Engine JAC HFC4DA1-2C. Manual — part 34

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

135

− Poor contact between terminal and wire

Check the harness for any damage. If the harness appears normal, observe the ECT indication on the diagnostic tool
while moving relevant connector and harness of ECT sensor. If the ECT indication changes, there must be failure in
that part. If the DTC won’t appear again, the fault record data can be used for determining the self-diagnostic code and
the running mileage after the previous setting can be used for determining the occurrence frequency of that condition,
which can facilitate the troubleshooting for overheating.

After the engine is started, the engine coolant temperature shall increase steadily to about 90°C (194°F) and then
become stable after the thermostat is disconnected.

Terminal ECU

A37

Signal terminal of ECT sensor

A50

Ground terminal of ECT sensor

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

136

Fault Tree:

Check the sensor connection.

Connector fault

Repair accordingly.

Repair accordingly.

Replace the sensor.

Detect the sensor resistance. (Is it consistent with

the vehicle condition?)

Fault of sensor resistance

Fault of ECU connector

Check continuity and insulating property.

Electrical fault

Repair the harness.

Replace the component.

Does the problem still exist?

Get the Technical Support.

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

137

5.

DTC

P0122

The output voltage of accelerator pedal potentiometer 1 is below the lower limit.

P0123

The output voltage of accelerator pedal potentiometer 1 is above the upper limit.

P0222

The output voltage of accelerator pedal potentiometer 2 is below the lower limit.

P0223

The output voltage of accelerator pedal potentiometer 2 is above the upper limit.

Fault Description: The accelerator pedal assembly consists of two accelerator pedal position (APP) sensor. The APP
sensors are installed on the pedal assembly and are not repairable. The APP sensor shall supply a signal voltage that
changes with the accelerator pedal position. The ECU shall supply an individual 5V reference voltage circuit and a
low level reference voltage circuit to each APP sensor. With the pedal depressed, the signal voltage of APP sensor 1
shall increase, viz. increasing from about 0.7V (at the released position) to above 4V (at the fully depressed position).
With the pedal depressed, the signal voltage of APP sensor 2 shall increase, viz. increasing from about 0.3V (at the
released position) to above 2V (at the fully depressed position).

APP sensor 1 and 2 are installed in the accelerator pedal assembly. Each one consists of the following circuits:

z A 5V reference voltage circuit

z A low reference voltage circuit

z A signal circuit

With those circuits, the APP sensors can provide the signal voltage that is proportional to the displacement of
accelerator pedal to the ECU. Two processors, located in the ECU, are adopted to monitor the data of throttle actuator
control system. Each signal circuit shall provide the signal voltage that is proportional to the displacement of
accelerator pedal to two processors. Those two processors shall monitor each other to verify whether the indicated
value of pedal position is correct or not. The test method of ECU is: making the signal of APP sensor 2 lower
instantaneously to see if the signal of APP 1 is also made lower.

Diagnosis Hint: During testing, if it is necessary to detect the ECU harness connector or component harness
connector, a diagnostic connector should be adopted to test the adapter component.

If several DTCs appear simultaneously, please check if the signal circuits for APP sensor 1 and 2 are short to each
other.

Electronic

accelerator pedal

Power supply of sensor

1

Ground of sensor 1

Signal 1

Power supply of sensor

2

Signal 2

Ground of sensor 2

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

138

Terminal ECU

K28

Power supply terminal of APP sensor 1

K81

Signal terminal of APP sensor 1

K67

Ground terminal of APP sensor 1

K22

Power supply terminal of APP sensor 2

K60

Signal terminal of APP sensor 2

K58

Ground terminal of APP sensor 2