During the production of a vehicle, the following parameters are checked for compliance with the required standards:
- average emissions of toxic components after cold start;
- carbon monoxide emissions at idle;
- crankcase emissions;
- toxic emissions due to evaporation.
When operating a vehicle, compliance with toxicity standards laid down by the vehicle design, subject to the fulfillment of the regulated maintenance periods, must be valid for a mileage of 80,000 km or for 5 years.
The EOBD system is responsible for ensuring that the vehicle meets the required emission standards in accordance with EURO III (European On-Board Diagnostics). The EOBD system is designed to warn the driver via the engine diagnostic indicator about any faults that may affect toxicity. The EOBD system is software designed to monitor and is embedded in the electronic engine control unit. The system has two main functions:
- detects faults in vehicle emission control equipment;
- alerts the driver to faults that could cause emissions limits to be exceeded so that the vehicle can be repaired.
The engine control unit constantly monitors the following elements, which play an important role in toxicity management:
- misfires;
- catalytic converter efficiency;
- oxygen sensor status;
- any node or system (air injection, EGR system, automatic transmission), the failure of which may lead to exceeding the threshold value of permissible toxic emissions;
- continuity of the electromagnetic valve circuit for purging the fuel vapor absorber tank.
Permissible limits are set for each toxic substance.
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In case of exceeding the limit established by the standards (malfunctions) the engine diagnostic indicator lights up - this error is remembered.
The engine diagnostic indicator indicates a malfunction in one of the components or systems related to toxicity if this malfunction leads to an increase in toxic emissions and the emission level exceeds the established standards.
Misfires that threaten to damage the catalytic converter cause the check engine light to flash. The check engine light comes on when there is a risk of engine failure or the safety of the vehicle occupants is at risk.
Illumination occurs at the end of 3 consecutive cycles: engine start, vehicle movement during which a possible malfunction is detected, and engine stop.
The diagnostic indicator switches off after 3 consecutive driving cycles during which the monitoring system responsible for activation no longer records any faults, the error becomes temporary. The computer can erase a temporary error if the error has not recurred within 40 warm-up cycles.
A warm-up cycle is the amount of time the vehicle is running for the coolant temperature to rise to at least 22°C from the moment the engine is started and reach a minimum of 70°C.
Temporary errors can also be erased using the DIAG 2000 diagnostic tool.
Access to the codes of recorded errors is open to any specialist who has a standardized diagnostic device SCANTOOL.
Access to diagnostic modes includes the following actions:
- mode 01 - reading the number of error codes and engine speed;
- mode 02 - reading a fixed signal packet (related variables);
- mode 03 - reading error codes;
- error code mode;
- 04 - erase.