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ECU blown or fuel pump circuit?

2302 Views 7 Replies 3 Participants Last post by  Liam b1357
Hello all,

I have a 2002 WRX and I don't know how i could find out if my ecu is the problem. To start from the beginning, I was trying to find the output of my ECU that could turn it from automatic to manual in the hope of getting rid of p1596 error (automatic tranny diagnosis input signal high input).

I made the mistake of of removing the ECU from the bolts that i now know that ground the ECU. I tried cutting one wire (which i found out that was for the knock sensor.. wrong electrical diagram)

After i cut that wire, maybe 30 seconds later the car wouldn't start anymore. After re soldering the wire, i found that the fuel pump wasn't priming.
After troubleshooting everything possible with the fuel pump, i replaced it thinking that was my issue. It didn't. Still wouldn't prime. I have tested all the wiring from the fuse all the way to fuel controller. All is good.
I then thought to myself i will just bypass the whole line and wired 12 volt directly to the fuel pump to run it continuously to see if i could get the car started.

With the pump running and car turning over, i get no start now.
I assume that if the fuel pump is working now at full blast, will it drown the engine and prevent it from stopping?
How do i know if i blew the ECU?

thanks to anyone that can help me.
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Can you try to make an ECU controlled function operate? For instance, I believe that the ECU controls (or at least monitors) some of the HVAC controls. In romraider you can toggle polling via the defrost button, I therefore assume that if the ECU was toast that there is a chance that the rear defrost function may not work.

Similarly, the green test mode connector under the dash would cause the ECU to cycle power to the radiator fans and some boost controller (if I recall correctly) when powered.

Finally, the best route to check would be using some OBD diagnostic device. If this communication still works then the ECU still has partial function. It would be informative to check for DTCs too.
I didn't think of checking other systems. That's a good idea.
I have an ODB tester. I don't see anything out of the ordinary.

Can I swap the ECU with 2003 Impreza or is WRX ecu different?
I can get one from scrap yard for cheap.
I would rather not swap it to be honest, but its cheaper to go that route than getting car towed to mechanic.
well, it looks pretty bad.
Tried using my OBD scanner and it wont connect to ecu. My car also usually has engine light on for the p1596 code that i cant get rid of and now shows none.
I don't know of any functions that are controlled by the ecu that i could test with out engine being on.
wipers, heater, radio, windows, four ways all worked.
The fog lights didn't.
So, verdict?

secondary question, is the ECU from a 2003 impreza the same as 2002 wrx?

does the ecu have a fuse?
you may be able to test other ecu functions by connecting the green test connectors under the dash and turning the key to the on position. i believe that the ecu cycles some controllers under the hood when the test connectors are plugged together.

i don't know the answer about the ecu compatibility.

did your obd scanner fail to connect, or did it successfully read no error codes? the lack of error codes could simply be due to removing power from the ecu for a short period of time.
my scanner could not connect to ecu. I have a bluetooth one and it connect fine to the adapter, but I cant read anything from the ECU.

I don't understand what you mean by connecting the green test connectors.
Hey currently running into the exact same situation after installing my engine, besides the nock sensor, same story w the fuel pump too😭 did you manage to find a solution? im totally stumped. Fogs won’t turn on just like yours. Actually figured it out, new to the forum, so I don’t know how to delete
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