I finally got around to building my circuit that disables Stop/Start upon startup. It seems to work! - in the garage - I've yet to try it on the road.
Here's a video of it lighting the disable light 5 seconds after startup. The button is still usable to reactivate the Stop/Start if desired. No DTCs are displayed (just low gas).
Here are some details for the techie folks...
I've included a picture of the circuit diagram and the circuit itself.
The circuit is basically one of these connected to a SPST relay which connects to both pin 8 and pin 10 of the headlamp switch module through separate resistors. When the relay is active, it connects the pins to ground through their respective resistor.
Each pin has a separate non-pressed and pressed resistance. I guess this is to help the Body Control Module detect open connections or shorts. The values of the resistors used in this circuit are calculated to match the normal button press value when run in parallel with the non-button press value.
The timer has to be programmed through a procedure to make the appropriate pulse after 5 seconds. I used timer function 7 with a t1 of 6 seconds and t2 of 1 second. Once programmed, it retains the function indefinitely.
I used these which match the diameter of the wiring harness wires. They allow easy removal of the circuit if needed. This is the I used. This has the two values needed - 1900ohms (I used 2K) and 675 ohms.
Installing it is a little tricky. The headlamp switch module prys out. There are four spring loaded clips in the upper right, upper left, lower right and lower left. You have to gently alternate prying on these four spots little by little. Don't pull on the chrome ring around the knob - it comes off easily. This reveals the connector which can be unplugged to install the t-connectors to the appropriate wires. The diagram is from the perspective of looking at the connector from the back side where the wires come out. I pushed the relay and timer through the opening in the dash frame zip-tied it to keep it from rattling.
If anybody else wants to try this I'd be happy to answer questions. It does require some soldering skills and some basic electronics knowledge would be helpful. Testing on the bench should be done before install.
Here's a video of it lighting the disable light 5 seconds after startup. The button is still usable to reactivate the Stop/Start if desired. No DTCs are displayed (just low gas).
Here are some details for the techie folks...
I've included a picture of the circuit diagram and the circuit itself.
The circuit is basically one of these connected to a SPST relay which connects to both pin 8 and pin 10 of the headlamp switch module through separate resistors. When the relay is active, it connects the pins to ground through their respective resistor.
Each pin has a separate non-pressed and pressed resistance. I guess this is to help the Body Control Module detect open connections or shorts. The values of the resistors used in this circuit are calculated to match the normal button press value when run in parallel with the non-button press value.
The timer has to be programmed through a procedure to make the appropriate pulse after 5 seconds. I used timer function 7 with a t1 of 6 seconds and t2 of 1 second. Once programmed, it retains the function indefinitely.
I used these which match the diameter of the wiring harness wires. They allow easy removal of the circuit if needed. This is the I used. This has the two values needed - 1900ohms (I used 2K) and 675 ohms.
Installing it is a little tricky. The headlamp switch module prys out. There are four spring loaded clips in the upper right, upper left, lower right and lower left. You have to gently alternate prying on these four spots little by little. Don't pull on the chrome ring around the knob - it comes off easily. This reveals the connector which can be unplugged to install the t-connectors to the appropriate wires. The diagram is from the perspective of looking at the connector from the back side where the wires come out. I pushed the relay and timer through the opening in the dash frame zip-tied it to keep it from rattling.
If anybody else wants to try this I'd be happy to answer questions. It does require some soldering skills and some basic electronics knowledge would be helpful. Testing on the bench should be done before install.