pschum

Hey Ron,

I was able to get back to the Honda on Sunday. I pulled out the ECU and opened it up to see if there was any visable damage.

Man it looked like it flamed a little there was a burn mark on the cover and a hole melted in the unit. I should have taken a picture to show you.

It requires a 37820P28A51 ECU (Verified by the number on the existing one)so we're going order it.

Any good sources you could recommend?

Thanks again for all your help.

Pete

Former User

One concern is that a short in a ECU wire or sensor destroyed the ECU. If so, this potential short could also destroy your replacement ECU. Post several clear front/back pictures of your bad ECU. If you are lucky, someone may be able to look at the burned areas and tell you specific ECU wires to test for a short.

pschum

Ron,
Thanks. Here's the pictures I took. It's that brownish round capacitor that fried.

Former User

Wow. That's the worst ECU blow out that I've seen.

Bump for anyone who may be able to identify a possible source for this ECU failure.

Pete, you may want to PM member 94EG8. He may be able to give you some input.

HondaWrench

This is a rare and interesting, thanks for the images, Pete. This looks like a ground fault, or a ground short, not actually a problem with the ECU, I believe. Some wire, somewhere in the car had decided to grab a hold of 12V and then rush the 12V+ of pure power, with no fuse protection, into what we call the ECU ground. Another words, if you put the wrong polarity to the ECU something's going to fry.

The solution to this problem is first check the harness while the harness is still connected to the ECU (check pin B1 yellow/black) and make sure it's ground, If not, cut that wire and then run a separate ground wire there - eventually going into into the ECU. Second, check the harness one at a time (pins A23, A24, A25 this is all based on the link http://www.phearable.net/tech/wiring...schematics.gif Ron J posted) and make sure it is ground, If not, cut those wires and run another ground wire there. This is because the ECU typically has many grounds. Do that before you plug in your new ECU, otherwise you'll fry your new ECU. Also, it would be wise to check all the inputs pins into the ECU and make sure it isn't 12V+ where it isn't suppose to be, or ground where it isn't suppose to. If you are unfamiliar with this, alternatively, you might want to try tear the car apart and find that short and yank it out. This will leave no possibility that the short could do more damage.

Secondly, the ECU looks like it's salvageable because none of the other components are affected, except for the traces. The giant diode (the fat black grenade looking thingy) had protected the ECU. In some other cars, other than Honda, you could be facing all sorts of damage and expenses. This is one reason I stay with Honda or Toyota.

That's all the advice I give at this point, they may or may not be accurate because I'm not there to probe around. Other than that, if you really want to help you could report back what voltages you did find on pins B1, A23, A24, A25 to ground, as mentioned above. They should be zero Volts. If they are not zero Volts, use your handy skills to turn them zero Volts. Probing these pins is part of the process of hooking up a new ECU and will also help others solve the puzzle.

pschum

Thanks Ron and HondaWrench,

I will try to check all this out and will do so before I plug in the new ECU.

I did notice that a battery sized cable that grounds the engine to the frame looked like it was some what burned almost as if it was smoked also had sort of a green build up on it. I took it off and cleaned it up but the wires just don't look good. Not sure if that was and issue.

I have a meter as I wrote Ron but I'm still not sure on how to check these ground issues or from the pins on the plugs If you or Ron can show me a picture then I can get it (Sorry for being so stupid on this guys) and I do really want to again thank everyone for helping out.

Pete

HondaWrench

Usually, people would complain that acid spills (which eventually leads to shorts) will fry all kinds of components on the car. After the cleaning, you may have eliminated the shorts, which is great, but might be confusing when your probe results say that there are no shorts.

You might want to put the red probe of the multimeter and put it in the cigarette lighter socket, (see image) the center part that's deep inside that hole. Turn on the ignition so you have power to the lighter. Second put the black probe to a metal ground part of the car, a bolt or something, or the metal outside ring on the cigarette lighter. It should read about 12V. Make sure the harness is connected to the ECU. Next, while keeping the red probe steady and firm on the cigarette lighter socket, put the black probe on the metal strip (pins) part I've pointed on with the arrows (for example B1, etc.) These are the ECU ground. Looks like there are lots of them I've missed earlier. It should read about 12V. If not then you've found the problem.

Next, while continuing to keep the red probe steady and firm on the cigarette lighter socket, probe B2. It should read 12V. Lift up the black probe and then put it on A25. Write down the voltage down. This will be useful for others who understand what the voltages mean. Keep on probing all the other pins (A26, A24, A23) that I've pointed on with the arrow until all of them are probed. What you are looking for is one that did not read 12V. If it doesn't read about 12V then the wiring that leads to that pin is damage. To fix it, you might need to cut that wire and bolt it to the frame of the car or where it normally bolts to.

A word of caution: When probing the metal pins, don't allow the probe to touch other pins next to it. Just touch the pins you want. Hold your breath, to keep your hands from shaking. A slip up could mean a frying death to other components.



All the pins I mention here are ground, are reference to the diagram Ron Posted. It's only accurate as the diagram. So, please double check my work.

pschum

Thanks HondaWrench,

Great pic's that really helps me. Love how you drew the meter wires in too. Is it possible to check these same plugs without the ECU? It may have already been sent off to IL for repair.

Thanks,

Pete

HondaWrench

Yes, that's fine. From the visual appearance of the burnt board it looks like the only short is the yellow/black wire (pin B1.) I wanted you plug it into the ECU because that tells a lot more. But that isn't necessary.

For your reference there may be 13 ground pins altogether, you might want to check them all, if you get the chance. Here are the pins.

