Inspection and Diagnostic Process of ME1788 Syst...
1)Diagnostic Explanation
（1）Confirm it as“stable fault”before doing the following inspections,otherwise the diagnosis error may be caused.
（2）The“universal meter”mentioned below refers to“digital universal meter”,and the pointer multi-meter is forbidden in checking the electric ejection system circuit.
（3）When checking the vehicle with anti-theft system,and if there appears“Replace the ECU”in the column of“Following Procedure”,please remember to do the matching work for ECU after replacement.
（4）The Explanation for“Diagnostic Help”below:
①If the fault code can’t be eliminated,the fault belongs to stable fault;if it is the occasional fault,mainly check whether wire harness connector connection is loose or not.
②In maintenance process,do not ignore the effect of vehicle maintenance condition,cylinder pressure and mechanical ignition timing on the system.
③Replace ECU and then do the test.If the fault code can be eliminated now,then the fault exists in the ECU,if not,change back into the original ECU,repeat the process,do the inspection and maintenance work again.
2)DCT(Fault Code)Types and Count-measures
（1）Circuit Fault Type.
The usual description of fault code and the corresponding causes:
XXXX Circuit Fault—The circuit is open circuit.
Over Low Voltage of XXXX Circuit—Short circuit to the ground.
Over High Voltage of XXXX Circuit—Short circuit to the power.
At this moment,mainly check the wire connection from ECU to the sensor/actuator and the circuit characteristic of the sensor/actuator itself.
（2）Status Fault Type
The usual description of fault code and the corresponding causes:
Irrational XXXX Signal and XXXX Signal Fault—The signal exceeds the reference critical limit value or irrational mistake appears;
At this moment,mainly check the characteristic of the sensor/actuator itself and the physical characteristic of the signal generator.
（3）Specific Fault Type.
The fault code is compiled aiming at the specific fault content.
Mainly check whether the fault code belongs to the stable fault and make further inspection and maintenance according to the fault causes.
3)Typical DCT Diagnostic Process
When the fault light of vehicle’s engine managerial system illuminates constantly,connect the special decoder with the diagnostic connector so as to obtain the fault code,fault position,inspection and maintenance instructions through the decoder.This method is fast with high correction rate.
List the diagnostic process of a few common fault codes below,and check from the step 1 according to the serial No.and refer to the vehicle’s maintenance manual for the diagnostic process of the rest fault codes.
（1）Fault Code:P000A,Slow Response of Intake VVT Motion.(Table 4.11)(https://www.daowen.com)
Table4.11 Slow Response of Intake VVT Motion
（2）Table 4.12 Fault Code:P0031 Over Low Voltage of Upstream Oxygen Sensor Heating Control Circuit.
Table4.12 Over Low Voltage of Upstream Oxygen Sensor Heating Control Circuit
（3）Fault Code:P0036 Fault of Downstream Oxygen Sensor Heating Control Circuit(Table 4.13)
Table4.13 Fault of Downstream Oxygen Sensor Heating Control Circuit
（4）Fault Code:P0105 No Changes of Intake Air Pressure Sensor Signals.(Table.4.14)
Table4.14 No Changes of Intake Air Pressure Sensor Signals
（5）Fault Code:P0107 Over Low Voltage of Intake Manifold Pressure Sensor Circuit.(Table.4.15)
Table4.15 Over Low Voltage of Intake Manifold Pressure Sensor Circuit
（6）Fault Code:P0118 Over High Voltage of Cooling Liquid Temperature Sensor Signal(Table.4.16)
Table4.16 Over High Voltage of Cooling Liquid Temperature Sensor Signal
（7）Fault Code:P0304“Four Cylinders Misfire”Appears(Table.4.17)
Table4.17“Four Cylinders Misfire”Appears
（8）Fault Code:P0121 Irrational Signal 1 of Electronic Throttle Position Sensor(Table.4.18)
Table4.18 Irrational Signal 1 of Electronic Throttle Position Sensor
