Hey, after thinking my VAFC stopped working, turns out my ECU isn't getting power. Finally got my new multimeter today and checked voltage to the power wires and nothing. What do you guys think is wrong?

BTW, this all happened right after I installed my VAFC. It worked for about a day and then no power. The VAFC does still worke when I tested it out on the battery.

 

I would check fuses, clutch switch (mt), then main relay.

 

Hopefully if you did wire it wrong, it would have blown the ecu fuse. If it is blown, I would recheck your wiring. Chances are, its not just a once and a life time issue or an intermittent one.

Other than that wires feeding your ecu maybe, or the connector/pins. What color of wires you checking for power on in your connectors?

Id pull the lid off your ecu and than the bottom cover, and look for burn marks too. Look very carefully. Do a visual check of the components. You have a multi meter you can electrically check components with some help from H-T.

 

check the ecu ground its on top of the thermostat housing

 

Oh yeah! thats a good one too x2

 

^^
x3

 

Checked fuse, ground, and voltage and nothing. The ground is around the vtec solenoid area right? I'm stumped right now and have no clue what the problem is. What else can I check for?

 

If i have a fried ECU, would the power wires still have voltage going to them or would power cut off?

 

This problem happened after I tried plugging in the VAFC while the car was running...

Bump

 

Swap ecu's with someone and see if theirs works.

 

So I took power from my battery and attached it to the VAFC to see my volt readings for pressure and throttle. They come out to be nothing which makes me believe that the cause has something to do with my harness. What do you guys think it can be?

 

Also checked main relay. It clicks but there is still no power to the ECU wires. The ECU looks fine and I'm stumped . BTW, the main relay only clicks once.

Would the ECU harness still get power if the ECU was fried/unplugged?

 

you know there's two ECU fuses, right?

 

The 2 under-the-dash or am I missing one?

 

you got em.

so it's just the ECU that's not getting power? Everything else works ok, fuel+temp gauges, radio,etc?

 

Yep, everything but the ECU. Could it be possible the wire burnt out? As in got a short somewhere so there is no complete path?

 

Is it possible to take power off a fuse and cycle it to the ECU safely? I'm, stumped and most people I ask don't know either. Any help would be appreciated. Car's been sittin for over a month now

 

Bump for a Prelude that's down

 

Is it true that if the ECU doesn't get any power/readings from one of the sensors (I.E. MAP) that it won't receive power?

 

Could I get some other 12v power source and just cycle it to the ECU?

 

Thanks for all the help guys!!!

After about a month of diagnosing, I finally found the problem! The #1 terminal on the main relay connector wasn't getting battery voltage so I just took a wire from the battery and added a fuse to it and connected it and car started right up!

 

Did you trying resting it... Like disconnecting thwe batterry and ecu then connectign everything back together? But, then again I could be wrong...

 

What do you mean? I already have the problem fixed lol

 

Thanks for posting that main relay diagram, I have the helms and I cant even find any pinout for it.

I'm not sure whats going on with my car, all voltage is good until the relay. Havent tested anything after that but I hear no clicking in the relay and the fuel pump doesnt prime. I took it out and all the solder joints are good. Even if the voltage was low it should still work? Car has been sitting for a while but the battery certainly isnt dead.

 

So if I'm reading this right when 4/6 gets power from the ignition after you turn the key to start, 7 the fuel pump should have a ground now thereby priming the fuel pump. Maybe the lack of voltage isnt enough to trigger that relay arm to swing over, going to test now.


Modified by TraKtioN at 8:07 PM 8/15/2008