Can P0340 cause the car to not start at all?

Yes. Some PCMs will not fire injectors without a valid cam signal. Others use crank sensor data as a fallback. Whether it starts depends on the specific vehicle and PCM logic.

How do I know if the timing chain is the real cause?

If you hear a rattle on cold starts, especially one that clears as oil pressure builds, that is a timing chain warning. A stretched chain will also set P0017 or similar cam-crank correlation codes.

Bank 1 Sensor A -- is there a Bank 2 version?

Yes, P0345 is the Bank 2 cam sensor circuit code. On V-engines with variable valve timing on both banks, each bank has its own sensor.

Codes › P0340

P0340: The camshaft position sensor on Bank 1 has a circuit fault

Camshaft Position Sensor A Circuit Malfunction (Bank 1 or Single Sensor)

High severityCan you keep driving?

Drive with caution. The engine may start and run with a failed cam sensor, but fuel and ignition timing will be imprecise. On variable valve timing engines, expect significant performance loss. If it will not start, have it towed.

What it means

The camshaft position sensor tells the PCM where the camshaft is positioned relative to the crankshaft. The PCM needs this to determine which cylinder is on its compression stroke so it can fire the correct injector and coil. P0340 means the PCM received no usable signal from the sensor circuit, as opposed to P0341 which is a range or performance fault. Without cam position data, the PCM falls back to crank sensor data alone, which means it may need extra cranking to synchronize and fueling will not be as precise. On engines with variable valve timing, this code can also disable the VVT system entirely.

Common causes

Failed camshaft position sensorThe Hall-effect sensor element fails. Common on engines with 100,000 or more miles.
Open or short in the cam sensor wiring harnessThe harness near the cam cover is exposed to oil and heat. Damaged insulation causes the circuit to fail.
Damaged camshaft reluctor ring or tone wheelDebris from timing chain wear can chip the reluctor ring, breaking the signal pattern.
Timing chain stretch or jumped timingA stretched chain shifts cam position relative to crank. The sensor signal is present but out of phase, which can also set this code.
Failed PCM input circuit for the cam sensorUncommon. Confirm the sensor and wiring are good before suspecting the PCM.

What it costs

Camshaft position sensor replacement$100 to $350 installed
Wiring or connector repair$80 to $250
Timing chain and guides replacement (if stretched)$800 to $2,500 depending on engine

Symptoms

Check engine light on, often steady
Hard starting or extended crank time
Rough idle and reduced performance
Variable valve timing disabled (on VVT engines)
Possible stalling under load

What to do next

Inspect the wiring and connector at the sensor first. A broken wire near a hot valve cover is a common and cheap fix. If wiring is fine, replace the sensor. If the code returns immediately, or if you also have symptoms like a rattle on start-up, have a shop check the timing chain. A skipped or stretched chain requires prompt repair because continued operation can damage valves and pistons.

Lewis shows the cam and crank sensor correlation data so you can see whether the two signals are synchronized or whether there is a timing chain phasing issue. Download Lewis.

Related codes

FAQ

Can P0340 cause the car to not start at all?: Yes. Some PCMs will not fire injectors without a valid cam signal. Others use crank sensor data as a fallback. Whether it starts depends on the specific vehicle and PCM logic.
How do I know if the timing chain is the real cause?: If you hear a rattle on cold starts, especially one that clears as oil pressure builds, that is a timing chain warning. A stretched chain will also set P0017 or similar cam-crank correlation codes.
Bank 1 Sensor A -- is there a Bank 2 version?: Yes, P0345 is the Bank 2 cam sensor circuit code. On V-engines with variable valve timing on both banks, each bank has its own sensor.