A23 power ground
A24 power ground
A25 power ground
A26 sensor ground

B1 power ground
B2 sensor ground
B12 sensor ground
B13 sensor ground
B14 sensor ground
B15 sensor ground
B16 sensor ground

D21 sensor ground
D22 sensor ground

Beware that when the ECU is disconnected, some pins (such as the sensor ground) may no longer be ground. That is when an ammeter comes in to play. Your meter can measure amps but they're kinda too low for this.

pschum

Well, I checked all like RonJ@HT and HondaWrench suggested and ordered the ECU from a source suggested here on this site by another guy.

When I was checking ground as Ron and HondaWrench wrote don't cross touch any other pins or other crap could short

So I put the new ECU in and had my fingers crossed as I turned the key to start. Nothing! man I was bummed... I'd worked on this thing for so long and I felt defeated...

Then I remembered what you guy wrote and thought I should check the fuses again since I had that slight spark when checking the pins...
Sure enough, the ECU 15 Amp fuse had blown! I changed it said a prayer and turned the starter key and BAMB! It started on the first turn of the key

I owe it all to you guys... Thank you Ron for guiding me through this and thank you HondaWrench for helping me with this as well you and others who also offered suggestions were great. It sort of restores my faith in humanity that so many folks were willing to take the time and help. Thank you all.

Pete

pschum

Well, here I am again. It's only been a few weeks of ok running with the new ECU.

The car just stoped running. ECU still looks good, it's getting fuel but NO Spark.... Not sure what to check now all fuses are ok.

Any ideas where to start

Thank you,

Pete

Former User

Any CEL codes?

Remove the distributor cap and the 15A hood fuse 31 (ECU/PGMFI). Have a buddy crank the engine while you check whether the rotor turns. If so, the timing belt did not snap.

Now also remove the rotor and inner cover. Check whether there is battery voltage on the Blk/Yel wire attached to the igniter unit. If so, remove the coil and resistance test it and take the igniter unit for testing at an auto parts store.

pschum

Thanks Ron.

No CEL codes that I noticed after I turn the key on the CEL goes out.

One thing I didn't wriet is that a 15 amp fuse to I think the lights was blown,
I replaced it but that didn't help. All others are good.

Also the car had overheated some that my sons girlfriend stopped let it cool down and then put antifreez in it then it ran okay until it just stopped.

The rotor is turning as I took the cap off to clean inside and had to crank it to align the screw that holds the rotor. The 15Amp ECU hood fuse is okay too.

I'll check those wires for voltage. Are the coil and igniter separate parts that just come out?

Thanks Ron,

Pete

Former User

Does your distributor have an inner cover?

Yes, they are separate and just come out:

pschum

Got it thank Ron.

Pete

pschum

Ron,

Just want to be sure on the spark plug wires can you tell me looking at the engine what the plug numbers are which one is #1,2,3 & 4. I marked them to be sure I put them back on in the same order but I just want to be sure.

Let's say from where the distributer is the closest plug is ?

I don't know why but I feel like I'm on a quest to get this thing running at least for more than a week since we just put the new ECU in.

Thanks again for continuing to help me on this quest ,

Pete

pschum

Hey Ron,

Yes the distributer has an inner cover.

I checked the Black/Yellow wire and I do get 12 Volts when the key is turned to position II.

I checked the coil with my multimeter and got 0.8- 0.9ohms at terminals A & B

At the secondary winding terminal from A I get 10.41 Not sure if I'm checking it right as the info. you sent me said this should be 13,200-19,800 ohms.

I took both to a local auto parts store and they couldn't test it as they didn't have the know how or equipment. I'll try another.

Is there a test I can do on the igniter?

Thanks Ron,

Pete

Former User

Your test results indicate that the coil is bad. The second test was 10.4 kOhms but should have been 13.2-19.8 kOhms. Start by replacing the coil.

Call additional auto parts stores in hopes of finding one that will test the igniter unit for you.

pschum

Okay Ron thanks.

Pete

ruffneck460

Sorry to resurrect this old thread but I have a problem closely resembling this one, My vehicle (93 civic ex 1.6l) would not start after in running/driving it awhile then stopping and maybe go in store or something come out few minutes later no start let set a little longer then it would start after cranking it awhile. then about a week ago while driving it died and would not start at all, I figured it was fuel pump dead, since this vehicle has 229,000 miles. But I later discovered the ECU fuse 15 amp in underhood box was blown replaced and the vehicle started right up ( I did replace fuel pump BTW) I then drove it about a mile and it died again same fuse blown replaced it and it blew again as soon as key turned on...towed it home again...
Is this the main relay or should I look elsewhere..I have looked at a number of threads on here and the relay seems to be the main problem but could find none that mentioned the ECU fuse glowing...Any help would be appreciated! sorry new on here so not able to start a new thread yet!

todajas

Hi Ron,

aplease advise for below,

ECU- P30 (civic 92, B16a)

B1 - 5v
B2 - 5v
B12 - 11V
B13 - 12v
B14 - 12v
B15 - 5v
B16 - 12v

is it normal?

Former User

How and why are you doing these voltage tests? Are any connectors unplugged? What are you using for ground?

B2 is a ground wire, and B12-B16 are wires for the distributor sensors. You would normally make resistance measurements for these.

todajas

Former User

If you jump the service connector, does the CEL blink any codes?

Does the fuel pump prime?

Is there spark at the plugs?

g3tt1n1t1n

im having this same issue. i replaced my fuel pump and it primed fine for like a week then it primes when it wants i think this is my main relay but i dnt know forsure it looks bad but we will see soon as the relay gets here. if u could also walk me through this it would be greatly appreciated