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Hacking up Honda's ECU
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PostPosted: Wed May 27, 2015 8:38 am 
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I can't get my 90 Integra started. The first thing I did was check the main fuel relay as I am not getting the typical click and 2 second fuel pump prime, but I can hear the start relay (aftermarket one installed due to a auto to manual transmission conversion) clicking. I've checked and swapped out the main relay, checked all fuses, removed and cleaned out the ignition switch, checked out the ECU wiring harness as best as I could and still nothing. I'm looking at the factory service manual but the procedure assumes that I have a test harness. It's calling to check voltage/continuity at certain locations (ie A7, A8, A23, A25, B1) on the test harness. Of course I don't have a test harness and I've spent the last two weeks on and off trying to figure out what pins those codes relate to. I'm not sure if I'm understanding it but I'm assuming A stands for the A connector, but what I can't figure for sure is what pins are what exactly. Looking at the A slot/connector it only looks like there are 18 pins at that connector. What are A23 and A25 on this particular ECU? Most charts that I look at that have these spots look like vtec ECUs.


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PostPosted: Wed May 27, 2015 5:27 pm 
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Location: seattle washington, usa
try this. http://civic.gotskillslounge.com/civic% ... Pinout.png

Its for a PM6 but should be the same. A1 on the test harness is the same as A1 on the ecu and so forth.


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PostPosted: Wed May 27, 2015 5:42 pm 
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Thanks. I actually have that already. The FSM says to test A7 and A8 but according to that chart A8 is blank? Looking at the harness there is a wire in that spot but I have no idea what that wire is for. Also, I'm still trying to figure what the A23 and A25 are. That link doesn't show anything higher than A18.


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PostPosted: Wed May 27, 2015 6:46 pm 
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do you have an obd0 pr4, or obd1 pr4? Sounds like you have an obd1; try this: http://technet.ff-squad.com/wiring.obd1.htm


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PostPosted: Thu May 28, 2015 8:54 am 
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It's definitely a OBD0 PR4:


Image

Image

Image


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PostPosted: Thu May 28, 2015 9:46 am 
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yep, definitely obd0. Obd0 only had 18 pins on the "A" connector, maybe your book is referring to an obd1, thats why they are testing on A23,A25. The DA's came in two versions, obd0 and obd1, the change can be found as early as late 90, so I have many service manuals for the wrong production date get may people lost. Let me look through my stuff and see what I get.

A8 goes to EGR only used on automatic transmissions.

edit:

Try this: If you can read wire diagrams, you shouldn't need the diag. tree in your book. If you can't read diagrams I guess I will write you a test procedure off those schematics.
Attachment:
OBD0 PR4 PGMFI DIAGRAM.gif


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PostPosted: Thu May 28, 2015 10:27 am 
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By God I think you got it. North American Da's were OBD0 from 90-91 then switched over to OBD1 in 92-93. Plus in 93 the GS-R came out with the 1.7 vtec (first ever variable cam timing production car at the time). This helps a ton. I have a Chilton that has a similar diagram but all it shows are the wire colors that lead to a square box labelled ECM but there
are no pin labels shown anywhere.

Thanks man, you have no idea how much I appreciate you looking and posting that up. Like I said I've looked high and low online and wasn't able to find the right one. I finally posted inherently of desperation. My last resort was to manually trace the wires and make up my own chart but that would have taken me forever.


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PostPosted: Thu May 28, 2015 1:07 pm 
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Location: seattle washington, usa
no problem. I was a Honda dealer tech for near a decade and have since moved on to higher tasks, so I have lots of this kinda stuff around. If you have any problems I should be able to walk you through it.

On a side note, yes the B17 did come out in 92, but the B16 was the first VTEC . Released in 1989 in the SIR's, it was the first ever factory engine to produce 100hp per liter at 160hp stock. I think some later versions produced close to 180hp. If I remember correctly, the B17 also had a reputation of head gasket problems and was quickly replaced with the B18C, however the B17 has recently become sought after by some DA owners looking to remain period correct in there swaps. Wow, I guess I sound like an encyclopedia, sorry for that.


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PostPosted: Thu May 28, 2015 1:33 pm 
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I forgot about the B16. But wasn't it only available in Japan to start? I could be wrong but maybe I'm thinking the B17 was the first vtec type system in North America? The B16 came later in Civic SiRs a year or two later? Anyhow, I'm stuck with my plain old boosted B18A1.

Thanks again!


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PostPosted: Thu May 28, 2015 2:36 pm 
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ya, the B16 was infact in japan first. It cam to north america in 96 in the del slow, ehm, excuse me, the del sol. The B18A1 is still good, I am using a boosted one in a 94 civic EX stripped down to a DX with a sunroof.


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PostPosted: Thu May 28, 2015 6:05 pm 
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Would you happen to have the FSM fuel relay and fuel supply system test procedure would you? My version of the manual says to also test the voltage between A23 and A25/B1. Which from what I can tell are for the ignition power and ground (A12/A14 and B3 on the OBD0 PR4 if I'm reading it right).


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PostPosted: Thu May 28, 2015 7:20 pm 
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okay, sorry for the delay, I was out for a bit. I hope this is what you're looking for. As you can see pin3 of the main relay goes to pins A13 and A15 of the ecu.



NOTE:

If the car stands and continues to run, the Fuel Pump Main Relay is GOOD.

Fuel Pump Main Relay Location
Attachment:
PR4 main relay.gif



1.Remove the Fuel Pump Main Relay from under the dash. It is to the left of the steering wheel, mounted on the back of the fuse panel.

Main Relay
Attachment:
PR4 main relay 2.gif


2.Attach battery positive voltage to the No.4 terminal and battery negative voltage to the No.8 terminal of the Fuel Pump Main Relay. Then check for continuity between the No.5 terminal and the No.7 terminal of the Fuel Pump Main Relay.
a.If there is continuity, go on to step 3.
b.If there is no continuity, replace the relay and retest.
3.Attach battery positive voltage to the No.5 terminal and battery negative voltage to the No.2 terminal of the Fuel Pump Main Relay. Then check that there is continuity between the No.1 terminal and No.3 terminal of the Fuel Pump Main Relay.
a.If there is continuity, go on to step 4.
b.If there is no continuity, replace the relay and retest.
4.Attach battery positive voltage to the No.3 terminal and battery negative voltage to the No.8 terminal of the Fuel Pump Main Relay. Then check that there is continuity between the No.5 and the No.7 terminal of the Fuel Pump Main Relay.
a.If there is continuity, the relay is GOOD.
b.If there is no continuity, replace the relay and retest.


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