Code P0340 on the 2024 Hyundai Elantra indicates a malfunction in the camshaft position sensor circuit for Bank 1 Sensor A (typically the intake camshaft). This sensor provides critical timing information the ECM uses for fuel injection and ignition timing.
Camshaft Position Sensor Role
The camshaft position sensor monitors the rotation and position of the camshaft, allowing the ECM to determine which cylinder is on its compression stroke for sequential fuel injection. It works with the crankshaft position sensor to establish precise engine timing.
P0340 Effects
Without reliable camshaft position data, the engine may experience hard starting, rough running, or no-start conditions. The ECM may default to a less efficient timing strategy or prevent starting entirely. Fuel injection timing becomes imprecise, affecting performance and emissions.
Common Causes
Sensor failure from heat exposure or internal electronics problems is most common. Damaged wiring from engine heat, oil contamination of the sensor connector, or timing chain/belt issues affecting the relationship between crankshaft and camshaft position can trigger P0340.
Diagnostic Approach
Verify the sensor produces a signal during cranking. Check wiring and connector condition. Test sensor output against specification. Compare camshaft position to crankshaft position to verify timing hasn't jumped due to chain/belt issues.