Does power travel directly to the ECU from the underhood fuse box? Or does it go from the under hood fuse box to the Main Relay, then to the ECU?

If anyone can read schematics, Ill post a pic below. I dont think my P28 ECU is getting power. I noticed this because my boost controller is not powering on. The boost controller is set up on ignition power source pin A25 (YEL/BLK) but when I turn on the key, it does not power on. It should turn on when the key is turned to ACC without starting the car. I used a multimeter and checked the connector at the ECU, and it doesnt look like any current is getting to the plug. ECU main power comes from the under hood fuse box (15A fuse) which is not blown, but Im not sure if its routed through the main relay before reaching the ECU. I used the multimeter and was able to verify power is reaching the fuse connection. So it looks like Im losing power somewhere between the fuse, and ECU. I dont see a YEL/BLK wire coming out the bottom of the fuse box, so Im assuming its routed to the main relay where the wire becomes YEL/BLK.

I havent tried to start the car yet because Im trying to verify wiring first and the car has no fluids installed anyway. And by the way its my ITR motor so it is ITR related




Modified by RTW DC2R at 12:25 AM 4/14/2008

 

ry if you post a wiring diagram i can help you....but off the top of my head i wanna say its relayed

 

there is a fuse for the ECU too under the hood and i wanna say its a 15a

 

yeah there is a 15A fuse underhood (i already stated that ) but I dont know where power goes after that. im pretty sure its relayed too but not positive and not sure what color wire it would be coming into the main relay. i have a pic of the schematic but we-todd isnt loading

edit... pics up


Modified by RTW DC2R at 12:26 AM 4/14/2008

 

It starts as YEL/WHT at the fuse box and then goes to the relay and from the relay it comes out as YEL/BLK and then feeds the YEL/BLK at the ECU. The wires are only connected where a dot is. If they cross over each other and there is no dot, that means they are not connected.

 

yea i suck at reading

is there power at the main relay? the yellow/white wire?

 

ok so power from the fuse box comes out as YEL/WHT? so Ill check for power at the YEL/WHT terminal on the main relay tomorrow after I get everything plugged back in. heres a pic of the main relay, let me know if you think its shot. I didnt check for power going into the main relay because I already had it out of the car before I checked back to the post. I might also try to swap in my ITR relay tomorrow as Im pretty sure they are interchangeable with my 92 hatch.




Modified by RTW DC2R at 1:12 AM 4/14/2008

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RTW DC2R &raquo;</TD></TR><TR><TD CLASS="quote">ok so power from the fuse box comes out as YEL/WHT? so Ill check for power at the YEL/WHT terminal tomorrow after I get everything plugged back in. heres a pic of the main relay, let me know if you think its shot. I didnt check for power going into the main relay because I already had it out of the car before I checked back to the post.

</TD></TR></TABLE>

Yeah from your schematic it comes out of the fuse box as YEL/WHT. The relay consist of diodes and inductors so if something went bad you would smell it because when diodes go bad they will burn up and smoke. The inductors would have to be tested so you would actually have to take it apart to see if they are working. The bottom of the relay looks fine, that brown crap is just solder rosin and the solder joints look fine.


Modified by Spids5 at 10:23 PM 4/13/2008

 

thanks for the info! we'll see how it turns out tomorrow, off to bed.

 

also a quick note, I checked the main relay plug to see if there was any obvious damage to the YEL/BLK wire, and noticed there are actually two YEL/BLK wires on the terminal exiting the relay. and after looking at the schematic, it looks like the other YEL/BLK wire goes to pin B1 Power Ground. could I use that wire as well in case there is a problem somewhere along the A25 wire after the main relay?


Modified by RTW DC2R at 9:48 AM 4/14/2008

 

Yeah B1 and A25 are fed from the same source so you could tap into one if a wire is broken somewhere along the way.

 

a tech question ? no one is left that knows anything like that , didn't you hear ?