Fault Code 1117

[Rawze]

(08-25-2020 )DVT873 Wrote:  I need to think about this a bit more. Forgot about the kick back. Thanks

Yeah, when a magnetic field collapses, it creates a kickp-0back current and voltage. If it has nowhere to go, that voltage will climb into the tens of thousands of volts or more range until it finds and jumps across a pathway. Usually the relay or electronic circuit that is attached to ... hence the spark seen as the contacts open on a relay (wears out the relay eventually) .. or jumping the silicone substrate inside a solid state device like a transistor, Diode, FET, or SSR whatever is controlling it. The Only way to stop it is a diode in reverse across the power to ground so that the voltage can be safely bled off.

The 2 diode approach you used would be fine as long as that kick-back has somewhere to go (a 3rd diode in reverse from power to ground of the coil itself). ... or just using a single diode to protect the ecm, a second one in reverse across the coil to bleed kick-back off, and a small fuse to protect the ignition circuit (needed regardless of what approach you take) in case anything in the circuit fails.