Chery automobile Service Manual page 332

Repair Details of Random Failure:
In the electronic control system, the instantaneous and poor contact problem may occur in such
positions as the electrical circuit and input/output signal passage. Thus it causes the random failure
or generates the DTC when ECU self-checking. If the reason of failure still exists, the abnormal
parts can be found only in accordance with the DTC Failure Check Sheet, but sometimes the reason
to cause the failure will disappear automatically, so it is difficult to find out the reason of problem.
In this case, simulate the failure and check whether it reoccurs in accordance with the following
methods.
When the major reason may be vibration:
* Slightly swing the connection up and down;
* Slightly swing the harness up and down, left and right;
* Slightly swing the sensor up and down, left and right;
* Slightly swing the other motion parts such as wheel bearing.
Caution: If the harness is twisted off or pulled tightly and then broken, it is necessary to
replace it with a new one, especially it may cause the transient open/short circuit of
sensor due to the up and down movement of suspension system when the vehicle is
traveling. Thus the actual vehicle test must be conducted when checking the signals
from the sensor.
When the major reason may be over hot or super-cold:
* Use a blower to heat the parts that you think it may be failed.
* Use the cold spraying agent to check the cold welding phenomenon.
When the major reason may be the over-high contact resistance in the power supply circuit.
* Turn on all electrical switches, including the headlamp and rear defroster switches.
If the failure doesn't reoccur here, it may be diagnosed and repaired only when the failure occurs at
next time. The random failure will generally become worse only, and is difficult to get better.
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