P0340: Camshaft Position Sensor A Circuit (Bank 1 or Single Sensor)

What it means

The camshaft position (CMP) sensor signal is missing or implausible. The ECU uses CMP together with CKP to identify cylinder phase for sequential injection and coil-on-plug ignition; without CMP the engine may run on group injection or fail to start.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

Camshaft position sensor A on bank 1, or the single camshaft sensor on an engine with one bank, identifies camshaft phase for sequential fuel injection and ignition timing. P0340 sets when the ECU sees a missing or implausible signal from that sensor circuit, which can cause fallback operation, poor running, or a no-start.

Common causes

Most likely first.

1. Sensor failed
2. Timing chain stretched, throwing off sensor timing
3. Wiring fault

Symptoms

• Check engine light on
• Power loss especially in mid-rpm range
• Possible rough idle or stalling
• Increased fuel consumption

How to diagnose it

1. Record freeze-frame data and compare live camshaft and crankshaft synchronization while starting and running to see whether sensor A's phase signal is absent or inconsistent.
2. Inspect the bank 1 camshaft sensor A connector and harness for loose pins, oil or water intrusion, chafing, and heat damage.
3. Check the sensor circuit for opens, shorts, and poor power or ground connections according to the wiring information and manufacturer's specification.
4. If the circuit checks out, test sensor A's output and inspect its target or reluctor for damage or contamination.
5. If the signal is present but cam/crank correlation remains incorrect, check mechanical timing, including possible timing-chain stretch.

Common fixes

• Clean and secure the bank 1 camshaft sensor A connector.
• Repair damaged sensor wiring or its power and ground connections.
• Replace camshaft sensor A if it fails the specified signal test.
• Repair mechanical timing faults such as a stretched chain when confirmed by correlation checks.

Can I keep driving?

If the engine runs smoothly, a short, gentle trip for diagnosis may be possible, but avoid hard acceleration and high engine speeds. Rough running, stalling, or loss of power can make driving unsafe, and a worsening timing fault may lead to a no-start.