Can't remove the fault code using the method of demolition of battery cables for most electronic control engine, remove the battery cable or remove the fuse to the ECU, remain without electricity for 30 seconds, can eliminate stored in the ECU fault code.
But for some of the engine, it is not suitable for this method, because the vehicle anti-theft, acoustics, quartz clock, etc are stored in ram memory, the memory will also be removed together when the power is cut off, leading to the stereo lock code wait for a phenomenon, of the engine should be in accordance with the requirements of maintenance manual methods to remove the fault code, should not be arbitrarily demolition of battery cables.
Not to read fault codes of electronic engine control unit records before can't dismantle battery cables because before the fault code reading and to remove the battery cable or unplug the power fuses, due to the power supply interruption of ECU, the fault code stored in the ram will be automatically eliminated.
To get fault information must be duplicate or reproduce the work state of failure and environmental conditions, and for the engine won't start, so after operation can no longer get the fault code, lost an important fault diagnosis information, therefore, before the electronic-controlled engine maintenance, should be required to record ECU fault code first, then perform other maintenance.
When the ignition switch is in the on position, can't literally dismantle battery cables when the ignition switch is in position, whether or not the engine running, can not remove the battery cable or unplug the power fuse.
Because of sudden power outages can make coil in a circuit to produce self-induced electromotive force, resulting in a high transient voltage, the ECU and related sensors such as microelectronic devices severely damaged.
In addition, all the same as the battery voltage of the other electrical device wire, also cannot be pulled down when the ignition switch ON, otherwise the same coil related causes self induction electromotive force, thus the ECU or sensors.
These electrical devices including: ignition system, idle speed stepper motor and ECU programmable read only memory (ROM), fuel injector, air conditioning and other electromagnetic clutch, and ECU some cables, etc.