Engine JAC HFC4DA1-2C. Manual — part 20

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

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4) Malfunction Mode

z Short-circuit or open-circuit of sensor;

z Distorted, error, and suspicious signal;

z Unstable sensor signal;

z Sensor signal is out of range.

5) Troubleshooting

Use diagnosis instrument to check the trouble code and determine the malfunction position. Mainly check whether the
sensor is installed in place and whether the clearance is normal, check the sensor circuit whether there is short-circuit
or open-circuit to grounding wire, check whether there is short-circuit or open-circuit to the power supply, and check
whether the circuit is consistent with the given pin definition.

3. Pressure difference sensor

1) Overview

z The pressure difference sensor is functioned to real-time monitor the pressure drop of the POC and determine

whether the after-treatment system is working normally. The pressure at two ends of the POC is introduced via
two pressure ports of the sensor and then the sensor converts the measurement into voltage value and feeds back
to control unit. This can not only guarantee the sufficient oxidization of grains, but also prevent the blockage of
catalytic converter.

z The pressure difference sensor and the POC are connected via stainless steel pipe and high temperature rubber

hose. The pressure is introduced via stainless steel pipe, which is at least 250mm in length, from two sides of
POC and then is led to the pressure difference sensor via high temperature rubber hose, which is capable of
enduring more than 150ºC.

2) Working Principle

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

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3) Test analysis

Wiring terminals: 1 - +5V, 2 – Signal +, 3 – Grounding

3. Turbocharger pressure sensor

1) Overview

The turbocharger pressure sensor is connected to the
intake pipe and is functioned to measure the absolute
pressure of the intake pipe. This sensor is composed of
one pressure unit with two sensing units and one
evaluation circuit chamber. The sensing units and
evaluation circuit are mounted on common ceramic
substrate. Each sensing unit incorporates one horn-shaped
diaphragm embodying the benchmark capacity for
determination of internal pressure. The diaphragm moves
towards large or small open extent as a function of
charging pressure. The pressure sensitive resistor is
mounted on the diaphragm surface, of which the resistance
varies under the application of pressure. These resistors are
connected to form a resistor bridge. Therefore, any
movement of the diaphragm will change the balance of
resistor bridge, namely the voltage of the resistor bridge is
one measurement of turbocharger pressure. The evaluation
circuit is functioned to amplify the bridge voltage and
compensate the linear variation of temperature influence
and pressure characteristic. The output signal of evaluation
circuit is transmitted to ECU and then the turbocharger
pressure is obtained by means of the programming
characteristic curve.

z The temperature sensor incorporates one negative

temperature coefficient (NTC) thermistor that is
connected in the voltage division circuit of 5V power
supply.

z The voltage drop on the resistor is inputted to the ECU via one analog and one digital converters (ADC), which

is one measurement for evaluating the temperature. The ECU micro-processor embodies one characteristic curve,
which defines the temperature as a function of given voltage.

z It’s installed on the pressure stabilizing chamber of intake manifold and take the priority to measure the pressure.

z Wiring terminals: 1 – Grounding, 2 – Temperature signal, 3 – +5V, 4 – Pressure signal.

2) Working Principle

The turbocharger pressure sensor is connected in the intake pipe and is capable of measuring the absolute pressure of
intake pipe at 0.5~3bar. This sensor is composed of one pressure unit with two sensing units and one evaluation circuit
chamber. The sensing units and evaluation circuit are mounted on common ceramic substrate. Each sensing unit
incorporates one horn-shaped diaphragm embodying the benchmark capacity for determination of internal pressure.
The diaphragm moves towards large or small open extent as a function of charging pressure. The pressure sensitive

Pressure

difference

sensor

5V power supply

Pressure difference signal

Earthing

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resistor is mounted on the diaphragm surface, of which the resistance varies under the application of pressure. These
resistors are connected to form a resistor bridge. Therefore, any movement of the diaphragm will change the balance
of resistor bridge, namely the voltage of the resistor bridge is one measurement of turbocharger pressure. The
evaluation circuit is functioned to amplify the bridge voltage and compensate the linear variation of temperature
influence and pressure characteristic. The output signal of evaluation circuit is transmitted to ECU and then the
turbocharger pressure is obtained by means of the programming characteristic curve.

