The Defender P400 uses the AJ300P — a 3.0-litre inline-six petrol engine from Jaguar Land Rover's Ingenium family, fitted to the L663-generation Defender from 2019 onwards. It's a mild-hybrid (MHEV) unit, meaning it pairs the combustion engine with a 48V electrical system that supports stop-start, coasting and a small power boost. The DC-DC converter that manages the 12V/48V interface is a known failure point, which is why we replace it as standard on every P400 rebuild. The P400 sits above the P300 in the Defender petrol range and shares its engine family with the P400e plug-in hybrid (discontinued after 2020). Land Rover Defender P400 Engine Codes AJ300P (L663) A 3.0-litre inline-six petrol MHEV fitted to the Defender P400 from 2019 to present (L663 generation). Known for DC-DC converter failure — see the callout above. We replace the DC-DC converter, timing chains, bearings and gaskets as standard on every rebuild. Check Your AJ300P Defender P400 → [link to quote form] Land Rover Defender P400 Engine Compatibility Because the Defender P400's AJ300P is a mild-hybrid unit with a 48V electrical system, compatibility isn't just about the engine block — the DC-DC converter, wiring and ancillaries all need to match your exact build specification. Before we quote or supply anything, we confirm: Your exact engine code (AJ300P) via registration or VIN Your generation (L663) Drivetrain and ancillary specification, including the MHEV system Any electronics or ECU considerations specific to your exact build This is why we always start with your registration rather than a generic P400 quote — it protects you from paying for parts that don't fit your actual vehicle. Land Rover Defender P400 Applications by Generation Generation Chassis Years Engine Code Fuel L663 L663 2019–present AJ300P Petrol MHEV Land Rover Defender P400 Engines by Year Year Generation Engine Code Fuel Service 2019 L663 AJ300P Petrol MHEV Rebuild / Replacement 2020 L663 AJ300P Petrol MHEV Rebuild / Replacement 2021 L663 AJ300P Petrol MHEV Rebuild / Replacement 2022 L663 AJ300P Petrol MHEV Rebuild / Replacement 2023 L663 AJ300P Petrol MHEV Rebuild / Replacement 2024 L663 AJ300P Petrol MHEV Rebuild / Replacement 2025 L663 AJ300P Petrol MHEV Rebuild / Replacement 2026 L663 AJ300P Petrol MHEV Rebuild / Replacement We Cover Every Land Rover Defender P400 Model Year: ✓ Land Rover Defender P400 2019 Engine Rebuild ✓ Land Rover Defender P400 2020 Engine Rebuild ✓ Land Rover Defender P400 2021 Engine Rebuild ✓ Land Rover Defender P400 2022 Engine Rebuild ✓ Land Rover Defender P400 2023 Engine Rebuild ✓ Land Rover Defender P400 2024 Engine Rebuild ✓ Land Rover Defender P400 2025 Engine Rebuild ✓ Land Rover Defender P400 2026 Engine Rebuild If your registration year isn't listed above, get in touch — we'll confirm availability directly against your reg. Land Rover Defender P400 Engine Sizes ✓ Land Rover Defender P400 3.0 Litre Engine (AJ300P, I6 MHEV) Land Rover Defender P400 Fuel Types ✓ Land Rover Defender P400 Petrol MHEV Engine Rebuilds Land Rover Defender P400 Engine Costs A Land Rover Defender P400 engine rebuild starts from £2,800. A full replacement engine and fitting service is also available. Exact pricing depends on the condition of your existing engine and the parts required — submit your registration for a fixed-price quote within 30 minutes. Related Land Rover Defender Variants Looking for a different Defender engine? We also cover: [Defender D200 Engine →] · [Defender D250 Engine →] · [Defender D300 Engine →] · [Defender D350 Engine →] · [Defender P300 Engine →] · [Defender P525 V8 Engine →] ← View All Land Rover Defender Engines Frequently Asked Questions What engine does the Land Rover Defender P400 use? The Defender P400 uses the AJ300P — a 3.0-litre inline-six petrol mild-hybrid (MHEV) engine from Jaguar Land Rover's Ingenium family, fitted to the L663 generation from 2019 onwards. How much does a Land Rover Defender P400 engine rebuild cost? Rebuilds start from £2,800. Exact