P0343 Code: Camshaft Position Sensor A Circuit High (Bank 1)

What the P0343 code means

Sensor A is usually the intake camshaft sensor. Without it the computer does not know which stroke each cylinder is on, and variable valve timing stops working.

Position sensors come in two types. An inductive sensor has 2 wires and makes its own alternating voltage as the teeth pass by. A Hall effect sensor has 3 wires: a power supply, a ground and a square wave signal that switches between 0 and 5 V. The computer watches for the presence of the signal, for its shape and for how it lines up with the other position signals.

The P0343 code is set when the signal rises above its maximum. A high signal normally points to an open signal circuit or to a sensor ground that has been interrupted.

Remember that the code tells you where the computer saw the problem, not necessarily which part is bad. The wiring and the connector fail as often as the sensor itself.

P0343 code symptoms

• Long cranking time, or the engine does not start at all.
• Hesitation or cutting out while driving.
• Engine stalls, especially when it is hot.
• Loss of power, because variable valve timing is switched off.
• Check engine light on, sometimes together with misfire codes.

Likely causes of the P0343 code

1. Connector with oil, corrosion or a loose fit. The most frequent cause on camshaft sensors.
2. Damaged wiring from heat or rubbing, especially near the exhaust.
3. Failed sensor. An internal fault that often shows up once the sensor heats up.
4. Damaged tone wheel or reluctor ring, with broken or dirty teeth.
5. Timing that is out of phase or a stretched chain. This matters most on range codes.
6. Missing power reference, either 5 V or 12 V depending on the design.

How to diagnose the P0343 code step by step

1. Watch rpm and the sync status on the scan tool while someone cranks the engine.
2. Inspect the connector. Look for oil inside, green pins or a broken locking tab.
3. Check power and ground on 3-wire sensors: 5 V or 12 V on the supply pin and less than 0.1 V of drop on the ground side. A ground with too much drop is a classic cause of a high reading.
4. Measure the signal with an oscilloscope, or with a multimeter in frequency mode while cranking. On inductive sensors, measure AC voltage.
5. Look at the sensor tip. Metal shavings stuck to it or damage from an impact both matter.
6. On range codes, check the timing alignment and the stretch of the timing chain.

How to fix the P0343 code

• Clean or repair the connector and the wiring, including the sensor ground.
• Replace the sensor with an original-quality part.
• Repair the tone wheel or the timing if it is damaged.
• Run the crankshaft variation learn procedure if the manufacturer requires it.
• Clear the codes and verify the repair.

Technical reference data

• Inductive sensor: 2 wires, resistance of 200 to 1,200 ohms.
• Hall effect sensor: 3 wires, square wave signal from 0 to 5 V.
• Typical air gap: 0.5 to 1.5 mm (about 0.020 to 0.060 in).
• These are approximate values. Check the manufacturer data for your engine.

Brand-specific notes

Heat is a common reason these sensors misbehave. The engine dies when hot and starts again once it cools down.

P0343 on Chrysler

On many Chrysler engines the camshaft and crankshaft sensors fail with temperature. The engine stalls when hot and restarts after it cools.

P0343 on Nissan

On many Nissan engines the camshaft and crankshaft sensors fail with temperature. The engine stalls when hot and restarts after it cools.

P0343 on Hyundai

On many Hyundai engines the camshaft and crankshaft sensors fail with temperature. The engine stalls when hot and restarts after it cools.

P0343 on GM

After replacing the CKP sensor on a GM vehicle, you often have to run the variation learn procedure with a scan tool.

P0343 on Ford

After replacing the CKP sensor on a Ford, you often have to run the variation learn procedure with a scan tool.

Frequently asked questions about P0343