1998 Civic Hatchback CX with D16Y8

My brother bought this car from previous owner “J” not running. Got the car towed to my house. It took a while when I first got the car to start it. Another issue to the problem was that the owner before J had put an OBD1 engine in the car along with an OBD1 engine harness & cabin harness (don’t ask why b/c I have no idea). J decided to take out the engine & put a Y8 in the car along with a junkyard cabin harness & engine harness. Upon my inspection it looks like there are some cabin plugs that are left unplugged.

There was a solid CEL at all times. First I tried a new main relay but, that did not solve the issue. I was not aware of how you should troubleshoot this so I just went out on a limb & bought a new ECU which solved the issue & started the car.

A year later the car is still having the same issue starting. I have another ’97 Civic Sedan that I have borrowed the ECU from & started it before. Well, now recently I am getting a solid CEL with a known working ECU from the ’97 Sedan. I also tried the relay from the ’97 as well with no luck.



The past few days I have tried troubleshooting the fuel supply system with the Service Manual I found online.

-Fuse 13 has power & is good. Fuse 44 has power & is good.

-I ruled out the Main Relay because I pulled one from a working car as well as the ECU.

Troubleshooting Step Per Service Manual:

-Check continuity between main relay connector terminal No. 3 & body ground. = Continuity present

-Measure Voltage between main relay connector terminal No. 7 & body ground. = Voltage Present

-Ignition Switch ON measure voltage between main relay connector terminal No. 5 & body ground. = Voltage Present

-Turn ignition switch to START position, with clutch pedal depressed, measure voltage between main relay connector terminal No. 2 & body ground. =Voltage Present but there was only around 5 volts if I remember? Is that the correct amount of voltage?

-**This step is where I got lost: Disconnect the A connector from ECU, check for continuity between main relay connector terminal No. 1 & ECM/PCM connector terminal A16.**

I DID NOT GET ANY CONTINUITY FROM THIS TEST. : So the manual says to repair open in the wire between the ECM/PCM (A16) & the main relay.

This is a dumb question, but don't you just put one prong from the multimeter to A16 (FLR) on the ECU connector & the other prong to No. 1 connector on the main relay harness to test the continuity there?

The wires look exactly the same (Green/Yellow). So I looked at my wiring diagram & it looks like it goes from A16 to main relay terminal 1. I tried to splice those wires together but still had no continuity. Isn't that the same exact wire? The A16 wire looks like it goes from the Ecu then to a neon green connector then up into the dash so I cannot trace it fully.

But, if I am understanding correctly, there should have to be power going to the main relay in order to send the signal to the ECU for the FLR (A16) correct? Unless it is the complete opposite where the ECU is sending a signal to the main relay? Either way the ECU is not getting power.

I also went to the next step :
-Measure voltage between ECM/PCM connector terminals A11 (IGP1) & A10 (PG1). NO VOLTAGE. Also measure voltage between A24 (IGP1) & A10 PG1). NO VOLTAGE.

So I am lost on what to do at this point. I just got the conclusion that if the main relay is not getting power to IGP1 or IGP2 then the main relay is not going to give the signal to the fuel pump to prime.

What should I do? I feel like I have to pull the dash to see if the wiring is broken somewhere.

 

There should be nothing left unplugged.

 

Yeah I thought so..but since the car has started before without them connected I do not think that is my issue.

If I have checked fuses for the fuel system supply & they check out, would you think there is a break in one of the wires since power is not present at the ECU & main relay?

 

What is left unplug?

 

No you should be getting 12v


This needs to be fixed, you have an open wire.


Yes this is how you would test for continuity



No, pin A16 from the ecm sends a ground signal to the main relay to activate the relay to turn on the fuel pump.

In order for you to correctly check this you need to do it with the main relay plugged in and the key in the on position.

 

Have you checked the engine harness grounding point at the thermostat housing ??? Making sure that ground is clean and solid is crucial for proper engine operation. A poor connection WILL illuminate the CEL solidly and the fuel pump will not prime. This may "seem" like a bad ECU.

 

Yes. That was one of the first things I did. I sanded it down as well as the ground for valve cover & tranny ground.

 

I am not 100% sure but it looked like a small brown connector under the steering wheel. Kinda looks like the service connector that you jump to get CEL on OBD1s.

 

-Okay I will try that,.

 

This is the diagram I made from looking at the helms manual.

From the diagram it looks like the A16 wire & the No. 1 Terminal Connector are the same wire. I tried to just jump those wires together at the A plug for ECU & Main Relay but still had no luck. Or is that incorrect?

 

Diagram looks correct. Yes those are the same wire. you need to check that the ecu is trying to ground this wire when you first to the key on. If it is not grounding this wire then the ecm is probably not powering up and we need to figure out why.

 

So if it is not grounding that wire then the problem lies elsewhere in another wire I would guess?

Do you know the order of how voltage is directed through the Main Relay?

I feel like I am close to diagnosing this issue. The weather has not been too great lately so I have not been messing with the car.

 

I feel like if the ECU is not getting power, maybe there is a break in one of the wires from the Fuse 31, Fuse 13, or Fuse 44.

I have already checked all the fuses for these & they are all good & not blown.

