alextech

I have a honda civic 93 hatchback automatic, mostly when it is humid outside the car will take a long time to turn on. I have researched this problem frequently and here is what I have done:
Changed the fuel filter (really dirty)
Changed fuel pump
Changed main relay
Cleaned thermostat ground
Changed the ECU.

Sometimes I would get barometric sensor code 13. I bought this ECU on ebay, and I talked to him about it and said that I could have an electrical issue. He says he tests his ECUs and makes sure they start up and work. Could it possibly be the fuse box? The reason why I think it might be the fuse box is because previously I had a problem with the driver side headlight. Sometimes the headlight would not want to turn on with no apparent explanation. Also this headlight ground cable goes to a ground box and I have noticed that ground box would make a spark sometimes when I touched the chassis. But anyways I ended up using the passenger headlight cable to turn the other headlight on. I dont know if this has anything to do with this problem, just so you know.

alextech

I found an interesting thread that may help me diagnose my problem. Ima try to see if I can fix the problem and post back to see what I find. Here is the link:

https://honda-tech.com/forums/honda-...issue-2815857/

alextech

According to the thread, B1 is supposed to be ground on ECU correct? I checked if my ECU is getting ground on B1 and it is not getting ground. A23, A24, A25 is getting ground. I have checked if its getting ground with powerprobe 4 tool. Also on the MAP sensor connector, I am getting about 3v, Ground, and 5v. I tried checking for voltage drop using LoadPro tool and loaded it and dropped to 0, meaning it was not activated but no short indicated. But, after loading it, I connected it to the MAP sensor and fuel primed. Its been 2 days since I couldnt turn the car on and was thinking my ECU fried again. Can anybody help on what I have to do next? Do I cut the B1 cable and give it ground?

alextech

bump... does anyone know where yellow/black wire goes to from ECU?

mk378

B1 is power. Yellow/black wires are almost always power. B2 is a ground.

It is quite possible your used replacement ECU is also bad, with the same "slow to boot" problem as the original one.

alextech

Ok, when I said B1 is not getting ground, I meant is not getting anything at all, no positive no negative. Is this normal? So, just maybe the ECU can also be bad, I will see if he wants to trade it or not. Also, I read in another thread that disconnecting the MAP sensor can somehow preprogram the ECU. Also the yellow/black cable could be going to the fuel pump, according to this thread:

https://honda-tech.com/forums/honda-...-92-a-2640218/

On his MAP sensor connector, the white cable is getting about 0.3 v. On mines is different, cant remember if it was white, but there is only 1 ground and the other 2 cables is 3v or 5v. Im going to try to replace the ECU again, but I find it strange it does the same thing.

alextech

I changed the ECU again, and it did the exact same thing. It takes a long time to start up. Any help? Also, fuel pump primes immediatly after MAP sensor is disconnected. Why does this happen? Another question, Im assuming my ECU is OBD1 correct? Because if it was obd0 the barometric sensor would be near the blower, but its not its on the ecu, I would assume.


*Update
Also on MAP sensor connector the cable Pink/White is about 4v, Green/Yellow is 5v, Middle is ground. Now here is the interesting part, The Pink/White (D17) cable is about 3v on the ECU, and that cable is right next to the Red/Yellow cable which seems to belong to the left headlight I was talking about in the beginning. But, on the diagram it says its for the Intake Air Temp sensor.

alextech

bump... any recommendations on where I can take it to diagnose this problem or have any idea what it is?

alextech

I found something weird about my car, today the only main thing that I did was upgrade my speakers. While I was doing that the CEL was off but after a while it decided to turn the CEL on. But the strange thing that I found out was that when I take fuse 15 off the car starts beeping when I have the door open. Thats weird shouldnt it be the other way around? I now notice the car is even worse, the car will shut off by itself when it is on! Is probably normal to beep. Then, the next thing I did check is pin A25 and B1 on the ECU, and basically it seems to struggle getting ground/resistance, the resistance reads 310 ohms and cuts of each second and on the main relay terminal 3, it reads 11 ohms. And if the fuel does prime, A25 and B1 will stay at 12v. Could it be the ECU again? I rather buy the ECU new, rather than used if it really is that.

alextech

Anybody have an idea? I found something else strange, my stereo doesnt save the settings. I been told the yellow and red wire maybe switched. Buy I checked and I was told the yellow wire has to have 12v constant and I checked and its doing something related to my main relay. Its getting ground instead and it cuts of each second. And I know they are not switched.

alextech

bump. Im going to take a wild guess that it could be my ignition switch cylinder?

alextech

Ok another update, the cables that go to the thermostat housing are getting 4v without touching thermostat. Is this normal? When I leave it on the thermostat it measures 0v. Anybody know the problem? According to this thread its supposed to be 12v on A25 and B1 and on mine its not with key off.
https://honda-tech.com/forums/tech-m...tions-3236903/

alextech

I have too much posts, another update. I had someone checkout my car and they told me the main relay is not getting ground from the ecu. Anybody have an idea whats going on?

tony_2018

dude, please download the fsm and follow the diagnosing charts for each component and wires and connectors

alextech

I downloaded the FSM manual and was checking the connection of the main relay and the ECU and when I got to the last step. I had to check A7 and A23 and got 10v and I dont know if you know about loadpro, I was testing it with my loadpro and when I loaded it the fuel pump started running and the voltage dropped to 2v. If it is the ecu im going to put a reman. ecu.

mk378

The ECU pulls A7 to ground to start the fuel pump. The fuel pump starting when you grounded A7 shows that the main relay is OK.

When the ECU does not boot up, the CEL stays on and A7 does not pull to ground. You need to test all the power and ground wires on the ECU to confirm that they are indeed powered and grounded. If that is OK, the ECU is bad.

alextech

I can confirm that I have fixed the problem, I replaced the ECU with a completly remanufactured ECU. The fuel primed instantly. I think I learned my lesson on not buying used ECUs on these types of civics.