No power to B+

[SupraSean]

I just got my engine back in and hooked up, and my mapecu wasnt coming on, so i thought i just may have wired it wrong. Come to find that the B+ Wire has No Current, Checked basic fuses, and the fusible link. Now there is one thing i'm unsure of, Is that wire, power FROM the ecu, Or TO the ecu. I know that it already has the yellow/black wire(BATT) Power. Checked Connections, i just cant seem to find the cause. I want to test continuity at the checkbox, but my dog found his way to chew my multimeter. Car is a 92. Thanks in Advance -Sean-

 

[3p141592654]

The ECU controls the B+ power line through the main relay using the MREL signal. B+ is the main power bus of the ECU, and applying 12V to the IGSW line will normally energize the main relay. Since it is not working, check for 12 V on the IGSW line and trace back if that is dead.

 

[SupraSean]

Ok, so i have no power to the igsw wire at the ecu, but i do have power at the ign fuse. i cant seem to find the diagram that shows where the wire goes from there, also i forgot to mention, the car will also not crank over. the starter doesnt engage. I am beginning to think they are interrelated. Thanks in advance


Edit: Just a thought, When the security system is activated for the starter kill. does it also cut power to the ecu? could that possibly be the problem? I'm Really starting to think its something stupid. because its the same harness that was in the car 6 months ago, when i pulled the motor out. Had no problems then.

 

[3p141592654]

Alarm does not control the ECU power, so that is not it. Not sure what year yours is, but the ignition circuit didn't change much. Here is a good starting point.

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=40

 

[Chambers]

Is connector B-1 connected properly? That would cause the starter not to energize and the ECU not get power.

 

[jetjock]

^ This. Since you have power at the fuse I'd be looking there.

You really should get another meter. Or connect test leads to the dog...

 

[SupraSean]

^ This. Since you have power at the fuse I'd be looking there.

You really should get another meter. Or connect test leads to the dog...

haha i managed to find an old tester. it seems to be doing ok for now. Connector b1, Where is that located on the car, i found something that says the big yellow plug by the ecu, but i would assume thats for pre 89, I have a 92 grey plug harness. Would it be in the same place i assume? Thanks for all your help so far guys, i really appreciate it. wiring is not so much my thing.

 

[3p141592654]

M1 is behind the glovebox. Connects engine harness to instrument panel harness. See this link.

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=28

 

[jetjock]

See 3p's link. B1 is near M1.

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=49

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=29

 

[SupraSean]

You guys are Great, really. That was it. She cranks over now, and i have power to my mapecu and wideband,, just gotta reset timing and im back on the road. Thank you guys so much. cant believe it was that simple...

 

[shaeff]

And thank YOU for actually posting the resolution to your problem, rather than trailing off and never letting us know if you found the issue.

Yes, JJ and 3p are collectively, "the man."

Edit: Chambers- nice work!

 

[jetjock]

1) Yep, thanks for posting.

2) Credit goes to Chambers

3) Schematics are good things.

4) 3p is quick to help. Me, not so much...

 

[SupraSean]

Car Cranks and i have fuel. Now i have No spark.. haha if its not one thing its another. This is a seperate problem btw
Thanks again guys

 

[SupraSean]

Ok so i'm at a total loss here. Fuel pump turns on. Got 40 psi in the rail. Got spark. No injectors are firing. Checked fuses. Injector resistor is connected. Any idea's here? This has driven me nuts all night. Btw as a side note it will run on starting fluid.