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Hacking up Honda's ECU
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PostPosted: Sat Sep 05, 2020 5:32 pm 
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Joined: Thu Aug 20, 2020 2:11 pm
Posts: 3
Hello,

a VTEC solenoid CEL pops few seconds (about 3 to 5 i think) after reaching 4800 RPM under hard acceleration. I don't know if the VTEC is being engaged as it's my first Honda with VTEC (probably it isn't engaged). I followed the steps from the service manual for CEL 21 and the conclusions are below:

1. The solenoid seems OK, I measured the resistance at 16 ohms, where the manual says the OK value is from 14 to 30 ohms (if I remember correctly)
2. When the ECU is plugged into the car wiring, there is short between GND and 1-pin solenoid connector (the manual says to repair the short in this wire at this step)
3. But when I disconnect the ECU, the short is gone, and connectivity test on both sides of this wire (from ECU side and from engine bay side) shows that it's ok

So I suppose that the problem is in the ECU. As I diassembled the ECU cover, I noticed that somebody already messed with it. The EEPROM, IC4, IC14 and some other parts were soldered again, as there are signs of soldering flux. Also some parts look like they were desoldered (HIC3, IC16, IC15). Also, there is a wire between A4 and D6 I think (if I understand correctly after reading posts on this forum, it is to emulate a VTEC engagement sensor (?) that can be installed in the car).

What would be the proper course of actions now? I read that the problem can be with a IC14 switch (SK 5151S on my board) and Q13 transistor. Can I check those parts without desoldering them?

I'm attaching photos of my ECU.


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PostPosted: Mon Sep 14, 2020 6:06 pm 
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Joined: Thu Aug 20, 2020 2:11 pm
Posts: 3
Well, there I fixed it :lol: .

I've been reading through this forum and suddenly it came to my mind that I have the wire from A4 to D6 on my ECU (which emulates the VTEC oil pressure sensor) and as far I remembered I also had the physical oil pressure sensor connected to ECU. I ran to the car and yes, there was sensor and sensor emulation connected at the same time :) . After unplugging the sensor, the CEL is gone and VTEC KICKS IN YO 8) .


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