Originally Posted by C. Ludwig

I’ve spent a lot of time on the phone with Lance over the years. Give him a call. He loves to talk. Plan your day accordingly.

The coils are designed for an OE application that utilizes misfire detection. The multiple grounds are part of that feature. Since none of us in the aftermarket are making use of it, the two low level grounds, pins B and C, should not be connected to ECU reference ground. They should be connected to the head or rotor housing. Connection of pin B to ECU reference ground could, in the event of coil failure, allow the coil to pull high current ground through the ECU causing ECU damage. This is the primary reason to not connect pin B to ECU reference ground. Combine that with the fact that the function that the coil reference ground serves to non existent in the aftermarket and there is not a good reason to connect pin B to ECU reference ground. The OP’s coil melt down wasn’t caused by pin B not being connected to ECU reference ground and won’t be solved by doing so. Claudio, myself, and many highly experienced builders don’t use ECU reference ground for these coils. The only place many of us differ is whether we take pin D to the head/rotor housing or the battery.

I’ve said it for years, decades now, AEM doesn’t know anything about the coil they rebranded. The diagram they use is from Lance and depicts the OE configuration.

The coil harness connector should be weather tight but it’s also 30+ years old and has lived a hard life in one of the harshest engine bays ever created. Water ingress isn’t surprising. New connectors are available. Dielectric grease also goes a long way to keeping water out.

Without being hands on, we’re all guessing at the cause of the failure. I’d start with checking to make sure the ECU is properly configured for the coil configuration and toning out the harnesses to make sure there are no shorts and the configuration is correct to suit the coil configuration. If you need help, feel free to contact me directly.