Electrical Nightmare.......
 

High guys......I have feed back in the power wire from the battery to the fuse box..I chased it down to the ignition switch plug wiring.

When I hook up a test light to the wiring going to the ignition switch, unhook the positive cable and touch the other end of the test light to the positive post....it lights up....does'nt this mean I have a short to a ground somewhere in the ignition wiring ???

When I unhook the ignition wiring from the back of the ignition key portion, this light goes out....no more feed back....or if I turn the key off....no more feed back..

WQe are having trouble with the car starting, it seems like the igniter is not getting the message from the ignition, and this is not all the time...it seemd like when a relay or something get hot it keeps the signal from reaching the igniter..?

So we started looking for a bad relay or something and found this wire with I think a "ground" feed back...

OK....so how's that for a mess.......We have unpluged items one at a time to see if the light will go out....so far no luck...do we keep trying this until the light goes out or what.....?????

What the hell are you asking??? Seems you don't know what you're talking about at all or have had WAY too much coffee and can't explain it well... or both... or it's just me (I'm no good with wiring, as anyone here... last person who should be giving any advice on it. ;) ).

A problem with the wiring up to the switch is going screw with a LOT more things than just the igniter... and much more directly. Have you checked for diagnostic codes? What other problems are you having? Have you tested the power at the ECU to make sure all the right terminals have the right amount of power at the right time?

what exactly is the car doing? i had a similar problem, but i am also rather confused... i think. :umno: So does it crank and not start? does it not crank or what?


When you turn the key to the on position, does the check engine light come on?

The car will crank but will not start, it will start up & run sometimes. We can go a couple of days with it running OK, then it will crank but not start..The check engine light comes on with the key on. I also am not able to get any codes from the TCCS.

We have replaced the coil, new plug wire, new plugs, new cap & Rotor, new igniter, main relay in fuse box under hood. We have not replaced the ECM or any other computer type items yet...

As I said oginally, I believe that we have a bad relay or something that when it will not start, I get a negitive feed back on what (I think) is supposed to be a positive feed wire. When I say negitive feed back I mean that when I unhook the positive cable at the battery, touch a 12 volt test light to the positive post, then touch the 12 v test light clip end to the power wire to the fuse box, it lights up.

I am in the process of unhooking/unplugging things to see if I can get the 12v test light to go out, so far no luck...

I have traced the wire in question back to the ignition switch. When I turn the key off or unplug the harness, the light goes out....

- Could the "Circuit Opening Relay" or the "Fuel Pump Relay" give me a negitive reading (like it was grounded) if one of them was bad ??

- Since the wire in question seems to be associated with the ignition switch system, would that mean that the failure would be confined to the engine electrical more so than the cab or chassis wiring ??

I am trying to be as detailed as possible so you know what we have done and what we are trying....I have all the wiring diagrams from everyone.

Thanks

for CRE - The....white....wire....is.....sending....a.....ne gitive.....reading.......the.....
car....will.....crank......but......not......start ....sometimes......just kidding...:bow:
Thanks for the help....

Hey you dont have a ground goin to that wire so look elsewhere, what you are doing when you hook the test light in line with the positive on batt to the wire that is also positive you are creating a circuit showing power going through that whole circuit. do this exper. unhook positive cable from batt. the put the lil clamp dilly on it and then touch the probe to the pos. post on the batt... Wallah the light will light up because you have created a circuit. the light can light up because any dc power ultimatly runs to a ground so even hooking inline will cause your light to light up...First thing to do is throw that test light in the trunk where you keep spare fuses thats all its good for, and get a digital multimeter. they can be had for 20 bucks at wally world. the go ground on your black wire and go to the wire with red.... it should read about 12.5 atleast, or whats at your batt.. if it reads 12.5 at batt and 11 at wire then you have a high resistance some where could be caused from the ground bein corroded (most likely) or a bad connection on the positive side of things but grounds tend to corrode first!! i was a certified RV Tech. and we did ALOT of electrical troubleshooting. but i have now moved on to airplane elctrical systems.... hope this helps....

And they called him "codebreaker" ever since.... lol.

Thanks Travis89turbo....who were you with CW or should I say Blaine Jensen RV ?

See ya,

No i actually worked for Sierra RV. its further north then blaine jensen but i do kno them and there business. Sierra WAS the largest private owned and operated dealership in UT with over 28 million in inventory. until Genral RV moved in a week ago....!!!

My thoughts exactly, multimeter ftw. Test lights are fine on old-tech but for anything like the Supra with ECU controlled circuits a multimeter is a must, can do a lot of damage with a test lamp & an ECU!!! Oh & plug everything back in now too, if it runs sometimes then whatever is causing the fault can't really be a short or you'd be blowing fuses, flattening batteries overnight or starting fires...

tbh the intermittent bit does sound like possibly a relay or bad connection, do you have a spark when it's cranking but no-go? this will at least tell you which side to be looking for the fault rather than trying to trace back from the ign. switch loom.

electrical problem
 

I had the same problem with one of my mk3's. It took multiple mechanics to find the problem and it turns out that the main relay was replaced with one with a different circuit. Good buy a new one and check that first they are like 18$ from Toyota.