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
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