The Honda IMA (Integrated Motor Assist) is a parallel hybrid system, not a standalone engine, introduced in 1999 and produced until 2015. It combines a small electric motor/generator, integrated between the petrol engine and transmission, with a 144V nickel-metal hydride (NiMH) battery pack. This system provided modest power assist and regenerative braking, enhancing fuel economy without requiring external charging.
Fitted to models such as the Insight (ZE1, ZE2), Civic Hybrid (ES, FA, FG), and CR-Z (ZF1), the IMA was engineered for maximum fuel efficiency in urban and highway driving, using Honda's lean-burn petrol engines as its base. Emissions compliance was met through ultra-lean combustion and the hybrid system's ability to shut off the engine at stops, allowing compliance with Euro 4 and later Euro 5 standards.
One well-documented reliability concern is battery pack degradation, particularly in hot climates or with high mileage, addressed in Honda Service Bulletin A09-045. The bulletin details revised battery cooling duct routing and software updates to optimize charge/discharge cycles, implemented in vehicles produced after 2011.
Production from 1999–2015 meets Euro 4 and Euro 5 emissions standards depending on model year and market (EU Regulation (EC) No 715/2007, as amended).
The Honda IMA system is a mild parallel hybrid architecture engineered for compact cars (1999-2015). It combines a petrol engine with an electric motor to deliver enhanced fuel economy through engine stop-start and torque assist. Designed to meet Euro 4 and Euro 5 standards, it prioritizes low emissions and efficiency for daily commuting.
| Parameter | Value | Source |
|---|---|---|
| System Type | Parallel Hybrid (Mild Hybrid) | |
| Electric Motor | DC Brushless Motor (10-20 kW assist) | |
| Battery Type | Nickel-Metal Hydride (NiMH) | |
| Battery Voltage | 144V | |
| Petrol Engine Base | Varies (e.g., L13A, L15A, R18A) | |
| System Power Output | Varies by model (e.g., 85-120 kW combined) | |
| Regenerative Braking | Yes | |
| Emissions standard | Euro 4 / Euro 5 (model dependent) | |
| Cooling system | Air-cooled battery pack | |
| Transmission | CVT (Continuously Variable Transmission) | |
| Oil type (Engine) | Honda 0W-20 or 5W-30 (spec. HTO-06) | |
| System Weight (approx.) | 65-85 kg (including battery) |
The IMA system provides seamless engine stop-start and torque assist for improved fuel economy but requires specific maintenance for the hybrid components. The NiMH battery pack is susceptible to heat degradation; ensuring the cooling ducts are unobstructed is critical. The system relies on the 12V auxiliary battery for control logic; a weak 12V battery can cause IMA system faults. Software updates per Honda SIB A09-045 can optimize battery life. The CVT transmission requires its specific fluid and regular changes.
Oil Specs: Requires Honda 0W-20 or 5W-30 (spec. HTO-06) for the internal combustion engine, depending on model (Honda Owner's Manual).
Emissions: Meets Euro 4 (early models) or Euro 5 (later models) standards depending on production year and market (EU Regulation (EC) No 715/2007, as amended).
Power Ratings: Combined system output varies by model and is not a simple sum of engine and motor power (Honda TIS Doc. IMA-A26015).
Honda Technical Information System (TIS): Docs IMA-A24680, IMA-A25142
EU Regulation (EC) No 715/2007 (Emissions)
Honda Service Information Bulletin (SIB A09-045)
The Honda IMA system was used across Honda's Global Hybrid platforms with transverse mounting. This system received platform-specific adaptations-different motor sizes for the Insight vs. Civic Hybrid-and from 2011 the CR-Z introduced a sportier calibration with a 6-speed manual option, creating software and component differences. All adaptations are documented in OEM technical bulletins.
Locate the "IMA" badge on the rear of the vehicle. The hybrid battery pack is located under the rear cargo floor or behind the rear seat. The 8th VIN digit for IMA-equipped models is typically 'Z' or 'J'. Visually, the engine bay will have an orange high-voltage cable running from the engine to the transmission. Critical differentiation from e:HEV: IMA systems use a 144V NiMH battery and a single motor integrated into the transmission bellhousing, while e:HEV uses a higher-voltage lithium-ion battery and two separate electric motors. Service requires specialized hybrid training due to high-voltage components.
The IMA system's primary reliability concern is battery pack degradation, with Honda's internal data indicating a higher failure rate in vehicles operated in hot climates or with over 150,000 km. UK DVSA MOT statistics show battery-related warning lights as a common advisory item for these models. Ensuring the 12V battery is in good health and the IMA battery cooling system is unobstructed is critical for long-term system function.
Analysis derived from Honda technical bulletins (1999-2015) and UK DVSA failure statistics (2010-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about HONDA IMA.
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