Supplies the whole vehicle before the alternator takes over, and stabilises voltage afterwards. Its most important property for diagnosis is indirect: modules and actuators do not simply stop when voltage sags, they misbehave — solenoids move slowly, sensor references drift, network messages corrupt, modules reset mid-operation. A failing battery or a corroded terminal therefore produces a page of unrelated faults across transmission, ABS and engine systems, none of which are real. Test the battery before diagnosing any of them.
Also known as: car battery, starter battery, accumulator, 12v battery
Referenced by 218 codes
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
A car battery does one demanding job — deliver several hundred amps for a few seconds — and one undemanding one, holding the memory circuits alive while the car sleeps. It is very...
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