leds, ems car shuts off

This is my first post here. I am having a problem that doesn't make sense to me and I don't know how to narrow down. Here's a breakdown of what I have (since any of this could be affecting the issue.)

I have a 2005 Scion XB. I've added an AEM F/IC (Fuel/Injector Controller for the turbo) piggyback Engine Management System that connects to the stock ECU via a plug-n-play harness.

I've installed a Pioneer Avic-z1 with sirius, ipod, bluetooth, etc. etc. (they were all working when I started this project, but now the headunit doesn't respond. I can trace this, but thought I'd mention it.)

I added Autometer Nexxus gauges to the system and a Autometer tach that connects to the tach signal wire coming off the back of the OBD2 port.

I added a Tein EDFC controller.

I added a secondary oil pump that just has a +/-.

I installed LEDs in the interior, engine bay, and underbody.

I installed an Auterra DashDyno SPD that just connects to the OBD2 port. (Just like a ScanGauge)

The ACC wires of the gauges, shift light, and stereo hook into the fuse panel using add-a-fuse to a known(tested with multimeter) open ACC port.

The oil pump is in an add-a-fuse tap to a known(tested) open "Ign. ON" port.

The power (12v) for the gauges, shift light,  and EDFC run to a 10 AMP fuse at the battery + (this fuse is shared... more on that next)

There are four total wires coming off the side battery + post that share the 10 AMP fuse. One of these goes to the above mentioned. The other three individually go to 20 AMP switches for LEDs.

The LEDs are wired as such:

Switch 2 : 22 ga wire to fused power distribution block. 5 AMP fuses for each accessory. Slot 1 = LED strips in grab handles, Slot 2 = LED strips in engine bay.

Switch 3 : 22 ga wire to underbody controller.

All of these items (except the radio and F/IC since they use harnesses) are grounded to a ground distribution block hooked to a factory chassis ground under the dash.

Everything was working wonderfully for about a week. Last night I tried switch 3 and it worked. I tried switch 2 and got nothing. Checked the fuses and they were good. Here's where it gets WEIRD and my main reason for the post:

With the car at idle, if I flip switch 1 for the interior LEDs, the car stalls!?!?

So here's a crude layout of how this is wired.

Any help at all is appreciated. Thanks!

You have what we call an electrical nightmare.   :)

I would start by ignoring switch 2 - even unhook it at the actual switch.

Then, check to see if switch 1 still stalls the car.  If it doesn't stall focus on switch 2.

If it does stall remove one fuse from the distribution box on switch one and throw the switch again and see if the car stalls.  If it doesn't, you've identified the circuit that needs to be inspected.  If the car doesn't stall pull another fuse and repeat until all three fuses are pulled out.  If all three fuses are pulled out and the car still stalls you can inspect the wiring between the fuse block and the switch.

Do you have any indication as to why the car is stalling (no air, no fuel, no spark, etc)?  Have you tried bypassing the AEM and seeing if that changes anything?  I wouldn't think it would, since it is plug and play, but it may be worth trying.  At idle you shouldn't have any issues with running lean and damaging the motor, just don't boost the car with it bypassed.  I would also unplug anything from the OBDII port and seeing if that "fixes" anything.  The more things you can disconnect and isolate the easier it will be to discover the true problem.   

Sorry I did not answer your question. I dont think it sounds like anything to do with the lights does the service

light come on before it stalls or after?

Thanks for all of the suggestions! I followed Kevin's advice and tried to isolate the issue. After stepping through the current flow with my multimeter at different locations I found that my continuity was horrible on one of the wires feeding accessories on switch 2. I pulled it completely out and replaced it with a new wire and switch two worked again. I looked over the wire and found a "crimped" section with a tiny split in the insulation where it crossed the main feed of switch 1. I had wrapped every wire I ran in electrical tape (I always do this the full length of the wire to help it keep that OEM look.) except these wires for the switches. They are now wrapped. :) I tried them running without any drop in voltage and no noticeable difference in idling performance.

I'm taking a shot that it was causing some type of ground loop fault scenario and since the EMS relies on voltage from sensors to adjust injector cycle and timing it could have theoretically seen incorrect values when I sent power to that first switch.

A couple of good points I'd like to make in case anyone else searches this topic.

As far as resetting the ECU, you should reset it anytime you add any performance part. (ie: intake, header, exhaust, pulley, turbo, s/c, etc.) I know that's a wide range and seems a little rediculous, but most newer cars have faster/larger processors in them. Rare are the days of finding 8 bit ECUs. They almost all are "Learning ECU's" that adjust different aspects of the vehicle based on your driving habits. It thinks it can make itself run wonderfully and save you some money on gas. For the most part it can. But, if you go changing anything on the car, give your ECU a break and let it start the learning process over. It will make a difference in the long run.

Anyways, now that I've got that out... thanks again for the quick responses and helping me stay on track guys!

Come on people I am quite aware that you can plug laptops and scan tools into OBDll ports you can also

change the pramaters of the motor to get more preformance, But if you dont know what your doing its not a

good idea to attach anything to this plug. And I am not sayin' this person does not know what he is doing!!

I have seen it before all it takes is a kid watchin' the next import racin' movie a laptop and a program

and they think there a speedracer until they try to start there car then there parients call the shop to see when

we can get it in.

I don't see a problem with that scenario.  Kid watches TV, does something he sees as an example, and you get another customer. 

BTW, the next person who blames TV, Movies, Music, or Video Games for the stupidity of thier children are gonna get the royal smackdown.

OBDII connections can and will work.  If you know what you are doing, there's no harm in tapping into the OBDII.  It's not unlike anything else in a vehicle or anywhere else for that matter, if you don't know what you are connecting into you're gonna mess something up.

He said he put a shift light on the tach wire at the OBDII port and a "scan guage".  Where did he ever say he connected anything that could change any parameters of the ECU?  With what he connected there is virtually no risk of harm to the vehicle.

Just a quick question about your "shot" as to why things weren't working - weren't you switching the + of the wire through the switch?  If so, how could that cause a ground loop?  And, also weren't you using a power wire directly from the battery?  If so, the signal paths for all the engine sensors should be on seperate fuses/circuits and you shouldn't have been able to harm them.  I think there was something more going on, but since you got it fixed that is all that matters!