& I have checked that the ground (#3 terminal for M.R.) is good.

 

 

Yes, if the ecu is not grounding that wire we have a problem else where and if its not grounding that wire the ecm is probably not getting power. You need to start by tracing that starter signal wire as it should be sending 12v to the main relay. This is what activates the main relay to power up the ecm. 5v is not enough to activate the relay. See if you are getting 12v at the fues when cranking.

 

Your thread title brought back some old memories and you could probably have added "will crank but not start" as well.

I'd recommend doing an image Google search on keywords something like this > honda ecu capacitors bad <

A few years ago I went through troubleshooting hell replacing this and that part only to find out that when opening up my wife's '93 Civic's ECU, it had a blown electrolytic capacitor on the circuit board that arched to the ECU cover.
This problem is extremely common as the electrolytic capacitorson the ECU board leak and fail due to age and/or in our situation in our Florida humid climate from moisture getting into the ECU.

You can go here to this link that some other person put out about Bad Capacitors in the Honda ECUs here -> - Someone's Blog regarding Bad Electrolytic Capacitors Honda ECUs
Since you got this car from someone else not running, the ECU might not be the right one for your car.

Hope this helps...

 

Alright thank you. My buddy & I have been thinking that somewhere in the starter wiring could be messed up. Sorry I have been busy with work & have not been messing with the car.

5V is the max voltage I was getting while attempting to crank the car. & I also remember that when doing so the starter was not even cranking over at all. Just a dead, no noise sound when trying to crank the engine.

It has been freezing out & gets dark by the time I get home from work. Hopefully soon I can get back to it.

Any other ideas besides that starter wire?

 

Thanks for the response, I will keep this in mind. But, I think I can rule out the ECU being the culprit due to the fact I am also getting the same thing when using the ECU from my EK Sedan that does in fact work.
It's weird because when we first got the car over a year ago putting a new ECU in the car got it started.
Seems like it is intermediate because once it gets started it doesn't have an issue starting unless it has sat for a few days.

 

HAve you figured out a fix?

 

Yes, sorry I have not been on here.
So this past weekend I finally got the Hatch running. My Dad & I were checking around to see if everything else was getting power. We found that the distributor was not getting
power. We tested with a screw driver in the spark plug tube touching metal & we could see there was no spark at all.
Unfortunately this cabin harness is really a mess. I found a plug that had a jumper wire in it. If I remember correctly it had two black & yellow wires, a black & white, & a small red wire.
The two wires that were jumped together were a black & yellow & the black & white. The small red wire mated up to the black & yellow wire on the shock tower plug which led to the distributor.
Not sure how my dad figured it out but he used an inline fuse from the under hood fuse box to a constant 12V
straight to the small red wire on the shock tower plug that leads into the cabin. The fuel pump primed right away & the car started instantly when I turned the key.

But, I was thinking that maybe it is the other way around & power is sent from the distributor through that black & yellow wire to something like the ignition?
It just confuses me how this car ever started before????

Basically we jumped from the under hood fuse box to that small red wire on the shock tower plug & the fuel pump primed then the car started.

What do you guys think is going on here? Because the issue at first was the main relay was not getting power & neither were the IGP1 & IGP2 at the ECU plug.

The car has been running great ever since we jumped that wire to a 12V constant.

 

You will need to give us a little more info then I think it was this wire color and this wire color if you want us to figure out what you sent power to we will need to know the exact wire colors. also I pic of the pigtail you tapped into would be helpful. You still have a problem some where. You did not fix the problem you just band-aided it. If you don't want to have other problems in the future you need to figure out what the actual problem is.

 

This sounds eerily similar to my problem. Could you perhaps post a picture of what you did to fix the problem?

 

Yeah it is deff just a band-aid type fix for now. I still think that the cabin harness is broken somewhere. I just have another swap project going on so I just needed to figure out how to get this Y8 started. I will get pictures very soon. I should have taken some yesterday because I was driving it & pulling off a wideband that was previously installed.

The pigtail I tapped into was on the driver's side shock tower plug. It was the same thick black/yellow wire that goes to the distributor & leads to the driver's side shock tower plug. That thick black/yellow wire meets at the plug to a red wire that leads into the cabin (which leads to the ignition I believe).

 

I will post pictures when I get a chance sorry, the car is my brother's & he has been driving it for a daily car so I don't always have access to it.

Best I can do is describe what I did lol. I basically measured at the distributor that I was not getting power to the thick black/yellow wire. I followed that wire to the shock tower plug on the driver's side. One side of the plug was that black/yellow which turns into a red wire leading to the ignition I believe. We used an inline fuse from a constant 12v in the underhood fuse box & splice connected it to the red wire on the side of the plug on the driver's side shock tower that leads into the cabin.

 

Hey guys I finally adopted the Hatchback from my brother so it is now mine & I will be able to work on it more.

I did try to pull the CEL this morning since it has been on. I have to recheck which ones it is throwing because one code
almost did 10 long blinks. I don't think there are any code 100s.

But, I did see that it is throwing code 20 for ELD. I wonder if that is a sign pointing towards more faulty wiring.
The CELs have been on since my brother got the car.