The engine electrical systems include all ignition system, charging, and starting, that is different to chassis electrical devices such as lights and instruments. Cautions should also be taken when dealing with the electrical system, engine electrical parts are easily spoilt when handled carelessly. Extended periods of keeping the ignition on when the engine is off are not to be allowed and
Battery Cables should never be disconnected when the engine is on. Most importantly, in servicing the electrical system, always disconnect the negative battery cable and always isolate the cable to avoid coming in contact with the battery terminal. Certain car systems need continuous battery operation to keep the vehicle functional or in memory, therefore, one should switch the ignition and lighting switch off before disconnection of battery. It is possible that once the battery is reconnected the Transaxle Control Module might require time to relearn its adaptive strategy and the Powertrain Control Module will also require time to relearn its idle and fuel trim strategy. In some models, it might be required to calibrate the cluster display and initialise the power window system. There are memory savers that can be used to save the security codes and PCM memory when the battery is disconnected. After battery replacement, there are special steps to follow to guarantee the idleness and functionality of Batteries Monitoring System on the newer models.