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A VW Lavida found the warning light flash on the dashboard after replacing battery.Technicians checked the wire harness,it works normally.And according to the repair experience,it was believed that ELV get error.
Remove the ELV PCB,detectd it by multimeter:
There is a audion damaged on the PCB.
And technicians the interior power supplier work incorrectly.There is a L4949ED chip damaged.L4949 chip is a low voltage power supply module.
After replacing the new electronic components,the trouble was sloved.This trouble is caused by replacement of battery.
Why after replacing battery and power on again will result in the trouoble.
The reason is that the automotive electronic equipment has high requirements on the stability of the power supply,especially some European and American cars.If you understand the electronic technology:the CPU is supplied by 5V power and the other automotive electronic parts is supplied by 12V power.The 5-voltage power is step-down to 5V,then supply to the CPU.
However,once the 12-voltage power fluctuates greatly,for examply,during the moment of car starting,motor need largee current,it will make the 12-voltage step down.At this moment,if the battery does not have enough power,it will make influence on the 5 voltage when you start the engine.
This unstable power supply will result in data damaged on CPU or EEPROM,we call it data lost.After data losing,the relevant electronic equipment will work incorrectly.And if you connect the battery in wrong method,battery ternials poor contact and generate spark,it make automotive electronic equipment damaged.
How to avoid the trouble?
If you find the battery lack power when you start your car,you have to stop to charge the battery.
For example,if your car has parked in your garage for a month,you would better to recharge the battery,the try to start the engine.
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