Kill switch for my 2008 VW

[theholycow]

The good news:

• It kills the engine, as I expected.
• It does not throw a code.
• It keeps the gauges and ScanGauge live, as I hoped. No more guessing when the engine dies, I can see it on the tach (and I can hold the button longer if necessary anyway).
• Bonus: When I kill the engine that way, I only get a battery light on the dash. Normally, done with the key, I get 3 lights.

The bad news:

• As I feared, I mounted the button too high and the boot bumps it sometimes.
• As I feared, it failed on the test drive and I couldn't restart. I had to pull over and undo it roadside. Luckily I made it very easy to mess with, by giving it spade connectors to plug into the fuse slot instead of splicing it in or re-pinning.

I attached it to the shifter using hot-melt glue, so it will be easy to remove and re-mount. That will take care of the shift boot issue. As for the other issue, that will require some troubleshooting...

[theholycow]

With nice weather today, I went outside and worked on it more. I moved the switch and now it's a little too low for comfort but it won't get tripped by the boot.

I put everything back in place and tested again, and learned:
- It didn't fail last time; the engine just won't restart after using the kill switch and EOCing a while without turning the key off and back on in-between. A quick EOC is no problem.
- It doesn't seem to force DFCO. If I push it while in gear, it seems to have no effect.

Any idea what 20amp fuse I found that would behave like that? The manual is entirely wrong about the fuse layout.

[theholycow]

So, I think my kill switch may be to blame for a CEL. I've got a P0420 which made me wonder if my car was asking for narcotics, but I looked it up and it means a catalyst problem.

According to http://www.golfmkv.com/forums/showpo...3&postcount=65 (a thread about a guy who blew his engine) :

01056 P0420 002
CATALYST SYSTEM, BANK1 EFFICIENCY BELOW THRESHOLD

well this means your 2nd oxygen sensor thinks your catalytic converter isn't up to federal emissions standards. In other words you sent a good chunk of unspent gas through your exhaust when you over revved, doubt your cat is actually bad.

So, I wonder if the fuse I used operates the ignition system and cuts it off somewhere that it's not monitored, causing the computer to continue sending fuel through the engine.

I should just interrupt the fuel injectors' common ground rather than trying to interrupt a fuse. How sensitive are fuel injectors? How clean is current flow through a common relay? If the relay has any resistance, is it going to have an effect when I'm not opening the relay with the kill switch?