P0343: Camshaft Position Sensor "A" Circuit High Input (Bank 1 or Single Sensor)

P0343 means the camshaft position sensor signal voltage is higher than the ECU expects. This usually happens when the signal wire is open (broken), the sensor coil has failed open, the connector has lost contact, or the signal wire has shorted to a 12 V power source. P0343 is the inverse of P0342 and points to wiring or sensor faults rather than mechanical timing problems.

P0343 is a ignition-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0343 and illuminates the check engine light.

If your vehicle has triggered P0343, you may notice one or more of these symptoms:

• Hard or extended cranking
• Stalling shortly after start, especially when warm
• Limp mode with reduced throttle response
• Rough or surging idle
• Check engine light on

Here are the most common causes of P0343, ranked by how likely they are to be the culprit:

No - address this immediately. The ECU sees voltage on the cam sensor signal that is above the expected range, typically because the circuit is open or shorted to power. Sequential injection and VVT are degraded, so hard starting and stalling are likely. Diagnose before extended driving.

Follow these steps to pinpoint the root cause of P0343:

1. Read freeze-frame data and confirm whether P0343 sets at cranking, at idle, or only after warm-up. Heat-soak-only failures often indicate a degrading sensor
2. Inspect the sensor connector for full seating and signs of oil or coolant intrusion
3. Unplug the sensor and check resistance across its terminals if magnetic, or verify 5 V reference and ground if Hall-effect. An infinite resistance reading confirms an open coil
4. Check continuity of the signal wire from the sensor connector to the ECU pin. An open in the wire produces P0343 even with a healthy sensor
5. With ignition on and sensor unplugged, measure voltage on each pin. A constant 12 V reading on the signal pin indicates a wire shorted to power

Repair costs for P0343 vary depending on the root cause and your vehicle. Here are typical estimates:

P0343 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:

These codes are often seen alongside P0343 or indicate related issues: