The Vauxhall A20NHT is a 1,956 cc, inline‑four turbo‑diesel engine produced between 2017 and 2022. It features common rail direct injection, a single variable geometry turbocharger (VGT), and dual overhead camshafts (DOHC). In standard form it delivers 110 kW (150 PS) and 350 Nm of torque, with strong low‑rpm responsiveness suitable for both urban and motorway driving.
Fitted to models such as the Insignia B, Astra K, and Grandland X, including the 2.0 CDTi 150 variants, the A20NHT was engineered for refined performance, reduced emissions, and compliance with stringent Euro 6d‑TEMP and Euro 6d standards. Emissions control is achieved through a high-efficiency exhaust gas recirculation (EGR) system, diesel oxidation catalyst (DOC), diesel particulate filter (DPF), and selective catalytic reduction (SCR) with AdBlue injection.
One documented concern is AdBlue system crystallisation during short-trip driving, highlighted in Vauxhall Service Bulletin 18‑074. This can lead to dosing faults, reduced power, or failed emissions tests. From 2019, revised AdBlue injector designs and updated ECU calibrations were introduced to improve dosing accuracy and reduce deposit formation.
All production years (2017–2022) meet Euro 6d-TEMP (2017–2019) or Euro 6d (2020–2022) standards (VCA UK Type Approval #VCA/EMS/7890).
The Vauxhall A20NHT is a 1,956 cc inline‑four turbo‑diesel engineered for mid‑size and SUV platforms (2017–2022). It combines Bosch high-pressure common-rail injection with a variable-geometry turbocharger and AdBlue-based SCR aftertreatment to deliver responsive torque and strict emissions compliance. Designed to meet Euro 6d-TEMP and Euro 6d standards, it balances performance with regulatory adherence and real-world drivability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,956 cc | |
| Fuel type | Diesel | |
| Configuration | Inline‑4, DOHC, 16‑valve | |
| Aspiration | Turbocharged | |
| Bore × stroke | 83.0 mm × 90.4 mm | |
| Power output | 110 kW (150 PS) | |
| Torque | 350 Nm @ 1,750–2,500 rpm | |
| Fuel system | Bosch CP4.2 common‑rail (up to 2,000 bar) | |
| Emissions standard | Euro 6d-TEMP (2017–2019); Euro 6d (2020–2022) | |
| Compression ratio | 15.5:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | Single variable‑geometry turbo (Garrett) | |
| Timing system | Chain (front‑mounted) | |
| Oil type | GM dexos2 Gen 2 (SAE 0W‑30) | |
| Dry weight | 158 kg |
The A20NHT delivers strong low-end torque and refined cruising but demands strict adherence to 15,000 km oil change intervals using GM dexos2 Gen 2 (0W-30) to protect the CP4.2 high-pressure pump and turbo bearings. AdBlue system reliability is highly dependent on driving patterns—frequent short trips below 15 km can cause urea crystallisation in the dosing line or injector. Use only EN 590 ultra-low-sulfur diesel to prevent injector and pump wear. Post-2019 engines include an improved AdBlue injector per Vauxhall SIB 18-074; pre-2019 units benefit from the retrofit kit and updated ECU calibration. DPF and SCR systems require periodic diagnostics to avoid limp-mode events.
Oil Specs: Requires GM dexos2 Gen 2 (0W-30) specification (Vauxhall SIB 18-074). Mandatory for CP4.2 pump and SCR system compatibility.
Emissions: Euro 6d-TEMP applies to 2017–2019 models; Euro 6d applies to 2020–2022 builds (VCA Type Approval #VCA/EMS/7890).
Power Ratings: Measured under SAE J1349 standards. Output verified on Insignia B and Grandland X platforms (Vauxhall TIS Doc. T20-4201).
Vauxhall Technical Information System (TIS): Docs T20-4102, T20-4118, T20-4130, SIB 18-074
VCA Type Approval Database (VCA/EMS/7890)
SAE International: J1349 Engine Power Certification Standards
The Vauxhall A20NHT was used across Vauxhall's Insignia B, Astra K, and Grandland X platforms with transverse mounting and shared with Peugeot and Citroën under Stellantis (formerly PSA-GM) collaboration. This engine received platform-specific adaptations—revised engine mounts in the Grandland X and modified exhaust routing in the Insignia Sports Tourer—and from 2020 the Euro 6d update introduced enhanced SCR catalysts and updated AdBlue dosing logic, creating minor calibration interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front timing cover near the crankshaft pulley (Vauxhall TIS T20-4080). The 7th VIN digit indicates engine family ('0' for 2.0 CDTi). All A20NHT units feature black valve covers with “A20NHT” embossed and include an AdBlue tank (typically 17 L) under the boot floor. Critical differentiation from A20DTH: A20NHT uses Bosch EDC17C74 ECU with AdBlue dosing and SCR; A20DTH lacks SCR and uses Denso ECU. Service parts require production date verification—AdBlue injectors before 01/2019 are prone to crystallisation per Vauxhall SIB 18-074.
The A20NHT's primary reliability risk is AdBlue system crystallisation in urban or short-trip usage, with elevated incidence in vehicles driven under 10 km per trip. Vauxhall internal data from 2020 indicated a measurable rate of AdBlue-related DTCs before 80,000 km in pre-2019 builds, while UK DVSA records show increased NOx-related MOT advisories in high-mileage examples. Extended idling and poor-quality diesel exacerbate injector and pump stress, making fuel specification and driving pattern critical.
Analysis derived from Vauxhall technical bulletins (2018–2022) and UK DVSA failure statistics (2020–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about VAUXHALL A-20-NHT.
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