How to wire external shift light to check engine light?

TopMountGSR · Post by **TopMountGSR** » Fri Aug 28, 2009 7:34 am

Ok I have been wanting to add a external shift light but control it with ectune's ability to control the check engine light. I went to check the voltage at the check engine light and have been getting weird results. Like it has 12v when you cut the key on, then it has 0.89v when the check engine light is on, then goes back to 12v when the engine light turns off. This makes no sense to me, the other bulbs traces have 12v when the bulbs are on, ex oil light. Any help on this? I'm just wanting to activate another 12v bulb or a series of led's with a resistor. I don't mind running a relay if needed. Does anyone know the pin out for the check engine light? Thanks a bunch guys, I'm trying to goto the track today at 5pm and desperately need it when it gets dark because my dash ilum. lights crapped out and I found no blown fuses. dk

TopMountGSR · Post by **TopMountGSR** » Fri Aug 28, 2009 7:51 am

a13 mil, Its doing the same thing as the trace, its dropping voltage when the light comes on. I'm researching how to control a relay cutting voltage.

xenocron · Post by **xenocron** » Fri Aug 28, 2009 8:20 am

The CEL light has constant power to one side, the ECU pulls to ground. If you use a set of LED lights that dont draw much current, you can just tap into the CEL light circuit on the ground side. Give the LED array a constant 12v or use the constant 12 from the CEL light as well if you like. If you are using a Bulb or something that might draw more current than the ECU can handle, you probably want to setup a relay, although this will delay how quickly you see the light. Use LEDs if you ask me...

TopMountGSR · Post by **TopMountGSR** » Fri Aug 28, 2009 11:21 am

Thanks for your reply, I follow most of your reply, I have a ton to learn when it comes to schematics, circuitry, and my cars electrical system but I figured it out. What weird, I tested the voltage on both traces to the bulb and got a positive voltage when the check engine light was on, then I moved my ground, re checked and it was backwards again like I stated in my 2nd post. So I found the power and ground the clusters cel was using in the clusters plug, and hooked them up to some led's, works great, now I just need higher quality leds. Thank you for your time, this will really help me at the track.

TopMountGSR · Post by **TopMountGSR** » Fri Aug 28, 2009 1:27 pm

Any clue as to what my limitations is on how many, or how powerful led's I can use? What happens if I use to many? Does it burn up the output on the ecu?

greasemonkee · Post by **greasemonkee** » Fri Aug 28, 2009 5:12 pm

I've been running at least 240 mA on nearly every available output on multiple ecu's for well over a year. No failures to date - would take a handful of LEDs' to equal that.

TopMountGSR · Post by **TopMountGSR** » Sat Aug 29, 2009 1:15 am

Ah, thank you very much. This thing worked great tonight at the track! Can't I find a variable voltage tach signal output and some how put banks of leds that come on like a progressive multi colored shift light? Like indy cars and digital dash's Couldn't I set a few up to work off say 3v, then a few more at 4v and so on. I could figure out what resistors to use in led calculator. Wouldn't this work?

xenocron · Post by **xenocron** » Sat Aug 29, 2009 7:08 pm

EXTREMELY helpful website: http://www.the12volt.com/

TopMountGSR · Post by **TopMountGSR** » Sun Aug 30, 2009 3:42 am

Thanks a bunch Chris, I have seen some good info linked to that site, just never been to the home page. Excellent resource buddy!