price depends on condition and parts required — submit your reg for a fixed-price quote. Which engine code is fitted to my Defender P400? The Defender P400 uses the AJ300P engine code. Enter your registration on this page and we'll confirm your exact spec before you're quoted anything. Do you rebuild AJ300P Defender P400 engines? Yes. We replace timing chains, bearings, gaskets and the DC-DC converter as standard on every P400 rebuild. Do you supply used Defender P400 engines? Yes, in some cases a matched low-mileage used engine is the right option. Our team will advise honestly once we've matched your registration and understood your situation. Can you recover my Defender P400 if the engine has failed? Yes — nationwide recovery is available from £70, and most vehicles are collected within a few hours of booking. How long does a Defender P400 engine rebuild take? Most rebuilds are completed within 3-5 working days from the time your vehicle arrives at our workshop. Is rebuilding better than fitting a used engine? For most Defender owners, yes. A rebuild removes the compatibility risk that comes with an unknown used unit's history, and comes with a 12-month unlimited-mileage warranty — often longer and more comprehensive than what a used engine supplier offers. <a name="quote-form"></a> Get Your Free Land Rover Defender P400 Fixed-Price Quote [Quote Form: Registration Number | Postcode | Name | Phone | Email | Issue/Enquiry Type (dropdown: Engine Failure / Replacement Needed / General Enquiry) | Submit] Most quotes returned within 30 minutes during working hours. json { "@context": "https://schema.org", "@graph": [ { "@type": "Organization", "@id": "https://landrovergarage.co.uk#organization", "name": "Land Rover Garage", "url": "https://landrovergarage.co.uk", "email": "info@landrovergarage.co.uk", "telephone": "+44 01268 944 234", "sameAs": [ "https://facebook.com/landroverrebuildgarageuk", "https://twitter.com/landroverrebuildgarageuk", "https://instagram.com/landroverrebuildgarageuk", "https://tiktok.com/@landroverrebuildgarageuk" ] }, { "@type": "AutoRepair", "@id": "https://landrovergarage.co.uk#autorepair", "name": "Land Rover Garage – Defender P400 Engine Rebuild Specialists", "url": "https://landrovergarage.co.uk/defender-p400-engines", "telephone": "+44 01268 944 234", "email": "info@landrovergarage.co.uk", "priceRange": "£££", "address": { "@type": "PostalAddress", "streetAddress": "Unit A5 Windsor Road, Commercial Estate, Ramsden Heath", "addressLocality": "Billericay", "postalCode": "CM11 1QE", "addressCountry": "GB" }, "openingHours": "Mo-Fr 09:00-18:00, Sa 11:00-14:00", "areaServed": "GB", "parentOrganization": { "@id": "https://landrovergarage.co.uk#organization" }, "brand": { "@type": "Brand", "name": "Land Rover" } }, { "@type": "Service", "serviceType": "Land Rover Defender P400 Engine Rebuild & Replacement", "provider": { "@type": "AutoRepair", "name": "Land Rover Garage" }, "areaServed": "GB", "offers": { "@type": "Offer", "priceCurrency": "GBP", "price": "2800", "description": "Land Rover Defender P400 engine rebuild starting price, AJ300P" } }, { "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "What engine does the Land Rover Defender P400 use?", "acceptedAnswer": { "@type": "Answer", "text": "The Defender P400 uses the AJ300P — a 3.0-litre inline-six petrol mild-hybrid (MHEV) engine from Jaguar Land Rover's Ingenium family, fitted to the L663 generation from 2019 onwards." } }, { "@type": "Question", "name": "How much does a Land Rover Defender P400 engine rebuild cost?", "acceptedAnswer": { "@type": "Answer", "text": "Rebuilds start from £2,800. 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A rebuild removes the compatibility risk that comes with an unknown used unit's history, and comes with a 12-month unlimited-mileage warranty — often longer and more comprehensive than what a used engine supplier offers." } } ] } ] }

We continue to rebuild and replace AJ300P engines for every Defender P400 on the road.