ASD kill switch

[Jerry Bransford]

I don't see where it says that anywhere.

It says that in earlier model FSMs like for my 97, as quoted below.

But it appears we are both right depending on the model year. My '97 TJ's ASD relay directly controls the fuel pump relay, I knew that's how my '97 worked when I entered into this conversation.

'97 FSM page 14-26

AUTO SHUTDOWN (ASD) RELAY-PCM OUTPUT
The ASD relay is located in the Power Distribution
Center (PDC) (Fig. 2).
The ASD relay supplies battery voltage to the fuel
pump, fuel injector, ignition coil and both oxygen
(02S) sensor heating elements. The ground circuit for
the coil in the ASD relay is controlled by the Powertrain
Control Module (PCM). The PCM operates the
ASD relay by switching the ground circuit on and off.

How the above works changed in later years. The below is out of the 2005 FSM...

OPERATION
The Powertrain Control Module (PCM) energizes
the electric fuel pump through the fuel pump relay.
The fuel pump relay is energized by first applying
battery voltage to it when the ignition key is turned
ON, and then applying a ground signal to the relay
from the PCM.
Whenever the ignition key is turned ON, the electric
fuel pump will operate. But, the PCM will shutdown
the ground circuit to the fuel pump relay in
approximately 1–3 seconds unless the engine is operating
or the starter motor is engaged.

The later years including the 2005 uses the ASD relay as one means to tell the PCM when the engine has stopped running. When that happens the PCM will then remove the enabling ground signal to the fuel pump relay shutting it off.

 

[LONGJP2]

The later years including the 2005 uses the ASD relay as one means to tell the PCM when the engine has stopped running. When that happens the PCM will then remove the enabling ground signal to the fuel pump relay shutting it off.

I've read the 2006 (and 2005) FSM many times and it says nothing about the PCM using the ASD sense signal to control the fuel pump. Not saying the PCM doesn't turn off the fuel pump, but it doesn't appear to use (or care) about the ASD to determine if the engine is running or not.
I might get the meter out and experiment a little with the relays, but I think I'll leave my kill switch as is.

 

[jrundquist6]

The wiring colors have apparently changed in the ASD wiring circuit for your 2005. The below schematic is from the 2005 Mopar FSM.

What I would do is cut the brown wire with white tracer where I placed the red X and insert a good high quality SPST on-off switch into that wire. This is the same modification I suggested above but with the updated wiring colors for your 2005. This is a critical circuit so take your time.

View attachment 220366

I feel like over designing a kill switch by putting in a microcontroller to interrupt the line you've put an x through using a relay. I've found a nifty latching relay that'll stay put even when it loses power. Any way, I'm wondering if anyone know the voltage or amperage running through this wire? 12V, I'm okay with, and a 20AWG wire so likely less than 3 amps, but has anyone put a multimeter to this to really see?