Engine JAC HFC4DA1-2C. Service manual — part 25

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

Maintenance manual for sunray hfc4da1-2c china-IV diesel engines

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instrument circuit and determine whether there is short-circuit or open-circuit between circuit and the grounding wire,
whether there is short-circuit or open-circuit to power supply, and whether the circuit is consistent with the given pin
definition.

7. Diagnosis interface

1) Overview

The diagnosis interface is located in the electric box beneath the driver’s side instrument panel and is used to connect
the special diagnosis instrument.

2) Working Principle

This is one data transmission interface for communication with ECU and is one standard OBD interface.

3) Measurement analysis

4) Malfunction Mode

Short-circuit or open-circuit between engine control unit and diagnosis interface.

Working failure of engine control unit.

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 diagnosis interface circuit and determine whether there is short-circuit or
open-circuit between circuit and the grounding wire, whether there is short-circuit or open-circuit to power supply,
and whether the circuit is consistent with the given pin definition.

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Chapter IV Engine Diagnosis

Section I.

Precautions

1. Removal/Installation Requirements for Electronic Control Unit (ECU):

z Remove the controller before welding or baking finish;

z When removing the controller, turn off the ignition switch and disconnect the battery from the system at the same

time, in order to avoid damaging the ECU.

z It is not allowed to remove power cord from the battery when the engine or the electrical system is working.

z Large-current equipment such as charger is not allowed to be directly connected to the starting motor.

z Note: The ambient temperature of ECU should not be greater than 75 degree.

2. Cleaning Requirements:

Please observe the following rules before the operation of fuel supply system and fuel injection system:

z The removed components should be placed at clean field and properly covered by the cloth other than fiber type

(cotton cloth or gauze cloth)

3. All types of harness connectors and the connector for diagnostic instrument should be
connected and disconnected only when the ignition switch is turned off:

z When measuring the power voltage or ground wire of the ECU, please ensure the wiring sequence and method is

correct.

z Disconnecting the power cord or the ground wire of the battery from the system or removing ECU harness

connector will result in the loss of diagnosis and self-learning information stored in ECU. (If the vehicle model is
different, the time of retaining Pleas of the ECU is also different after the loss of power.)

4. Please pay attention to the following points when maintaining the fuel supply system (fuel
supply pipe, fuel pump and fuel injection system):

z Please be very careful during installation/removal of fuel pump on the fuel tank with fuel.

z Prepare proper materials around the fuel tank opening to absorb a lot of fuel leaked from it timely..

z Avoid the fuel contacting your body.

z Thoroughly clean the part and its surrounding before loosening a connector.

z Please prevent any fuel from splashing from the loose part and place a rug around the connector.

z If the disassembled parts could not be timely repaired or properly treated, store the parts properly.

z Take the spare parts out of the package only when they are needed to be installed. Do not use unpacked spare

parts and the spare parts in severe damaged package

z Do not damage the O-ring of return pipe when assembling fuel injector return pipe. Coat a little diesel oil on the

O-ring for assembling convenience.

z Do not use the compressed air and do not move the vehicle after the fuel supply system is disassembled.

5. Safety Measures

To prevent the maintenance technicians from being injured and the fuel and ECU being damaged, please pay attention

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to the following points:

z If the engine is working or at the starting speed, it is not allowed to check for any single cylinder failure by the

way of disconnecting the fuel injector harness.

z If the engine needs to be dragged but not started by the starter, such as when you check the engine cylinder

pressure, the harness plug should be disconnected from the crankshaft position (engine speed) sensor and
camshaft position (phase) sensor. After inspection, all sensors should be well connected and system DTCs should
be cleared by using the special diagnostic instrument for JAC commercial vehicles.

z It is not allowed to touch the engine gear train and rotating parts when the engine is at high speed;

z When the engine reaches normal operating temperature, the coolant temperature and pressure of cooling system

is very high; therefore, stop the engine and let the cooling system fully cool down if it is needed to repair the
engine cooling system.

z If the engine compartment relevant maintenance is necessary to be conducted in repairing engine fuel system,

please do it after the engine compartment is fully cooled down.

z Don’t touch the engine cooling fan at any time when the system is normally electrified, for the cooling fan is

likely to be started suddenly.