Maintenance manual for sunray hfc4da1-2c china-IV diesel engines
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6. Malfunction indicator lamp
1) Overview
The malfunction indicator lamp is located on the instrument. In event of malfunction of engine control system units,
the engine malfunction indicator lamp will light up to
remind the driver for checking and service by the service
station as soon as possible.
2) Working Principle
The malfunction indicator lamp (MIL) is located on the
instrument panel and is directly powered by the voltage of
battery. The engine control unit (ECU) lights up the
malfunction indicator lamp by grounding the control circuit
of malfunction indicator lamp. When the ignition switch is
turned on but the engine is not started, the malfunction
indicator lamp (MIL) shall light up for 5s and then go out.
Functions of malfunction indicator lamp:
z The malfunction indicator lamp reminds the driver of the occurrence of malfunction. The vehicle shall be
serviced as soon as possible.
z The malfunction indicator lamp lights up during the test of the malfunction indicator lamp.
z If the diagnosis procedure requests to light up the malfunction indicator lamp, one diagnosis trouble code will be
stored.
Light-up of malfunction indicator lamp
z When the ignition switch is turned on but the engine is not started, the malfunction indicator lamp will light up
for 5s and then go out.
z The malfunction indicator lamp goes out after the engine is started.
z If any malfunction is detected by the self-diagnosis system, the malfunction indicator lamp will keep lighted up.
z If no malfunction is detected, the malfunction indicator lamp will go out.
3) Measurement analysis
4) Malfunction Mode
Short-circuit or open-circuit between engine control
unit to instrument circuit.
5) Troubleshooting:
Use Sunray special diagnosis instrument to check the
trouble code and determine the malfunction position.
Mainly check the circuit from engine control unit to
Malfunction indicator lamp
OBD indicator lamp
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