Just a quick question I hope. I was wiring up a 5 pin relay to have on toggle switch from IAT sensor to 2.2ohm resistor. On accident I touched 12v positive from battery to IAT wire, so basically I sent 12 v to ECM from one of sensor wires. ( i cut blue one in half and piggybacked to black) I haven't started truck yet and it's getting really cold out too I might wait till end of week to start. But with key on and switch off I get 143f on IAT gauge and if I flip switch on I get ambient temp of intake. I figured ill wire it up this way so the relay is not energized when I'm fooling IAT, most of time it will be fooled anyway so I'll use relay to switch to IAT only for warm up and then shut off switch and be on resistor with relay dead. I guess I have 2 questions could I fry ECM by sending juice back to it through IAT wire and any side effects with the way I wired up relay. Thank you all for your help.

If you are still reading the proper readings you are very lucky !!!!

Ed

As a matter of fact I did that once by accident doing electrical work when I was very tired. I sent full battery power thru the ECM ground. After which I disconnected batteries for about an hour. I can't remember but my temperature gauge or the volt meter was pegged after that. after letting it sit for an hour with batteries disconnected it went back to normal.

Edited January 5, 201510 yr by JAG1

If you are still reading the proper readings you are very lucky !!!!

Ed

Would it only affect IAT or the whole ECM? With the mistake I made, as of now without starting I can toggle between IAT and resistor and it's working, just curios if other thing could get messed up. And would it really matter which way you make relay work normally closed or open? Though about buying yours and Mikes high idle/mpg/3cyl but no need for 3cyl and have high idle with my qwad so just wanting IAT fool. Thanks.

Edited January 5, 201510 yr by Dieselfuture

Would it only affect IAT or the whole ECM? With the mistake I made, as of now without starting I can toggle between IAT and resistor and it's working, just curios if other thing could get messed up. And relay would it meter which way you make normally closed or open?

Edited January 5, 201510 yr by Dieselfuture

You can screw other things up for sure.  One reason disconnecting your batteries are a good practice.   One that I don't follow as well as I should.

Ok just drove it today, everything seems to work. Guy got get lucky once in a while.