The voltage drop on the resistor is inputted to the ECU via one analog and one digital converters (ADC), which is one
measurement for evaluating the temperature. The ECU micro-processor embodies one characteristic curve, which
defines the temperature as a function of given voltage.

3) Measurement analysis
Wiring terminals: 1 – Grounding, 2 – Temperature signal, 3 – +5V, 4 – Pressure signal.

4) Malfunction Mode

The light-up of the engine malfunction indicator lamp indicates the presence of malfunction in the engine system and
it’s necessary to diagnose with diagnosis instrument. Use Sunray special diagnosis instrument to communicate with
ECU of electronic injection system and read out the malfunction data in the ECU.

5) Troubleshooting

Use Sunray special diagnosis instrument to check the trouble code and determine whether there is short-circuit or
open-circuit between circuit of malfunction position 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.

4. Thermal diaphragm air flowmeter

1) Overview

z The thermal diaphragm airflow sensor is one air mass sensor fitted with

logic output. To obtain the air flow, the sensor diaphragm on the sensor is
heated by the heating resistor installed in the middle and the temperature
distribution on the diaphragm is measured by the temperature resistors
installed paralleling with the heating resistor. The air flow passing through
the sensor changes the temperature distribution on the diaphragm to cause
resistance difference between two temperature resistors. The resistance
difference depends on the direction and flow rate of the airflow so that the
airflow sensor has high requirements over the flow rate and direction of the
airflow. The sensor manufactured by micro-machinery features small size,
low thermal capacity, and <15ms response time.

z The sensor is internally fitted with intake temperature sensor to measure the

intake temperature.

z The air flowmeter is installed at the port of the air cleaner.

z Wiring terminals: 1. +12V power supply; 2. Grounding; 3. Air temperature signal; 4. Airflow rate signal.

Turbocharger pressure

and temperature

sensor

Grounding

5V power supply

Intake pressure signal

Intake temperature signal

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

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2) Working Principle

This sensor is composed of two sensors, namely airflow sensor and intake temperature sensor, and is installed on the
intake hose after the air cleaner. This type of sensor requires that there shall be free of air leakage from the sensor to
the engine combustion chamber, or it will lead to unstable idling of engine or even engine flameout.

The airflow sensor integrates some micro-electronic units on a ceramic substrate. When the engine is working, the
diaphragm will be heated. The intake airflow passing through the diaphragm will take away the heat and the
Wheatstone bridge integrated on the diaphragm will increase the current to supplement the heat loss, which leads to
the variation of electric signal. This signal is transmitted to the engine control unit ECU, based on which the ECU can
obtain the load variation of the engine and thus control the fuel injection pulse width.

The intake temperature sensing unit is one negative temperature coefficient (NTC) thermistor. The sensor installs two
same sensing units on two sides of the thermal diaphragm. When the intake airflow flows through the diaphragm, the
temperature of the temperature sensing unit on the front of diaphragm is slightly lower than that of temperature
sensing unit on the rear. Based on this characteristic, the ECU can judge the direction of airflow.

3) Measurement analysis

Wiring terminals: 1. +12V power supply; 2. Grounding; 3. Air temperature signal; 4. Airflow rate signal.

4) Malfunction Mode

The subsequent electronic device of the air flowmeter in the ECU can judge the malfunctions such as open-circuit or
short-circuit of internal circuit and connecting circuit of air flowmeter and the damage of sensor. Upon the detection
that the output signal of the sensor is out of its output characteristic curve, the ECU will judge as malfunction of
sensor.

5) Troubleshooting

When the airflow sensor is failed, the engine cooling fan will run at high speed for one period after the ignition key is
turned to Off. For instance: When the airflow rate is higher than the upper limit of airflow or less than the lower limit
of airflow, the ECU will judge as malfunction of sensor (Though the intake airflow rate is less than lower limit
(closing to zero) at the start of the vehicle, the ECU can judge the start condition) and at the same time light up the
engine malfunction lamp and work under malfunction mode.

Air flowmeter

Voltage output V

Common rail

pressure