Awkward problem, ECU will not turn on...Kinda
 

Here is what makes this so awkward. When i plugged my scantool in the ECU turned on and the car started.

Ive checked my ECCS fuses they are good, the signal for the ECU is there but it will not turn on when commanded by the ignition switch. and a new problem i have run into the fuel pump has stopped working i think it is related to the ECU not turning on. Ive tried spare ignition switches and ECUs what else could be the problem? I wanted to say the ignition relay the other ignition related gauges also cut on so im not sure if that would really be the issue.


Edit: Problem found. Main grounds on the intake manifold were disconnected.

Maybe the screw hasn't been turned back to the RUN position?

i never touched the ECU but i'll check

I can't understand why the car started with the scan tool plugged in. There are only 4 wires going to the connector, 12 volts (pin 1), two grounds (pins 12 & 13) and the data line (pin 10). I don't know if a scan tool can send a "start engine" command to the ECU. Or CONSULT.

The ECU has 12 volts on several pins. Pins 67 & 72 via the ECCS relay; pin 24 via the ignition switch in the ON & Start positions, and pin 80 direct from a fuse.

If the ignition relay were bad, there are a bunch of things that won't get power/won't work and the car would not start. The gauges are among that group, some of the other things are warning/idiot lights, turn signals, door locks, comm system, alternator and more.

FYI - the ignition relay is to the left of the fuse block in the dash. It is the middle of the 3 relays there.

:laugh: see my pickle. The ECU will turn on only with the scan tool plugged in then i can start the car.

I figure it has to be like a blown fuse or connector that is disconnected because it does not make sense that the ECU will only turn on with a scan tool plugged in.

I was just completing an interior swap and my car was starting no problems before i started, I have taken the dash back out and inspected the E106 connector the front and back of the "super junction" everything back there is fine along with under dash the fuse box. I ran my main battery line under those connectors so i was wondering if i knock out or snap a wire and everything is good.

I checked the relay and it looks brand new actually. I moved the blower motor relay to the ignition spot just in case.

But i have checked pin 24 and its getting the 12V from the ignition switch, so i have to check the rest when i get the battery hooked up again. I haven't checked the rest but it could be that something happened to one of those power lines to the ECU and the scan tool being hooked up bridged the connection. I'll check the other pins to see if they are getting power or if continuity is the problem.

I don't have a good understanding of what goes on inside the scan tool. The 12 volts on the connector is there as part of the OBD standards/protocol. Its purpose is to let the scanner know that it is connected to a car. I don't know if a scanner is allowed to use the 12 volts to power the scan tool.

Would you clarify one thing for me? I don't understand what you mean when you say "turn on the ECU".

By turn on, when the key is in the on position and i plug in the scan tool the check engine light comes on, my emanage turns on and the fuel pump primes.

Question though i know the are important but just how important are the grounds on the Intake manifold i notice they were not attached? :nervous:

^ Crusher, you done fckd up real good this time. :lmaoo:

That's the main ground for the ECU, fuel pump, a buncha important-ish

Somehow it's grounding to your scan tool, thus why it's alive.

I messed up in extending one of the wires during the white nightmare's DE-K swap, that's why the fuel pump wouldn't run.

Oh well, I hope that fixes it. :rofl:

Good news is, i broke more interior pieces that i now have to replace and i got to check out all my fuses and make some improvements here and there :woot:

I'm glad I don't have to suggest gas and matches as the fix.