What P0340 means
The camshaft position sensor tells the computer which stroke each cylinder is on, so injection and spark land in the right cylinder at the right moment. P0340 means that signal is faulty — many engines keep running on crank data alone, but roughly, thirstily, and hard-starting.
What you’ll notice
- Long cranking before starting
- Rough running or misfire-like behaviour
- Stalling in some cases
- Check engine light
Likely causes and repair cost
Broad US independent-shop bands, parts and labour.
Can you drive with P0340?
Short-term yes, with degraded manners — but see the misdiagnosis note: on some engines this code is the first symptom of timing-chain stretch, which has a real deadline.
The misdiagnosis to avoid
Replacing sensors twice while a stretching timing chain drifts further out of sync. If a new sensor's code returns — especially with cold-start rattle or a companion P0016 — stop buying sensors: the correlation between cam and crank is physically wrong, and that's a chain conversation.
How P0340 actually gets set
The engine computer continuously compares what its sensors report against what its model of the engine expects. When a reading stays outside the expected window long enough to rule out noise, it stores a code and, if the fault affects emissions, illuminates the check engine light.
What a scan tool shows that the code does not
Freeze-frame data — the snapshot of engine speed, load, coolant temperature and fuel trim captured at the moment the code set. Those conditions frequently identify the cause faster than the code description does, because they tell you what the engine was actually doing when it failed.
The trap with this family of codes
Treating the code as a part number. A diagnostic trouble code names a circuit or a condition the computer observed, not the component that needs replacing. The gap between those two things is where most unnecessary parts spending happens.
What happens when you clear it
Clearing a code also resets the emissions readiness monitors, which inspection stations check. Arriving at a test with incomplete monitors fails just as surely as arriving with the light on, so fix the cause and let the system verify itself over several days of normal driving.
A steady light with no change in how the car drives means read the code within days. A flashing light, or any new symptom alongside the code, raises it immediately.
Describe what it’s doing in your own words and the symptom checker gives you a safe-to-drive verdict, ranked causes with costs, and notes to take to the shop — free, no sign-up.
A basic code reader costs around $25 and usually pays for itself the first time a warning light comes on. We compare them in choosing an OBD2 scanner.
Questions people ask
Why does my engine take longer to start now?
Without cam data the computer can't tell which of two possible strokes each cylinder is on, so many engines crank until they can guess-and-sync from crank data alone. Extended cranking that arrived with this code is the sensor's most common tell — and typically vanishes the day it's replaced.
Oil in the sensor connector — is that the fault?
It's a real finding: cam sensors live in pressurised oily housings, seals age, and oil wicks up the harness causing exactly these codes. The fix is the sensor plus honest cleaning of the connector — and on some engines a known repair for the wicking itself. Oil in the plug is evidence, not trivia; mention it.