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Old 03-27-2021, 07:27 PM   #1
Chuma87
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Default ECM fried?

Hi friends..

I've been playing hardwiring for walbro 255 fuel pump, and at one point I unintentionally short-circuited, all for not disconnecting the battery...

MY car..
Forester S-Turbo MY02, no fuel controller module...only ECM

I left everything original, but it only started once, then it never turned on again..

All the fuses were checked. Only fuse SBF-5 from main fuse box was burned, But I solved it by soldering with tin, momentarily.

The problem is that the original fuel pump relay does not turn on, and consequently, the pump does not turn on.

With a multimeter, I checked it ... and there is no signal coming from the ECM (B136 pin # 16) (image). It's supposed to get GND...But I can't find a connection with the chassis (continuity with multimeter). So that's why I guess it's GND


The B136 pin # 16 where does it get signal inside the ECU? What do you use as a parameter? ignitor relay? Ignition switch? Immobilizer module?

The momentary solution, for the fuel pump to work, was to change that cable, for a GND coming from the chassis
Everything works, but the fuel pump never stop priming when key is ON (previous start)...Is annoying

I can even read and write to the ECM with romraider, and read codes with ecu explorer

Have I fried part of the ECM?
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Last edited by Chuma87; 03-28-2021 at 04:11 PM.
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Old 03-28-2021, 04:26 PM   #2
Chuma87
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Update...

I was able to find signal from pin #16 of B136...
Before...the voltimeter negative (-) lead place on chassis , and voltmeter positive (+) lead from ECU signal pin...I couldn't find GND continuity.

So I swapped the leads, and was able to find the ECM signal, during its 2 seconds, and when engine runs.

But I do not understand why, once the plug is placed on the relay, I do the test and I don't find continuity ... only 12v ... It is as if the GND signal of the ECM is returning 12v ... Relay broken?

When i put de red multimeter lead on coil relay [1] (voltage comes from IGN fuse 15a)...I get only 11,88v, when de key is ON...is it low voltage?

Do I need 12v or more to drive the relay coil? I don't understand...Because, if i get GND from chasis, relay WORKS with those 11.88v...continuously priming, doesn't cut, like the ECM does...
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Old 03-28-2021, 04:40 PM   #3
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The ECM provides a switched ground path for the relay coil. If you are seeing 12V on that pin it is indicating an open circuit on the ground path so you read the voltage through the coil which is a low resistance. If that side of the coil were grounded as it should be you'd read zero volts or close (maybe a tenth or two). To confirm this you can unplug the relay and check the voltage at that ECM pin again and see if it is now close to zero.
If that pin never goes low when the pump is supposed to run, then either the output driver for the relay in the ECM is blown, or something else is wrong and the ECM is not trying to turn the pump on.
Maybe look at live data and see if anything is missing.
And put a proper fuse in before more stuff burns up. If the fuse keeps blowing then your problems go well beyond that relay.

Last edited by Mulder; 03-28-2021 at 04:47 PM.
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Old 03-28-2021, 08:19 PM   #4
Chuma87
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But with relay connected, key switched to ON, multimeter measuring V on pin 3 (picture), returns 12v~...It makes believe that the 12v comes from the ECU (B136 / 16)


But with the connector disconnected from the relay, multimeter measuring continuity, black multimeter lead on pin # 3, and red multimeter lead on chassis ... The multimeter tells me that it is GND, coming from ECM during the period that it decides (2 seconds ) for fuel pump priming...So, the GND signal comes out of the ECM, consequently, the ECM is not fried, ok or am I wrong?

If with the relay connected, the same pin [3] returns 12v, but disconnected it works as it should (GND signal for 2 seconds from ECM) ... Wouldn't the relay be suspicious?

Another worrying factor is the pin [1]. With the car in contact, it receives from the IGN fuse (fuse box), only 11.80v ~ in the green connector (B46) ... Following that cable (going back to the power source), I get to the ignition switch (Green wire), there is 12v ~ there, I manage to locate the cable that feeds the ignition switch (White wire) ... Following it, I get to the SBF-4 50A (engine bay fusebox) which has 12.22v ~ the same as the battery . With this I say, that I have a loss of 0.30-40v on the road. Could it be that those 11.80 ~ 11.90v cannot drive the coil? and that the 12v coming through pin [2] is overloading / shorting inside the relay?
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Old 03-28-2021, 09:56 PM   #5
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I think the ECU needs to see the crank sensor signal at least to verify the engine is turning. It is part of the safety system to turn off the pump operation if the engine isn't running. The ECU turns on a circuit inside it that makes the ground connection for the pump relay coil. You may have 12 volts on the pin while it is not working. I have repaired older ECU's with this kind of problem in the past. The pin tied to a driver IC that had failed. Replacing the IC fixed the problem. I suspect your ECU has the same kind of issue.

In post 4 you seem to be saying that the ECU pin shows a ground when no load is connected to the pin but doesn't show a ground when a load is connected. If that is the case then the driver inside the ECU is faulty. An easy way to check the operation is just check the voltage with things connected normally. When the pump is supposed to be operating you will see little voltage on the pin (indicating a near ground potential). If the pin stays near 12 volts then the switching isn't happening inside the ECU (bad).

