Chery automobile Service Manual page 131

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