P0340 on Mazda: How to Diagnose & Fix
Camshaft Position Sensor Circuit Malfunction
4 Mazda models · 4 documented issues · 2 critical · $40-$1,800 repair
P0340 on Mazda by model: symptoms, diagnosis and fix
The KL-DE 2.5L V6 distributor is driven off the rear cylinder head and has internal and external O-ring seals that commonly fail with age. As the shaft bushings wear, oil migrates past the seals and pools inside the distributor cap, causing misfires, rough running, and ultimately no-spark crank-no-start conditions. RepairPal lists 'Crank but No Start Condition and No Spark' as the most commonly reported MX-6 problem, frequently traced to a failed distributor. Once the shaft itself develops play (wobble), the internal seal cannot be effectively replaced and the entire distributor must be replaced or rebuilt.
Common Symptoms
- Crank but no start, no spark
- Oil pooled inside distributor cap
- Oil drip below distributor onto transaxle
- Misfires, rough running, hesitation under load
- Intermittent stalling once warm
How to Fix
Inspect the distributor cap for oil contamination. If only the external O-ring is leaking and shaft has no play, replace the small base O-ring (~$3) and the cap/rotor. If the shaft is worn or oil has reached the internal pickup, replace the distributor assembly (reman units approximately $200-$300 plus core). Always replace cap, rotor, and plug wires at the same time.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Cardone New 84-35620 electronic distributorOEMCardone 84-35620
Complete distributor for confirmed internal/shaft failure on the 1993-1994 2.5L V6 branch Fitment/availability: The inspected direct page showed Cardone 84-35620 in stock at $240.94 with Add To Cart and lists a six-cylinder Hall-effect d…
- Cardone 31-35602 remanufactured distributorOEMCardone 31-35602
Complete distributor for confirmed internal/shaft failure on the 1995-1997 2.5L V6 branch Fitment/availability: The inspected direct retail page lists Cardone reman 31-35602 for 1995-1997 Mazda MX-6, application ID T0T57271/KF34-18-200-s…
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Sources for this issue (3)
The 3.0L Duratec V6 uses two timing chains, one per cylinder head, each with a hydraulic tensioner and plastic guide rails. The tensioners bleed down when the engine sits, so the classic first symptom is a rattle or slap from the front of the engine for the first one to thirty seconds after a cold start, fading as oil pressure builds and re-extends the tensioner. Worn guides, a tensioner that no longer holds pressure, or a stretched chain let that slack persist, and because the 3.0L Duratec is an interference design, a chain that jumps time can put valves into pistons. Neglected oil changes accelerate this: sludge starves the tensioners and wears the guides. This is engine-code specific - it does not apply to the 2.0L Zetec, 2.3L or 2.5L four-cylinder Tributes, which use different valvetrain drive designs and failure modes.
Common Symptoms
- Rattle or slap from the front of the engine for a few seconds after a cold start
- Rough idle
- Reduced power
- Check engine light with camshaft/crankshaft correlation codes
- Metallic debris found in the oil pan
How to Fix
First isolate accessory-drive tensioner noise from an internal timing rattle. For a confirmed 3.0L timing-drive fault, replace both chains, tensioners, guides and the front-cover sealing components as a complete repair; inspect oil pressure and sprockets while open.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Cloyes 9-0708S complete timing-chain kit$205
2001-2006 and 2008-2011 Mazda Tribute 3.0L V6 only. The direct listing includes two chains, tensioners, guides and crank sprocket; 2007 is not listed and front-cover gaskets/seals remain separate.
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Sources for this issue (3)
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.
Common Symptoms
- Oil pooled inside the distributor cap
- Rough idle and random misfire
- Hard starting, especially when damp
- Intermittent stalling
- Hesitation under acceleration
How to Fix
First-line fix is replacing the cheap base O-ring/seal (a few dollars) plus a fresh cap and rotor and cleaning the shaft, which cures most cases; applying a little sealer at the cap on reinstall helps. If the distributor shaft has visible play/wobble, the whole distributor must be replaced (reman ~$150-300 plus labor). Keeping oil out of the cap also prolongs plug-wire and coil life.
Sources for this issue (3)
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.
Common Symptoms
- Oil weep/drip at the rear of the cylinder head
- Oil-soaked heater hoses near the firewall
- Burning oil smell
- Occasional heat-soak stall or hard restart when hot (severe cases)
How to Fix
Remove the CAS, discard the old O-ring, and install a fresh O-ring (a Viton -222 size is commonly used) lightly lubricated with clean oil; reindex the CAS to its factory alignment on reinstall so ignition timing is preserved. The part is a few dollars; most owners do it themselves. A shop visit is inexpensive. If a heat-soaked sensor is causing driveability faults, replace the CAS unit itself.
Sources for this issue (3)
P0340 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0340 mean on a 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 it is documented across 4 models: MX-6, Tribute, 626, MX-5 Miata.
What are the most common causes of P0340?
The most common causes of P0340 are: 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). The specific cause varies by vehicle.
How much does it cost to fix P0340 on a Mazda?
Published repair estimates on Mazda range from $40 to $1,800 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0340 on a different make?
View P0340 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.