Implementation of a new ECU diagnostic strategy
On an ongoing basis, only diagnostics of passes are carried out. The remaining components that affect the toxicity of exhaust gases are tested only once per trip (diagnostics are not performed all the time). However, this sequence of checks does not always take place. Checks are made while driving if certain conditions are met:
- temperature condition;
- speed condition (threshold, stability.);
- expiration of the time delay after starting the engine;
- engine operating conditions (intake manifold pressure, rpm, throttle opening angle.).
The on-board diagnostic system is an additional means of detecting common electrical faults. The system ECU must provide:
- burning with constant light (or flashing light for some malfunctions) signal lamp of the on-board diagnostics system;
- memorization of malfunctions detected by the on-board diagnostics system.
Impact on diagnosis and repair
To prevent the OBD warning light from illuminating after the vehicle is returned to the customer, special care must be taken when working on the vehicle.
Some defects may only appear in motion after programming the correction parameters: checking the quality of the repair is mandatory.
On the other hand, the complexity of the system makes it necessary to find out from the customer the conditions under which the warning light came on. This information will help diagnose problems faster.
The conditions for the occurrence of a malfunction are recorded in the memory of the computer.
Note. Any electrical failure that exceeds the toxicity threshold will cause the OBD warning light to come on.
Functional diagnostics taken into account by the on-board diagnostics system:
- diagnosis of mixture misfires that are destructive to the catalytic converter;
- diagnostics of misfires of the mixture, leading to an increase in the toxicity of exhaust gases;
- diagnostics of the upper and lower oxygen sensors;
- catalytic converter diagnostics.
Note. Misfire diagnosis is a priority over other troubleshooting. Shift misfires are monitored almost continuously after vehicle driving conditions begin to be met.
Attention! At the end of each test, never switch off the ignition before reading the result on the scan tool. Turning off the ignition leads to incorrect interpretation of the results and loss of information about «performed diagnostics».