Page 75 - Foton Workshop Manual - Auman EST-M

Diagnosis - Diagnosis-fault diagnosis of electronic and electrical parts DI - 21

Application of diagnostic unit IN
1. DTC reading
Caution DI

● The fault shall be determined by the engine control system, and stored in engine control module
(ECM). The system fault can be current or historical fault. EG
● If the voltage of battery is too low, and the detection code of ECM fails to output normally, be sure to
first test the voltage of battery before the check, which shall be about 24V. TR
● In case of disconnecting the battery or ECM connector, the fault codes stored in ECM will be cleared.

● Read the fault codes of engine with a special checking tool. AX
● Before connecting or disconnecting the diagnostic unit, be sure to confirm that the ignition switch is in
“LOCK” position.
FR
ECM has a fault self-diagnosis function. Once the fault of electric injection system is detected, it will create

the corresponding fault code, which will be stored in the memory. It will enter into different failure protection
ST
policy as per the severity level of fault. In many cases, the failure protection policy can keep the

engine working at lower power. For a few of serious accidents, the failure protection policy will stop injecting
the fuel, and the engine will stop. BR
The fault codes can be read via a special diagnostic unit:
BW
a. After turning the ignition switch to “ON”, if the fault indicator lamp is on, it will indicate the system fault.

b. Connect the interface of special fault diagnostic unit to the diagnostic interface.
c. Read the fault code of diagnostic unit, i.e. “fault code” indicated on the diagnostic unit. EL

d. According to the fault causes corresponding to fault codes, check and repair the harness related to
corresponding part or replace the relevant part.
e. After removing the fault and clearing the original fault code with a fault diagnostic unit, read the fault code
procedures again, confirm no fault code, and bring it into service again.
2. Clearing of fault code
In case of confirming some accidental faults, it’s required to remove the fault code first. If any fault occurs to
the system, the fault code will exist until the fault is removed.

Connect the diagnostic unit, and clear the fault code stored in current control unit.
3. Reading of data flow
By reading the data flow indicated on diagnostic unit, any part needn’t be removed, because it’s allowed to
check the data values of switch, sensor and actuator, etc. Using the data stream read as the first step for trouble

shooting is a method to short the diagnosis time.

4. Action test

Action test is a self-learning process of component, which doesn’t need the removal of any part. It’s a learning

process to perform the test of relay or actuator and other special operations, etc.

DI-021