You turn the key and the engine just won’t start smoothly. Or it starts but suddenly stalls and jerks while driving. You connect your scanner and see P0340. Don’t panic: this is usually a sensor or a loose plug, and it’s manageable. However, it’s wise to check it quickly because the car can leave you stranded.
Quick answer: Fault code P0340 means there is a problem in the camshaft position sensor circuit. This sensor tells the computer where the camshaft is, which is necessary for correct ignition and injection. The most common cause is a dirty sensor tip or a loose connector. If the signal drops out, the engine runs poorly or won’t start, so address it promptly.
What does fault code P0340 mean?
The camshaft position sensor reads the position of the camshaft and sends it to the engine computer. The computer needs this signal to ignite and inject fuel at the right time. If the computer sees no signal, an illogical signal, or a lost signal, it sets P0340. The engine then often falls back on the crankshaft signal, but that runs less smoothly.
Severity: orange to red. The car can stall or fail to start completely. This is not a code to ignore. If the car still runs, schedule a check quickly. If it won’t start or keeps stalling, treat it as red.
Symptoms
Hard or no start. The engine cranks for a long time or doesn’t start at all because the camshaft signal is missing.
Stalling or jerking while driving. If the signal drops out briefly, the engine stutters or stalls on the road.
Power loss and engine warning light. The car accelerates poorly and the engine warning light stays on.
Possible causes (from cheap to expensive)
Dirt or metal particles on the sensor tip (€0 to €20). Metal filings or oil on the tip disrupt the signal. Cleaning often costs nothing.
Loose connector or damaged wiring (€10 to €80). A poor connection or a broken wire interrupts the circuit.
Defective camshaft position sensor (€20 to €120). The sensor itself is worn out and no longer gives a reliable signal.
Underlying timing belt or camshaft problem (variable). Less common, but a shifted timing belt or camshaft also causes this code.
Step-by-step plan: how to find the cause yourself
- Read the start signal. Connect a scanner and check the live data to see if a camshaft or RPM signal is received during startup. If it stays at zero, you’re close to the cause.
- Check the connector and wiring. Disconnect the plug and look for corrosion, loose pins, or a broken wire. Poor contact is a common culprit.
- Inspect the sensor tip. Unscrew the sensor and check for dirt, oil, or metal particles on the tip. Clean it carefully and reinstall it.
- Test the sensor. Use a multimeter to measure the resistance or signal of the sensor and compare it with your car’s specifications.
- Replace the sensor and clear the code. If the sensor doesn’t give a good signal, replace it and clear P0340. If the code doesn’t return, the sensor was the cause.
What does it cost?
Yourself: clean the sensor tip. €0 to €20. The cheapest attempt, often enough for a dirty tip.
Yourself: install a new sensor. €20 to €120 for the part, usually doable with a few steps.
Garage: diagnosis and repair. €80 to €250, depending on whether it’s the sensor, wiring, or timing belt.
Fix it yourself or go to the garage?
You can often clean the sensor tip, check the connector, and replace the sensor yourself, especially if the sensor is easily accessible. If everything points to the wiring or a shifted timing belt, then a garage is wiser. The beauty of P0340 is that you start cheap and only scale up if necessary.
The right tool for this code
For P0340 you want to be able to do two things: read and clear the code, and see in live data whether the camshaft signal is coming in during startup. These three devices fit that. Start with the CarPal; if you want to measure deeper or test actuators, then use the OBDeleven or the Launch.
View the Topdon CarPal →
View the OBDeleven 3 →
View the Launch CRP919X →Related fault codes
P0340 belongs to a family of codes related to position sensors. If you encounter one of these, the approach is similar: P0341 (camshaft sensor signal out of normal range), P0335 (crankshaft position sensor problem), and P0016 (crankshaft and camshaft out of sync). If you don’t yet know how to read and clear codes, first read reading and clearing fault codes.
Frequently Asked Questions
Can I keep driving with P0340?
Sometimes it will, but unreliably. The car may stall or fail to start. If it still runs, schedule a check soon and avoid long trips until it’s fixed.
Why won’t my car start with P0340?
The computer misses the camshaft signal and therefore doesn’t know exactly where the camshaft is. Without that signal, it cannot ignite and inject properly, so the engine won’t start.
Can I replace the camshaft position sensor myself?
Often yes. If the sensor is easily accessible, it usually means unplugging the connector, removing a bolt, installing a new sensor, and clearing the code.
Is P0340 the same as a crankshaft sensor fault?
No. P0340 concerns the camshaft position sensor. The crankshaft position sensor has its own code (P0335). They do work together, so if in doubt, check both.
In short
• P0340 = a problem in the camshaft position sensor circuit.
• Start by cleaning the sensor tip and checking the connector; that is often enough.
• If that doesn't solve it: test the sensor and replace it.
• Take it seriously, as the car may stall or fail to start.