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Discussion Starter · #1 ·
Thought I’d document this for others as the info out there is sparse.

You can use the stock Boost Control Solenoid for WMI failsafe activation and it’s actually fairly easy, the process is as follows:

Locate the BCS on the lower side of the engine block (cam chain end), it will have 2 wires, one a switched 12v live, the other a signal. With a multimeter you can easily check which is live when powering on ignition.

The signal wire is cut and wired through a 30a 5 pin relay on the Normally Closed pins (30 and 87a), when the relay is not active this retains control of the circuit by the ecu. It also doesn’t matter which of the 2 ends of the cut circuit wires are connected to which pins (30 and 87a) since it’s a NC circuit.

The AEM green failsafe is wired to the relay earth pin 85, this is especially important if the relay has diode protection.

Provide a 12v power source to the relay, can come straight from battery but I tapped into the BCS 12 switched live, works just fine. If connecting straight to battery power draw will not occur unless a lowside\earth trigger is activated.

If the aem controller triggers a ground signal, the relay then activates\switches and this disconnects the NC circuit and activates the NO circuit, which of course has nothing connected to it, your BCS now relies solely on WG spring pressure (14 psi on mine).
Most WMI meth systems that have a failsafe support a low side switch (ground signal) including Aquamist, Snow Perf, AEM)

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