Background
In September 2019 the plaintiff purchased a motorhome built on a Fiat Ducato base vehicle manufactured by the defendant. The base vehicle is fitted with a 2.3-litre Multijet diesel engine certified to the Euro 6 emissions standard. The plaintiff alleged that the engine’s exhaust-gas recirculation (EGR) system is governed by a temperature-dependent control function — commonly called a “thermal window” (Thermofenster) — that constitutes an unlawful defeat device within the meaning of Article 3(10) and Article 5(2) of Regulation (EC) No 715/2007. She claimed that the correction factor applied to EGR control is reduced from 100 % to zero across a temperature band of 15 °C to 39 °C under normal road conditions, with further step-wise reduction below 20 °C down to 5 °C and outside the New European Driving Cycle (NEDC) test conditions.
The plaintiff sued for damages, seeking reimbursement of the purchase price less a use-based deduction plus interest (contingent on returning the vehicle), a declaration of the defendant’s liability for further losses, a declaration of the defendant’s default in accepting return of the vehicle, and indemnification from pre-litigation legal fees. The Regional Court (Landgericht Münster) dismissed the claim. The Higher Regional Court (Oberlandesgericht Hamm) dismissed the plaintiff’s appeal on 13 July 2023, holding that she had failed to plead the existence of a thermal window with sufficient specificity and that her submissions were internally inconsistent and speculative. The plaintiff then lodged a Nichtzulassungsbeschwerde (appeal against the refusal to grant leave to appeal on the merits) with the Federal Court of Justice (BGH).
The appellate hearing had taken place on 22 June 2023. Three days later, on 26 June 2023 — after the close of oral argument but before the OLG handed down its judgment — the BGH’s Sixth Civil Panel issued its landmark ruling in VIa ZR 335/21 (BGHZ 237, 245), which recognised a plaintiff’s right to claim the lesser “difference damage” (Differenzschaden) in diesel emissions cases rather than being confined to the “large” measure of damages (unwinding the contract). The OLG was aware of this ruling when it decided the case on 13 July 2023 but did not invite the plaintiff to adapt her pleadings accordingly.
The Court’s Holding
The BGH granted the Nichtzulassungsbeschwerde and, pursuant to § 544(9) of the Code of Civil Procedure (ZPO), quashed the OLG Hamm judgment in respect of the contested heads of relief — specifically the damages claim in the amount of €40,645.94 plus interest (Appeal Request 7a), the declaration of acceptance-delay (Appeal Request 7c), and the claim for indemnification of pre-litigation legal costs (Appeal Request 8) — and remanded those issues to the court of appeal for fresh proceedings including a new costs determination.
The BGH identified two independent violations of the plaintiff’s constitutional right to be heard under Article 103(1) of the Basic Law (Grundgesetz). First, the OLG assumed, without giving the plaintiff any notice, that she was pursuing only the “large” measure of damages, thereby depriving her of the opportunity to recalibrate her claim to the Differenzschaden framework established in VIa ZR 335/21. The BGH held that given the plaintiff’s obvious interest in obtaining at least the smaller, difference-based damages award, the OLG’s interpretation of her pleadings was implausible and the failure to issue a judicial notice (Hinweis) violated Art. 103(1) GG.
Second, the BGH held that the OLG had set the bar for pleading the thermal window unlawfully high. Under settled BGH case law, it suffices for a claimant to allege that EGR functions without restriction only within a software-defined temperature range and is reduced or switched off at ambient temperatures prevailing in Germany outside that range, resulting in excess NOx emissions. The parties here were not in dispute about the existence of the temperature-sensitive EGR function itself — the defendant’s own response confirmed it, differing only on the precise temperature threshold (the defendant said reduction begins at 9–12 °C intake temperature to prevent excessive soot build-up). Because the existence of the function was uncontested, the OLG had no basis to treat the plaintiff’s submissions as inconsistent or speculative, and its rejection of them violated Art. 103(1) GG.
Key Takeaways
- Where a pivotal BGH ruling on the measure of damages is handed down after the close of oral argument but before judgment, the appellate court must invite the plaintiff to amend her prayers for relief accordingly; failing to do so violates the constitutional right to be heard.
- In diesel thermal-window litigation, a plaintiff satisfies her pleading burden by asserting that EGR is reduced or deactivated at ambient temperatures typical in Germany outside a defined software range, causing excess NOx; she need not supply further technical detail when the dispute is only about the precise temperature parameters involved.
- Where the defendant’s own submissions confirm the existence of a temperature-dependent EGR control function — differing only on the trigger temperature — the court cannot dismiss the claim as unsubstantiated or speculative.
- The case is remanded to OLG Hamm to consider whether a Differenzschaden claim under § 823(2) BGB in conjunction with §§ 6(1) and 27(1) of the EG-FGV (national implementing regulation for Regulation (EC) No 715/2007) is available to the plaintiff.
Why It Matters
This decision reinforces the BGH’s consistent line of authority — most recently in VIa ZR 909/23 (October 2025) and VIa ZR 954/23 (January 2026) — requiring lower courts to issue timely procedural notices when mid-litigation precedent shifts the legal landscape in diesel emissions disputes. Appellate courts that silently maintain a restrictive interpretation of a claimant’s pleadings, without affording an opportunity to adapt to new BGH guidance, risk reversal on constitutional grounds alone.
The ruling also consolidates the plaintiff-friendly pleading standard for thermal-window allegations that the BGH has been refining since its September 2024 decision in VIa ZR 347/22 and its cluster of 2026 decisions (VIa ZR 1154/23, VIa ZR 1055/23, VIa ZR 482/23, VIa ZR 662/23). For practitioners handling Euro 6 diesel emissions claims involving Fiat Ducato or similar multi-brand platforms using the Multijet engine family, this decision signals that a manufacturer’s acknowledgment of any temperature-dependent EGR management — even framed as a pro-engine justification — will generally be treated as conceding the factual predicate of a defeat-device claim.