ECU blown or fuel pump circuit issue?

[sfortin]

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.

[Fairtax4me]

If you cut wires with the ECU still plugged in or unplugged the ECU with the battery still connected, its probably cooked.

 

The knock sensor wire is shielded. Has a grey outer insulation and a braided sheild section outside of the insulation for the signal wire. Did you cut through the shielding, and did you solder the shielding to the signal wire when you tried to repair it? The shielding is grounded and needs to be kept separate from the signal wire.

[1 Lucky Texan]

if you think the engine is now flooded, try starting with the gas pedal held to the floor - that causes the ECU to go into 'clear flood' mode.

 

could the security system is preventing start(?) try lock/unlock with the key fob.

[sfortin]

i cut the wire coming out of the ECU. it isn't a shielded wire. From what I can see from the wire diagram, the  knock sensor has another wire coming from the ecu for the shield.

 

Someone else told me that the ECU is not grounded through the bolts that hold it in place. I think IU wasn't careful when working with the ECU (few too many beers I think ). Live and learn, that's my goal.

 

How could I tell that my ecu is toast?

 

I ran the fuel pump and since it turned over but no start, the only things I messed with kind of tells me this.

 

What do you think?

 

I don't see how the security would stop car from starting. I make sure everything is unlocked. Anything else i'm missing here before I replace the ECU blindly?

[1 Lucky Texan]

are you able to scan the ecu for DTCs ?

[Numbchux]

No, the ECU is not grounded through it's mounting bolts

 

I don't see how cutting one wire and soldering it back together could cause failure. Did you unplug anything else during the project? 

 

 

Get your hands on a code reader, and see if you can communicate with the ECU. See if there are any diagnostic codes. (I assume you should still have an OBD II port on canadian cars).

[sfortin]

I will scan it tonight and see if i can do basic things with the car that the ecu would control.

I will post back the minute I know some more.

 

I didn't un plug anything else during this. I did try and troubleshoot everything else in the fuel circuit such as the relay, the controller, the fuse and the pump itself. Check continuity in the entire line, power to the pump. Everything looks fine.

 

That's why i decided to bypass all of that and try and get the pump working and starting the car. I thought, if car would start, pretty much would mean the problem was in the fuel circuit. But no start points to the only thing that is left, the ECU.

[Numbchux]

That's not the only thing left. There are many things that can cause the ECU not to try to start the car (you're diagnostic was correct, though, in ruling that it is not the fuel pump relay, or, at least, not just the relay).

 

 

I've seen a bad crank sensor cause the ECU not to prime. But don't try to guess the old fashioned way, get a code reader plugged into it (frequently can be rented from an auto parts store, I have a bluetooth OBD II dongle that cost less than $20 and allows me to use my phone). See if the ECU is powering up at all (if you can connect to it), then see if there are any trouble codes, and then monitor the rpms and crank it over.

 

 

You have a lot of steps before you need to buy a new ECU.

[86BRATMAN]

When you turn the key to the on position does the cel turn on in the cluster?

[sfortin]

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?

[86BRATMAN]

You could be looking at a fuse, there are a couple different ones that it could be, check both the under hood and cabin fuse boxes for blown fuses. I've also seen a blown main relay cause symptoms like this as well.

[Numbchux]

When you turn the key to the on position does the cel turn on in the cluster?

 

This

 

 

 

It sounds like your ECU is not powering on. Start with checking all the fuses. Then get a multimeter or test light out, and your ECU pinout, and check all the power supply wires for power.

 

 

If it comes down to a new ECU. It DEFINITELY has to be for a WRX, not just an Impreza. I know that only the 02 WRX AT ECU is identical to yours, but it's possible that other 2.0l GD WRX ones could work, and maybe even STi.