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17-5
(2) Exhaust gas recirculation valve control function
• Based on inputs from various sensors, the engine electronic control unit determines the degree of opening of the
exhaust gas recirculation valve and sends corresponding control signals to the exhaust gas recirculation electron-
ic drive unit to activate the exhaust gas recirculation magnetic valve.
In the case of black smoke emission or engine speed instability, which may occur when the engine is heavily load-
ed or lightly loaded, or when the auxiliary brake is operating, the engine electronic control unit stops exhaust gas
recirculation valve control.
(3) Fault diagnosis function
• While the starter switch is in the ON position, the engine electronic control unit continuously monitors exhaust gas
recirculation electronic drive unit, the sensors and other control elements for faults. In the event that the engine
electronic control unit finds a component faulty, it causes an indication to be made in the meter cluster to alert the
driver. At the same time, it memorizes the fault location in the form of a diagnosis code.
• While the engine is running, the exhaust gas recirculation electronic drive unit continuously monitors the status of
communication with the exhaust gas recirculation magnetic valve and engine electronic control unit. When the ex-
haust gas recirculation electronic drive unit detects a fault, it sends the information to the engine electronic control
unit.
• While the control during fault is taking place, the system’s functionality is limited to ensure vehicle and driver safe-
ty. It is possible to read the memorized diagnosis code using a Multi-Use Tester or from flashing of the warning
lamp.
• Diagnosis codes shown by the Multi-Use Tester and those indicated by flashing of the warning lamp are different.
• The Multi-Use Tester is capable of showing more detailed diagnosis codes.
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