Chery A15. Manual - part 33

 

The ECU can indirectly control the purge airflow 
through controlling the charging time of the carbon 
canister solenoid valve based on the signals provided 
by various sensors of the engine. 

Fault diagnosis: The ECU doesn’t have the function of 
self-diagnosis for the carbon canister control valve, but 
has the function of self-diagnosis for the driving stage 
of control valve of carbon canister. If the driving state 
of the control valve of carbon canister is short or 
overloaded to the battery voltage, short to ground or 
open, the basic memory of the closed loop control of 
fuel quantity will be closed, the memory of idling air 
demand quantity will be closed and the memory data at 
that time is valid. The common malfunctions of engine 
are unstable idling or excessive high idle speed under 
the malfunction of the solenoid valve of carbon 
canister. 

Pins: 

1# pin is connected to the 87# pin on output terminal of 
the main relay; 
2# pin is connected to the 46# pin of ECU. 

Troubleshooting:  The blockage and crack of the 
carbon canister will result in the increase of air intake. 

 

※  Steel fuel distribution pipe assembly 

Function: Store and distribute the fuel and provide a 
relative stable pressure for the fuel injection system so 
as to achieve the uniform fuel supply pressure and 
quantity for each cylinder and stable operation of 
engine. 

Structure:  The fuel distribution pipe assembly is 
comprised of fuel distribution pipe (KVS-S) and fuel 
injector (EV). 

Installation requirement: The connection of fuel pipe 
and rubber hose shall be fastened by clamp. The model 
of the selected clamp shall match to the rubber hose to 
ensure the seal connection between the fuel pipe and 
the rubber hose. 

Fault diagnosis: There is seldom possibility for the 
malfunction occurrence in the main fuel supply pipe. 
Most of the malfunctions, which result in the leakage of 
the fuel system, are caused by poor assembly, so proper 
note shall be paid during installation that any used 
O-oil seal shall not be used again and appropriate 
lubricant is allowed to be painted during assembly. 

 

Carbon canister control valve 

Carbon canister control valve

Circuit diagram of the solenoid valve
of the charcoal canister TEV-2

 

G-20

 

BASIC PRINCIPLE OF FAULT DIAGNOSIS FOR ELECTRONIC 

FUEL INJECTION SYSTEM 

·RECORD OF MALFUNCTION INFORMATION 

The electronic control unit consistently monitors the operations of sensors, actuators, 
related circuits, malfunction alarm lights, voltage of battery and so on, even the 
operation of the electronic control unit itself, as well as carries out the examination on 
reliabilities of the signals output by the sensors, driving signals of actuators, and 
internal signals (such as oxygen closed loop control, knock control, idle speed control, 
battery voltage control and etc.). Once it is found that there is a malfunction in some 
chain or some signal is not reliable, the electronic control unit will set the record of 
malfunction information in the RAM of malfunction memory. The record of 
malfunction information is stored as diagnostic trouble code and displayed in the 
same order as the occurrence of the malfunctions. 

Based on their frequency of occurrence, the malfunctions can be classified as “steady 
state malfunction” and “random malfunction” (such as the malfunctions caused by 
temporary circuit open of wiring harness or defective contact of connectors). 

·MALFUNCTION STATUS 

If the duration period of the identified malfunction exceeds its setting stabilizing time 
at the first time, ECU will regard this malfunction as a stable malfunction and store it 
in the memory of “steady state malfunctions”. If the malfunction disappears within its 
setting stabilizing time, it will be stored as “random malfunction” or “non existence”. 
If this malfunction is identified again, it will still be regarded as “random 
malfunction”, but the “existence” of historic malfunction will not influence normal 
operation of the engine. 

·MALFUNCTION TYPES 

Short to positive grid of power supply; 

Short to ground; 

Circuit open (if there is pull up resistance or pull down resistance in input stage, the 
ECU will regard the malfunction of circuit open on input terminal as the malfunction 
that the input terminal is short to power supply or to ground.); 

Unreliable signals. 

·FOUR TYPES OF MALFUNCTIONS 

Maximum malfunction, the signal exceeds the upper limit of the rated range. 

