Few situations are more alarming than having your 2021 Acura ILX stall while waiting at a traffic light. The engine dies without warning, dash lights illuminate, and you scramble to restart before traffic moves. P0340—Camshaft Position Sensor Circuit Malfunction—reveals the likely source.
What the Camshaft Position Sensor Does
The camshaft position sensor monitors the rotation of the camshaft, providing critical timing information to the engine computer. This data determines when to fire spark plugs and pulse fuel injectors. Without accurate camshaft position information, the engine can't maintain proper timing—or may not run at all.
How Sensor Problems Cause Stalling
When the camshaft sensor fails or sends erratic signals, the engine computer loses track of valve timing. At idle, where timing must be precise and there's minimal momentum, signal loss causes immediate stalling. The engine might restart after cooling, only to stall again as the sensor heats up.
Common Causes of P0340 on the ILX
Camshaft sensor circuit problems typically result from:
- Sensor failure - Internal electronics fail from heat or age
- Wiring damage - Corroded connectors, chafed wires, broken connections
- Timing belt/chain stretch - Affects cam/crank sensor correlation
- Tone ring damage - The reluctor wheel can become damaged
- ECU software issues - Rare, but possible
Why Stalling Occurs at Idle
At higher RPM, the crankshaft position sensor can partially compensate for camshaft sensor issues. At idle, where rotational speed is low and margins are tight, sensor irregularities immediately cause instability—explaining why the ILX drives fine but dies at stoplights.
Diagnostic Process
- Retrieve all stored codes and freeze frame data
- Monitor camshaft sensor signal with oscilloscope
- Check wiring continuity and connector condition
- Compare cam and crank sensor correlation
- Inspect for timing belt wear if mileage warrants
Repair Costs
- Camshaft position sensor: $150-$350
- Wiring repair: $100-$300
- Timing chain/belt inspection: $100-$200