Emissions breach likely to force two-wheelers into 'limp-home mode'

BS6 emissions norms are currently in force in India. The country is expected to move to BS7 from 2027, with new regime likely to bring tighter pollution controls and real-time monitoring requirements

The Ministry of Road Transport and Highways (MoRTH) and the two-wheeler industry are working on a mechanism under which a vehicle could be put into a “limp-home mode” if its emissions rise above the threshold prescribed under the second phase of Bharat Stage-VI (BS6) emission norms, government officials told Business Standard. Under the mode, the vehicle’s power or speed could be restricted, allowing the rider to reach a workshop while making normal use difficult.

 

The mechanism is being discussed as part of the on-board diagnostics (OBD) system, a vehicle’s built-in monitoring system that detects faults in emission-control components and alerts the rider when a malfunction pushes emissions beyond prescribed levels. 

 

The Society of Indian Automobile Manufacturers (Siam) has proposed introducing the mandatory “force repair” mechanism with the upcoming BS7 emission norms, saying significant development work is required to implement it. MoRTH, however, has rejected the request, saying the requirement is already part of the BS6 OBD-II framework and should not be deferred to BS7.

 

BS6 emissions norms are currently in force in India. The country is expected to move to BS7 from 2027, with the new regime likely to bring tighter pollution controls and real-time monitoring requirements.

 

Under BS6 OBD-II, applicable to vehicles manufactured from April 1, 2025, the threshold for petrol two-wheelers is 1,900 mg/km for carbon monoxide, 250 mg/km for non-methane hydrocarbons and 300 mg/km for nitrogen oxides.

 

Particulate matter (PM) has a threshold of 50 mg/km for petrol direct-injection engines.

 

These thresholds mark the emission levels at which the OBD system is required to detect and flag a sufficiently serious malfunction in the vehicle’s emission-control system. If such a malfunction pushes emissions above the prescribed limits, the proposed “force repair” mechanism would make it difficult to continue using the vehicle normally until it is repaired.

 

The matter has come up in discussions on OBD-II-B requirements under Automotive Industry Standard (AIS) 137, which lays down procedures for testing and monitoring vehicle emissions. MoRTH had asked Siam to come up with a proposal for addressing cases where emissions exceed the OBD threshold, officials said.

 

MoRTH, as well as Siam did not respond to Business Standard’s queries regarding the matter.

 

 Siam initially considered several options for what it calls a “force repair” measure -- a mechanism that would compel or strongly encourage the owner to get the vehicle repaired. These included restricting power, restricting speed, preventing the vehicle from starting, delaying the engine start, triggering a warning through the horn, escalating audible warnings, displaying an indication visible from outside the vehicle, blinking headlights and showing a zero fuel-level indication.

 

The industry body’s initial preference was to use an audible warning as the force-repair measure, officials said. However, following directions from the authorities, its two-wheeler group reconsidered the approach and agreed to examine stronger measures. It subsequently, officials said, narrowed the options to four: Restricting power, restricting speed, preventing the vehicle from starting, or delaying the engine start.

 

Siam’s assessment showed that restricting power and speed were technically manageable, had favourable cost implications and could be effective in enforcing repairs. However, the safety implications of these measures still needed to be reviewed. Preventing the vehicle from starting was considered less convenient, while delaying the engine start was considered technically manageable and relatively acceptable from a convenience perspective.

 

It is also examining the options from the perspectives of safety, the type of malfunction warning or “MIL (malfunction indicator lamp)”, protection against tampering and implementation costs. Siam has told MoRTH that significant development work would be required before such a system could be implemented, officials said.

 

Siam therefore proposed that the mandatory force-repair provision be made part of the upcoming BS7 emission norms, rather than being introduced under the existing BS6 OBD-II framework. MoRTH and the International Centre for Automotive Technology (ICAT), however, rejected the proposal, saying the requirement was already part of BS6 OBD-II.

 

The matter has not yet been finalised. MoRTH has asked Siam and ICAT to submit a concrete proposal and implementation plan at the next meeting. This means the exact form of the force-repair mechanism -- whether it will restrict power, limit speed, prevent starting or delay the start -- is still to be decided, officials noted.