During the production of a car for compliance with the required standards, the following parameters are checked:
- average emissions of toxic components after cold start;
- carbon monoxide emissions at idle;
- crankcase emissions;
- toxic emissions due to evaporation.
When operating a car, compliance with the toxicity standards laid down by the design of the car, provided that the regulated maintenance periods are met, must be valid for a mileage of 80,000 km or for 5 years.
The EOBD system is responsible for meeting the required emission standards corresponding to EURO III (European system of on-board diagnostics). The EOBD system is designed to alert the driver, via the Engine Diagnostics Warning Light, of all malfunctions that may affect emissions. The EOBD system is a software designed to control and embedded in the electronic engine control unit. The system has two main functions:
- determines malfunctions of vehicle equipment designed to reduce toxicity;
- Alerts the driver of malfunctions that could lead to exceeding the toxicity limits so that he can repair the vehicle.
The engine control unit constantly monitors the following elements that play an important role in emissions management:
- misfires;
- efficiency of the catalytic converter;
- condition of oxygen sensors;
- any node or system (air injection, EGR system, automatic transmission), the failure of which may lead to the excess of the threshold value of permissible toxic emissions;
- continuity of the solenoid valve purge of the tank of the fuel vapor absorber.
Permissible limits are set for each toxic substance.
In case of exceeding the limit established by the norms (malfunctions) the engine diagnostic indicator lights up - this error is stored.
The engine diagnostic warning light indicates a malfunction of one of the components or systems related to toxicity, if this malfunction leads to an increase in emissions of toxic substances, and the level of emissions exceeds the established limits.
Misfires that threaten catalytic converter failure cause the engine diagnostic warning light to flash. The engine diagnostic warning light comes on when there is a risk of engine failure or a safety hazard for the vehicle's occupants.
Ignition occurs at the end of 3 consecutive cycles: starting the engine, driving the car, during which a possible malfunction will be recorded, and stopping the engine.
The diagnostic indicator turns off after 3 consecutive driving cycles, during which the monitoring system responsible for activation has no longer detected any malfunctions, the error becomes temporary. The computer can clear a temporary error if the error does not reoccur within 40 warm-up cycles.
The warm-up cycle is the length of time the vehicle has been 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 cleared using the DIAG 2000 diagnostic tool.
Access to the recorded error codes is open to any specialist who has a normalized SCANTOOL diagnostic tool.
Accessing diagnostic modes includes the following actions:
- mode 01 - reading the number of error codes and engine speed;
- mode 02 - reading a fixed signal (related variables);
- mode 03 - reading error codes;
- error code mode;
- 04 - erasing.