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Old 05-09-2021, 06:29 PM   #1
Moose5280
Scooby Newbie
 
Member#: 523432
Join Date: Apr 2021
Chapter/Region: RMIC
Location: Denver, Colorado
Vehicle:
2001 Impreza RS

Default Help Testing an ECU for an 04/05 WRX engine in a 2001 RS

I apologize for the verbose question. I purchased a 2001 RS as a project car for my son and I (it’s his high school graduate gift). The prior owner tried to install a 04/05 WRX engine but had issues with the wiring merge. We started with new engine and dash wiring harnesses and completed the merge. We tested along the way and performed a final end-to-end test of every wire, along with power and ground verification. The car came with 2 ECUs and I created a test harness with the main relay (MR) and data link connector (DLC) to evaluate the ECUs via a scanner with the following wiring:
- 12 VDC through a 15 amp fuse directly to ECU pin E10; to pins 5 and 6 of the MR; and to pin 1 of the DLC
- Ground directly to ECU pins A7, A15, C22, C1, to pin 1 of the MR, and to pins 12 and 13 of the DLC

The other ECU pins are as follows:

- A21 to DLC pin 10 (SSM/GST comms)
- E2 and E3 to MR pin 3 (power to control unit of the EUC, fuel pump, and various sensor)
- A6 to main MR pin 2 (to actuate the MR)
- A5 via toggle switch (switch 1 to simulate ignition on) to 12 VDC
- A16 via a push starter switch (switch 2 to simulate ignition start) to 12 VDC

ECU1: Denso 6G 22611AH791

ECU2: Denso B7 22611AJ890

Results

Stage 1: apply 12 VDC
- Everything seems fine and the code reader is powered

Stage 2: ignition to on via turning on switch 1
- The main relay is actuated
- ECU1 response: the main CPU (assuming the large chip) is slightly warm but the code reader is unable to communicate with the ECU. The heat sink (on the side) eventually gets hot to the touch. As a hail marry, we thought maybe ECU1 needs to be hooked up to the car to communicate with the code reader, but when we turn the ignition to on, fuse 11 to the ignition coils immediately blows – ECU pins D21-24 are all 12 VDC. So we disconnected all but one ignition coil, replaced the fuse, and that ignition coil began to get hot, so we stopped the test (hopefully we didn’t fry them). We tried ECU1 with the test harness and verified that D21-24 are all 12VDC, not 0 as indicated in the manual. We also triple checked the car wiring.

- ECU2 response: the heat sinks and the CPU get extremely hot within seconds and the code reader is unable to communicate with the ECU. So I am assuming ECU2 is toast.

Stage 3: ignition to start via pushing switch 2
- Did not try this

Question 1: can I test the ECU via our test harness and should the ECU communicate with the code reader with our setup?

Question 2: Are both ECUs toast?

Many thanks in advance for help, feedback, pointers, and guidance.
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Old 05-10-2021, 09:53 AM   #2
Cougar4
Scooby Guru
 
Member#: 53443
Join Date: Jan 2004
Location: Anchorage, AK
Vehicle:
2001 LL Bean Outback
Winestone

Default

I am wondering why fuse 11 blew out, especially since you stated that the ECU pins had 12 volts on them. It seems that you have made the correct wire connections so I think you may have to get a known good ECU that is meant to work in the wiring conversion you have done. I think the reader should communicate using the setup you have done. You should be able to get a replacement ECU for not too much of a cost.
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Old 05-12-2021, 08:53 AM   #3
Moose5280
Scooby Newbie
 
Member#: 523432
Join Date: Apr 2021
Chapter/Region: RMIC
Location: Denver, Colorado
Vehicle:
2001 Impreza RS

Default

Quote:
Originally Posted by Cougar4 View Post
I am wondering why fuse 11 blew out, especially since you stated that the ECU pins had 12 volts on them. It seems that you have made the correct wire connections so I think you may have to get a known good ECU that is meant to work in the wiring conversion you have done. I think the reader should communicate using the setup you have done. You should be able to get a replacement ECU for not too much of a cost.
Thank you, I just bought another ECU and will try it today using the stand alone test setup before hooking it up to the vehicle, fingers crossed.

Fuse 11 blew because the 12 V signal simultaneously and continuously actuated all 4 coils on the plugs instead of via a alternating wave. When the engine is not running, those channels are supposed to be 0 VDC.
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