OBD codes / P0343
P0343
SeriousCamshaft Position Sensor A Circuit High
Treat P0343 with some urgency. The engine may run acceptably on the crank signal alone, but a failing cam sensor commonly causes hard starts and can progress to stalling or an intermittent no-start. Fine to drive carefully to a shop; unwise to depend on until repaired.
What this code means
The camshaft position sensor lets the computer know where the valvetrain is in its cycle so fuel injection and (on many engines) cylinder identification stay in sync with the crank. P0343 means the cam sensor's signal is reading HIGH — pegged at or above its expected maximum — the mirror image of P0342 (circuit low). The usual causes are a failed sensor, an open circuit or short to voltage in the wiring, or a corroded connector; a break in the circuit can leave the computer seeing a constant high level instead of the alternating pattern a spinning cam should produce. Symptoms match any lost cam signal: extended cranking, rough running, stalling, and on some engines a no-start — often intermittent and heat-related — so it belongs in the fix-promptly category.
Symptoms you might notice
- Hard starting or extended cranking
- Stalling or rough running
- Hesitation and reduced power
- Occasional no-start on some engines
- Check-engine light
What it costs to fix
Typical range: $80–$300 · about ~0.2–1 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Camshaft position sensor | $30–$120 | ~0.2–1 hrs |
| Wiring / connector repair | $10–$120 | ~0.5–1.5 hrs |
Typically a quick, inexpensive job — cam sensors are cheap and usually accessible on the head or timing cover. Intermittent wiring faults are the wildcard that adds diagnostic time.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0343 for my exact vehicle →
Frequently asked
What's the difference between P0343 and P0342?
Direction of the fault. P0342 means the cam sensor's signal is stuck low (dead sensor or short to ground); P0343 means it's stuck high (open circuit, short to voltage, or failed sensor). The diagnosis path — connector, wiring, then sensor — is the same.
Why won't my car start sometimes, then starts fine?
Intermittent cam-sensor faults are classic for this — a marginal sensor or connection drops out with heat or vibration, causing a random no-start or long crank, then works again. If P0343 is stored alongside that behavior, the cam sensor circuit is the prime suspect.
Can I drive with P0343?
Short, careful trips are usually okay since many engines fall back on the crank sensor, but stalling and no-starts are the real risk. Get it diagnosed promptly rather than waiting for it to strand you.
How much does it cost to fix P0343?
Usually inexpensive — the sensor is a cheap part and typically takes well under an hour to replace. If the fault is in the wiring instead, cost depends on how long the break takes to find.
Seeing P0343 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0343 for my vehicleRelated trouble codes
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Generic OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.