P0340 on Mazda
Camshaft Position Sensor Circuit Malfunction
P0340 on Mazda vehicles indicates camshaft position sensor circuit malfunction. Au7o has documented this code across 2 Mazda models — most commonly on 626, MX-5 Miata. This code means the engine computer lost or received an erratic signal from the camshaft position sensor. That sensor tells the computer the exact position and speed of the camshaft, which it uses together with the crankshaft sensor to time fuel injection and spark precisely. When the camshaft signal is missing, intermittent, or out of range, the computer sets P0340. Symptoms often include hard starting, stalling, rough running, or a no-start because the engine can't time itself correctly. Typical repair costs on Mazda range from $40 to $450, depending on the specific model and root cause.
Common Causes of P0340
- •Failed camshaft position sensor
- •Corroded or loose sensor connector
- •Damaged or shorted sensor wiring
- •Bad reluctor/tone ring on the camshaft
- •Loose timing chain/belt or jumped timing
- •Metal debris or oil contamination on the sensor tip
- •Poor sensor power or ground supply
- •Faulty PCM/ECM (rare)
P0340 on Mazda by Model
Mazda 626(1 issue)
- KL V6 distributor internal oil seal leak / cap-and-rotor fouling1993-1999
The 2.5L KL-DE V6 uses a cam-driven distributor with an internal O-ring/oil seal at the base and a shaft bushing. As the seal hardens with age, engine oil weeps up the shaft and pools inside the distributor cap, fouling the cap and rotor and shorting the ignition. On higher-mileage cars the shaft bushing also wears, allowing shaft wobble that both worsens the leak and disturbs the pickup signal. The result is a rough-running, misfiring, hard-starting or stalling V6 that many owners chase before finding the source. This is a well-known KL-engine quirk shared with the MX-6 and Ford Probe GT.
Mazda MX-5 Miata(1 issue)
- Cam/Crank Angle Sensor (CAS) O-ring oil leak on 1.8L engines1994-1999
On 1.8L BP engines, the Cam Angle Sensor (commonly called the CAS) mounts at the rear of the cylinder head, engaging the camshaft, and is sealed to the head by a single rubber O-ring. With age and heat cycling the O-ring hardens and shrinks, letting oil weep out of the back of the head. This is widely cited as the single most common oil-leak source on NA/NB Miatas; it typically fails before the valve-cover gasket. The oil runs down onto the nearby heater hoses (which it can rot) and the bellhousing. It is a nuisance leak rather than a failure, but a badly heat-soaked or oil-fouled CAS can also contribute to intermittent driveability faults.
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View P0340 across all makes →Frequently Asked Questions
What does P0340 mean on Mazda?▼
P0340 stands for "Camshaft Position Sensor Circuit Malfunction." This code means the engine computer lost or received an erratic signal from the camshaft position sensor. That sensor tells the computer the exact position and speed of the camshaft, which it uses together with the crankshaft sensor to time fuel injection and spark precisely. When the camshaft signal is missing, intermittent, or out of range, the computer sets P0340. Symptoms often include hard starting, stalling, rough running, or a no-start because the engine can't time itself correctly. On Mazda specifically, this code is documented across 2 models.
What causes P0340 on Mazda vehicles?▼
Common causes on Mazda: Failed camshaft position sensor, Corroded or loose sensor connector, Damaged or shorted sensor wiring, Bad reluctor/tone ring on the camshaft, Loose timing chain/belt or jumped timing. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0340 on a Mazda?▼
Repair costs on Mazda range from $40 to $450, depending on the specific model and root cause.
Which Mazda models have P0340 documented?▼
Au7o has documented P0340 on 2 Mazda models: 626, MX-5 Miata.