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Car body used as common earth?

EFI Wiring Fundamentals

Discussion and questions related to the course EFI Wiring Fundamentals

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I thought the car body was used as a common earth? In the demonstration it is said the engine is the common earth so you can't get a common ground. In a regular car the body is the common earth, so wouldn't this allow common grounds?

While the battery will be earthed to the chassis, we use the engine block for the common star earthing point for all the ECU grounds. The Engine block will also have a ground strap to the chassis so in reality the chassis and engine block should be at the same ground potential but using the engine block as the common earth point for our ECU means we've got less chance of issues creeping in if a ground wire fails in our ECU wiring.