Page 67 - Foton Workshop Manual - Auman EST-M

Diagnosis - Diagnosis-fault diagnosis of electronic and electrical parts DI - 13

Intermittent fault IN

If an intermittent fault exists, perform the following diagnostic procedures:
Warning DI

● If any intermittent fault occurs, this fault will be automatically removed in many cases (the part or
circuit will recovers to its normal function under no interference). It should be understood that the EG
conditions complained by the client may not occur in case of detecting DTC. It’s also known that the

most normal reason of intermittent fault is usually poor electric connector. Therefore, the state is not
clear when any fault occurs, so the circuit check may not point out the detailed fault area as a standard TR
part of diagnostic procedures.
● In this case, it’s required to know the detailed fault occurrence conditions for the client, ask the AX
vehicle owner about detailed driving conditions, climate conditions, frequency and fault symptoms,
analyze them, then simulate the same or similar conditions and environment when the fault occurs to FR
this vehicle, and confirm whether the fault symptom is caused by vibration, temperature or other
factors.
ST
● Regardless of rich experiences and exquisite skills of repairman, he or she certainly neglects some
important factors in case of analyzing the fault without verification, thus he or she may make a wrong
BR
guess, resulting in wrong repair or repair failure.

1. Vibration method
BW
When the vibration is recognized as main fault cause, check the connector and components to

determine whether the fault symptom exist. Simulate the fault as per the following method:
EL
a. Connector: shake the connector lightly in vertical or horizontal direction, check whether the wire harness

connector for connecting the connector and corresponding parts is loosened, its terminals are dirty, rusted,
corroded or bent; whether its contact is loosened due to terminal extension.
b. Harness: shake the wire harness lightly in vertical or horizontal direction, and thoroughly check the
connection and vibration areas of connector and harness of engine/cab instruments for disconnection.
c. Relay, part and sensor: gentle hand patting is required because the sensor, relay or part is recognized as the
fault cause. Check the sensor, relay or part for failure, but the relay can’t be forcibly patted on, otherwise it
may cause the broken circuit of relay.

2. Heating method

When the fault is caused by some suspected area, it’s possible to cause the fault to heat the component with an

electric hair drier or similar device, so as to check whether the fault occurs.

Warning

Its heating temperature shall not exceed 60℃ (its heating temperature can be limited by touching the

elements by hands). Don’t heat the electronic control module.

3. Water injection method

When the fault occurs on rainy day or in wet climate, spray water on the vehicle to check whether the fault

occurs.

DI-013