The measured voltage below 12 volts you saw going to the relay isn't a concern. It is just the result of normal wire losses you were seeing. The relay would most likely still work even if the voltage is around 9 volts. The only way pin 2 could be shorted is a ground to touch that pin or have a shorted condition on pin 4, that ties to the pump. Things would be fine until the relay closed and then the fuse would blow out when the relay contacts closed.

Last edited by Cougar4; 03-28-2021 at 10:17 PM.
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Old 03-29-2021, 08:15 AM   #6
Chuma87
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Hi Cougar4...

What is "IC"? Ignition Coil?

I don't understand why with the relay disconnected, the ECU sends GND signal accordingly, but when the relay is connected, it doesn't ...

Its a LHD...ECM is located on passenger side, main relay and fuel relay on driver side.
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Old 03-29-2021, 11:15 AM   #7
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IC stands for integrated circuit. It is one of the circuit chips inside the ECU. From what you stated earlier about the operation it seems the output of the chip is bad. It can't support the load it is supposed to operate, the relay coil. The current needed to run the relay has to flow through the IC. It is acting like a switch. I suspect that if the chip was replaced the ECU would be fine.
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Old 03-29-2021, 12:18 PM   #8
Chuma87
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Quote:
Originally Posted by Cougar4 View Post
IC stands for integrated circuit. It is one of the circuit chips inside the ECU. From what you stated earlier about the operation it seems the output of the chip is bad. It can't support the load it is supposed to operate, the relay coil. The current needed to run the relay has to flow through the IC. It is acting like a switch. I suspect that if the chip was replaced the ECU would be fine.
But the output (B136/16) works fine, if the relay is disconnected. It is rare that if the relay is connected, it does not work ...
EDIT
Quote:
I can even read and write to the ECM with romraider, and read codes with ecu explorer
If the IC is fried, could I test-mode the green connectors? Because everything about the ECM works for me...

EDIT:
RESUME:
B46 connector with relay unplugged.
-Searching GND signal from ECM.
Multimeter on continuity, black multimeter lead on chassis, red multimeter lead on ECM signal, key switched to ON...NOTHING
Multimeter on continuity, red multimeter lead on chassis, black multimeter lead on ECM signal, key switched to ON...2 seconds of "piiiiiiiiiii" from multimer = found GND signal from ECU.
-Searching V from ECM (low Voltage)
Multimeter on "20v", black multimeter lead on chassis, red multimeter lead on ECM signal, key switched to ON...4~4.5v found on that pin.

B46 connector with relay plugged.
-Searching GND signal from ECM.
Multimeter on continuity, black multimeter lead on chassis, red multimeter lead on ECM signal, key switched to ON...NOTHING
Multimeter on continuity, red multimeter lead on chassis, black multimeter lead on ECM signal, always "piiiiiiiiiiiiiiiiiiiiiiiiiiiii" (found GND) whitout switch key to ON.
-Searching V from ECM (low Voltage)
Multimeter on "20v", black multimeter lead on chassis, red multimeter lead on ECM signal, key switched to ON...12~12.2v found on that pin.

The mistake I had made so that the fuel pump relay did not work now

Last edited by Chuma87; 03-29-2021 at 11:20 PM.
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Old 03-31-2021, 02:53 PM   #9
Cougar4
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The IC that controls the fuel pump relay most likely has several outputs that control various devices, including the FP relay. That output has been damaged somehow. I suspect that the voltage should be close to battery voltage on that pin when it is isolated and not turned on to run the relay. This is just like a open switch would be that has the load tied to it in a circuit and the other side of the switch is tied to ground. When the switch is closed then the ground is connected to the load and would turn on the relay. The IC has to be able to handle the current needed by relay coil in order for the FP circuit to work. Check the voltage on the pin while the load is disconnected and the pump is supposed to be running. The voltage should be close to zero volts, indicating it is at ground potential. If it isn't near zero volts the connection to ground is bad. The IC has a bad output port.

Your connections shown in the drawings to the relay are wrong, if that is the way you have things wired. If battery power is tied to pin 30 then the FP power lead needs to be connected to pin 87, or 87a if 87 is the normally closed contact connection. I think 87a is the normally closed position (connection to pin 30 when the relay is OFF). Pin 87 and 87a work oppositely from each other and pin 30 is common to both pins, but only one pin is tied to 30 at a time, depending if the relay is either off, or on. Pin 86 would tie to switched power and pin 85 would tie to the ECU lead that controls the relay operation, which makes a connection to ground to turn on the relay. Hopefully when the wire connections to the relay are corrected the ECU will work okay and it isn't damaged internally.

Last edited by Cougar4; 03-31-2021 at 03:22 PM.
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Old 03-31-2021, 03:17 PM   #10
Chuma87
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If the IC is burned out, how is it physically? because I didn't see anything on the ECM board that is burned out ...