Minimum malfunction, the signal exceeds the lower limit of the rated range. 

Signal malfunction, no signal. 

 

G-21

 

Illogical malfunction, there is signal but the signal is not logical. 

·LIMP DRIVE 

If some detected important malfunctions last longer than the setting stabilizing time, 
ECU will take proper software measures, for example, disable some control functions 
including the oxygen sensor closed loop control and the like, replace some unreliable 
data with the setting values and etc.. Therefore even the working condition of the 
engine is quite bad at that time, but the car still can be driven. The objective of such 
measures is to drive home or drive to service station limpingly so as to avoid the 
embarrassment that the car has to be broken down on highway or in field. As soon as 
the detected malfunction disappears, the normal data will be reused. 

·MALFUNCTION ALARM 

Some cars equipped with M7.9.7 system have the malfunction alarm light. If some 
important components such as ECU, the air intake manifold absolute pressure sensor, 
the throttle position sensor, the coolant temperature sensor, the knock sensor, the 
oxygen sensor, the phase angle sensor, the fuel injector, two drive stages of idle 
actuator with step motor, the carbon canister control valve, the cooling fan relay have 
malfunctions, when the corresponding malfunction flag bit is set, ECU will send 
alarm through the malfunction alarm light until this malfunction flag bit is reset. 

·MALFUNCTION READOUT 

The malfunction information record can be called from the electronic control unit 
through the diagnostic tester, or be read through the flashing code. If the malfunction 
is related to the function of fuel air mixing ratio regulator, the corresponding 
malfunction information record can be read at least 4 minutes after the engine starts 
running. 

 

ISO 9141-2 Standard diagnostic connector 

 

 

 

 

Connection to the diagnostic tester 

This system adopts the “K” line communication protocol, and utilizes the ISO 9141-2 
standard diagnostic connector (shown in the above figure). This standard diagnostic 
connector is fixed on the wiring harness of the engine. The 4#, 7#, and 16# pins of the 
standard connector are connected to the engine management system (EMS), the 4# 
pin is connected to the ground wire of the car, the 7# pin is connected to the 71# pin 
of ECU (i.e. the “K” line of engine data), the 16# pin is connected to the positive grid 
of the battery. 

 

G-22

 

The detailed procedures are:   

Turn on the ignition switch, but not start up the engine, ground the 7# pin of ECU by 
K wire for more than 2.5 seconds, then open the ground connection, after that the 
coding light starts flashing. 

After the K wire is grounded for more than 2.5 seconds the output of flashing code is 
the value of P-CODE. For example, the flashing method of P0203 is: consecutive 
flashes of 10 times-pause-consecutive flashes of 2 times-pause,-consecutive flashes of 
10 times-pause-consecutive flashes of 3 times. 

·CLEARING MALFUNCTION INFORMATION RECORD 

After the malfunction is fixed, the malfunction information record in the memory 
shall be cleared. Such malfunction information, which appeared at the time of ignition 
but failed to be maintained to the end of stabilizing period, will not be recorded. If the 
value Hz of frequency counter reaches 0, the malfunction information records in the 
malfunction memory will be cleared automatically. The malfunction information 
record will be cleared upon the demand of “clearing the malfunction memory” 
through the diagnostic tester. The malfunction information records in the external 
RAM can be cleared by disconnecting the connector of ECU or removing the wire of 
the battery. 

·TROUBLESHOOTING: 

WE ONLY CAN KNOW THE ROUGH POSITion of the malfunction whose 
malfunction information record is obtained through the above measures, and it doesn’t 
mean that we have found out that malfunction exactly. Because any malfunction is 
possibly caused by the damage of electric components (such as sensors, actuators or 
ECU and the like), the circuit open, or the circuit short to ground or positive stud of 
battery, even the mechanical malfunctions. 

The malfunction is intrinsic and its appearance is various symptoms. After the 
symptom is detected the diagnostic tester or the flashing code shall be used to search 
the malfunction information record, and excluding corresponding malfunction based 
on the malfunction information. And then carry out the troubleshooting based on the 
symptom of the engine. 

 

 
 
 
 
 
 
 
 
 

 

G-23