P3400: How to Diagnose & Fix — Cylinder Deactivation System Bank 1
2 vehicles · 2 makes · $1,800-$4,500 repair
How to diagnose and fix P3400: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Mazda CX-50 · 2025–2025
On the non-turbo 2.5L Skyactiv-G engine, the cylinder deactivation solenoid can fail at very low mileage, throwing a P3400 check engine light. In a documented 2025 CX-50 case the dealer found metal shavings in the oil filter and oil control valves and, after the code recurred, Mazda advised replacing the cylinder head on a nearly-new vehicle. Note this is currently a low-volume report rather than a confirmed widespread defect.
Common Symptoms
- Check engine light shortly after purchase (as early as 600 miles)
- P3400 fault code
- Metal shavings found in oil filter
How to Fix
Have the dealer scan for P3400, replace the failed cylinder deactivation solenoid(s), and inspect the oil filter and engine oil for metal contamination. If significant debris is present, request cylinder-head or short-block evaluation under powertrain warranty, and document all failures with the dealer to preserve coverage.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Mazda PYFA-12-360A solenoidOEMMazda PYFA-12-360A
Replace the specifically diagnosed cylinder-deactivation solenoid only after dealer/VIN confirmation Fitment/availability: Indexed direct OEM product page identifies PYFA-12-360A, sale price and Add to Cart, but explicitly exposes no app…
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Sources for this issue (1)
Chevrolet Camaro · 2010–2015
Automatic-transmission SS models with the 6.2L L99 V8 use Active Fuel Management lifters that are widely reported to collapse or stick, often leading to a misfire, valvetrain noise, and in many cases camshaft lobe damage. This problem is heavily documented across GM AFM-equipped V8 platforms and appears in Camaro owner complaints and forum repair threads. Repairs can become expensive because the cylinder heads and valvetrain must be opened, and many owners replace the cam and full lifter set once failure begins.
Common Symptoms
- check engine light with cylinder misfire
- ticking or tapping from valvetrain
- rough idle
- loss of power
- AFM/V4 mode drivability issues
- metal debris if cam lobe wears
How to Fix
Diagnosis usually starts with a persistent misfire, ticking, and cylinder-specific contribution loss; compression/leakdown and valvetrain inspection help confirm a failed lifter. Proper repair typically involves replacing the failed AFM lifters, trays/guides, and often the camshaft if lobe wear is present; many owners also replace related gaskets, head bolts, and oil pump components while inside. Continued driving can worsen metal contamination and increase repair cost.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Engine Valve LifterCross-ref213-1738
Fitment confirmed against the ShowMeTheParts catalog for this vehicle's year and engine.
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Sources for this issue (1)
Find P3400 by make
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P3400 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 P3400 mean?
P3400 stands for "Cylinder Deactivation System Bank 1." This code indicates the engine control module detected a fault in the cylinder deactivation (variable displacement) system on bank 1, the side of the engine containing cylinder number one. Cylinder deactivation closes the valves and cuts fuel to certain cylinders under light load to save fuel, using oil-pressure-operated control solenoids. When the system can't operate correctly, the module sets this code; you may notice reduced fuel economy, a slight performance change, or a warning light. The most common trigger is low oil level or poor oil pressure.
What are the most common causes of P3400?
The most common causes of P3400 are: Low engine oil level or low oil pressure, Clogged or dirty oil passages/lifters, Faulty active fuel management / cylinder deactivation solenoid, Failed deactivating lifter or collapsed lifter, Wiring or connector fault in the solenoid circuit, Sludge from missed oil changes, Faulty oil pressure sensor. The specific cause varies by vehicle.
How much does it cost to fix P3400?
Repair costs for P3400 range from $1,800 to $4,500, depending on the vehicle and root cause.
Which vehicles are affected by P3400?
Au7o has documented P3400 across 2 vehicle models from 2 manufacturers: Chevrolet, Mazda.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.