Quote:
Check the voltage on the pin while the load is disconnected and the pump is supposed to be running..
You mean...key switched to ON, check the voltage on GND signal (B136 pin#16)....With the FP relay connected/plugged:
Quote:
B46 connector with relay plugged.
-Searching GND signal from ECM.
Multimeter on continuity, black multimeter lead on chassis, red multimeter lead on ECM signal, key switched to ON...NOTHING
Multimeter on continuity, red multimeter lead on chassis, black multimeter lead on ECM signal, always "piiiiiiiiiiiiiiiiiiiiiiiiiiiii" (found GND) whitout switch key to ON.
-Searching V from ECM (low Voltage)
Multimeter on "20v", black multimeter lead on chassis, red multimeter lead on ECM signal, key switched to ON...12~12.2v found on that pin.
With the FP relay disconnected/unplugged...what I quote below:
Quote:
B46 connector with relay unplugged.
-Searching GND signal from ECM.
Multimeter on continuity, black multimeter lead on chassis, red multimeter lead on ECM signal, key switched to ON...NOTHING
Multimeter on continuity, red multimeter lead on chassis, black multimeter lead on ECM signal, key switched to ON...2 seconds of "piiiiiiiiiii" from multimer = found GND signal from ECU.
-Searching V from ECM (low Voltage)
Multimeter on "20v", black multimeter lead on chassis, red multimeter lead on ECM signal, key switched to ON...4~4.5v found on that pin.
Quote:
Originally Posted by Cougar4 View Post
Your connections shown in the drawings to the relay are wrong, if that is the way you have things wired. If battery power is tied to pin 30 then the FP power lead needs to be connected to pin 87, or 87a if 87 is the normally closed contact connection. I think 87a is the normally closed position (connection to pin 30 when the relay is OFF). Pin 87 and 87a work oppositely from each other and pin 30 is common to both pins, but only one pin is tied to 30 at a time, depending if the relay is either off, or on. Pin 86 would tie to switched power and pin 85 would tie the ECU lead that controls the relay operation, which makes a connection to ground to turn on the relay.
From the picture, the two connections with the alternative relay (A or B), are the ones that I used and that may have been the ones that caused the current failure of the car. After that, I went back to the original relay and it doesn't work. But if I get the GND from the chassis, it works,



Is it possible that the GND is "weak" and that is why the 12v passes?

Last edited by Chuma87; 04-01-2021 at 07:42 AM.
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Old 04-01-2021, 07:44 AM   #11
Chuma87
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I will make a video so that you understand the problem ...

I checked again the ECM and its components, following the PIN of B136 / 16 ... and inside, there is an SMD 000 resistor, and then it ends in some type of transistor named GA 07 ... until there, all the way is healthy, after the transistor would not know since I measured everything without power.
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Old 04-01-2021, 11:42 AM   #12
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I think I completely understand the problem you having. I will say it again, if you connected things up using either drawing A or B, you have wired to the relay incorrectly. It won't work the way you have shown it in the pictures. For a correct drawing of the relay see the link below. The coil of the relay ties to pins 85 and 86. One of the pins needs to connect to switched power and the other pin needs to tie to the ECU wire, which supplies the switched ground connection. Your pictures show pin 85 is tied to the pump power lead, EL WRONG OH. Using your drawing as reference, the pump power lead needs to tie to pin 87 of the relay. Swap the wires shown in option 'A' going to pins 85 and 87. If the ECU is still good the relay will work as advertised.

The resistor you saw is a zero ohm resistor, basically just a wire. The transistor acts as the switch, that is either ON or OFF, to activate the relay or turn it off. When the transistor is ON the connection to ground will happen, turning on the relay, the voltage on the ECU pin will be near zero volts, indicating the connection to ground (no voltage potential).

https://lh3.googleusercontent.com/pr...loK5S0Jue3JP5E

Last edited by Cougar4; 04-01-2021 at 04:16 PM.
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Old 04-02-2021, 08:46 PM   #13
Chuma87
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UPDATE:

A friend from the Subaru Argentina Club was helping me. I did the test with the ECM open, and I checked a MOSFET ... there is one that enables the GND signal ... it seems that it broke, since the positive signal reaches the gate (I suppose that what I measured was gate) of 5v during two seconds, with the key ON.



The mosfet is called GA 07 (it says that at the top). Does anyone know the replacement?

Last edited by Chuma87; 04-03-2021 at 12:38 AM.
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Old 04-02-2021, 10:34 PM   #14
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Assuming the transistor is a MOSFET this one may work as a substitute:
https://www.ebay.com.au/itm/20PCS-HE....c100935.m2460

Last edited by Cougar4; 04-03-2021 at 05:51 PM.
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Old 04-04-2021, 11:04 AM   #15
Cougar4
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Looking over your option A diagram again makes me think when things were hooked up that way is when the ECU got damaged. I think the power tied to pin 86 and the pump on 85 allowed the relay to turn on, thus connecting the battery on pin 30 to connect to pin 87 and to the ECU connection. When the ECU turned on the transistor that caused a direct short and burned out the transistor.
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