in your scanner, it’s better to take action on it immediately. The kind of problems you could have otherwise aren’t worth having.