ecu? and...

[1813mdw]

the other night i was driving home and somehow my hood prop(which just sits in my engine bay unattatched) crossed my +and- battery terminals. the car died(duh). my battery was done for so i got a new one. i looked as thoroughly as possible for melted wires and such and cant find anything. so i looked in the fuse box and the ecu clock fuse, and injector fuse had popped. i replaced them and tried starting the car. it turns over but pops the injector fuse everytime and shows a cel and battey light. i tried to get a code off the ecu but the LED will not come on at all. i'm guessing the ecu is fried but not sure. any help?

[Bglad420]

Most likely you fried your ECU. I have one for an 89 LXi if your interested.

[1813mdw]

Most likely you fried your ECU. I have one for an 89 LXi if your interested.

thanks for the offer; but if i have to replace it i'm gonna go obd1. could the bad ecu cause the injector fuse to keep popping?


keep the ideas comin guys!!!

[lostforawhile]

thanks for the offer; but if i have to replace it i'm gonna go obd1. could the bad ecu cause the injector fuse to keep popping?


keep the ideas comin guys!!!it could but it's hard to tell what happened, probably a surge from the alternator when the battery was taken out of the circuit, I think the injector fuse is the same fuse that is field for the alternator, if you blew the voltage regulator in the alternator, which is a very good possibility, that could be the problem. if the battery plus shorted, it's also connected to the alternator output, so essentially the alternator output was shorted too

[lostforawhile]

it looks to be the same fuses that supply field current and contant voltage to the voltage regulator in the alternator, one of those fuses is ECU and I think injector

[88Accord-DX]

You probably melted some wires together around the positive lead under the fuse box. I'd pop that fuse box out & start from there.

[lostforawhile]

unplug the green connector from the alternator, disconnect and tape off the main power lead on the back of it, replace the fuses, now see if they blow. if the regulator goes, those fuses will blow.

[1813mdw]

it looks to be the same fuses that supply field current and contant voltage to the voltage regulator in the alternator, one of those fuses is ECU and I think injector

if i'm understanding this correctly; it could just be the voltreg in the alt popping the fuse that the ecu is also running off of? their still might be hope for the ecu?

[lostforawhile]

You probably melted some wires together around the positive lead under the fuse box. I'd pop that fuse box out & start from there.

if the positive and negative leads shorted together, current would only flow internally in the battery and the alternator would show a direct short to ground. I believe he has a different alternator, so it's not connected to the underhood fusebox

[lostforawhile]

if i'm understanding this correctly; it could just be the voltreg in the alt popping the fuse that the ecu is also running off of? their still might be hope for the ecu?

yes, the ecu fuse also supplies power to the voltage regulator

[1813mdw]

if the positive and negative leads shorted together, current would only flow internally in the battery and the alternator would show a direct short to ground. I believe he has a different alternator, so it's not connected to the underhood fusebox


correct. i have a 95 legend alt.

[lostforawhile]

correct. i have a 95 legend alt.

did have a 95 legend alternator , now have a crispy critter :sad2:

[1813mdw]

did have a 95 legend alternator , now have a crispy critter :sad2:

its not f*#@ing funny!



alright i guess it is:rofl:

[1813mdw]

after another inspection i found the little plastic piece that holds the plug wires together melted to the exhaust manifold heatshield. the wires don't look damaged but i wouldn't be suprised if they were from the heat. just some more info for the diagnosis

[88Accord-DX]

Sounds like you need a wiring schematic, test leads & DVM to ohm some wires out. ;)

[1813mdw]

Sounds like you need a wiring schematic, test leads & DVM to ohm some wires out. ;)

does dvm stand for dig volt meter? i have a real nice volt meter that an electrician left in the laundry room at my old apartment complex(left it for over 2 months and nobody claimed it; not stealing lol) but its not digital; i don't know how to read the needle. i've never tried using it except on speakers that i already knew the ohm rating and still couldn't figure it out. i might pick one up tomorrow if all else fails

[charliekuney]

does dvm stand for dig volt meter?

Department of Vehicle Motors

:kekeke:

[1813mdw]

thank you very much for the sarcasm, sir. :crying: jk

[1813mdw]

so today i pulled my alt and taped off the lead wire and turned the key. the battery light did not come on but the CEL did. the ECU still is not turning on. i'm gonna take the alt to get it tested tomorrow. what else could be shorted? :burn: i swear if i had insurance on my car i would burn it and and collect the claim

[1813mdw]

just went to walmart and picked up a cheap multimeter. were should i start tomorrow morn, fellas?

[lostforawhile]

so today i pulled my alt and taped off the lead wire and turned the key. the battery light did not come on but the CEL did. the ECU still is not turning on. i'm gonna take the alt to get it tested tomorrow. what else could be shorted? :burn: i swear if i had insurance on my car i would burn it and and collect the claim

did you unplug the green plug and replace the fuses? the ecu fuse is also one of the fuses for the voltage regulator so it may be blown

[ShyBoyCA6]

just went to walmart and picked up a cheap multimeter. were should i start tomorrow morn, fellas?

pick up another ECU lol :uh:

[1813mdw]

did you unplug the green plug and replace the fuses? the ecu fuse is also one of the fuses for the voltage regulator so it may be blown

the plug on the back of the alt? if so, then yes. the only fuse i replaced was the injector fuse and it popped again

[1813mdw]

pick up another ECU lol :uh:

not until i know for sure its shot for sure. it may just not be getting power

[ShyBoyCA6]

ECU light will stay on and not blink out any codes (not working).

check fuse for the ecu

[1813mdw]

ECU light will stay on and not blink out any codes (not working).

check fuse for the ecu

yeah its not coming on at all. is that the injector fuse that keeps popping? if not where is the ecu fuse?

[Dr_Snooz]

The way to track a wiring problem is to get the wiring diagram for the circuit. Then you trace the circuit through the car from the power source to ground, seeing that the voltage stays as it should. There is an excellent electrical troubleshooting manual available here (http://3geez.wiki-tv.com/Honda_service_manuals). It's for an '89, but should work fine for '88s.

Pretty much all the circuits are 12V circuits. To see if a wire has power flowing through it, you will set the multimeter to DC volts and put the red lead on the wire and the black lead to a ground source. Ground sources will be any bare (not painted) screws or bolts that attach to the engine block or body. Your multimeter will probably have a few different DC volt settings. The only difference between them is where the decimal place is on the display. To see if a wire is broken in the loom, set the multimeter to ohms (or this symbol http://www.fringebloggers.com/wp-content/uploads/2009/10/omega.gif) and put one lead on one end of the wire and the other lead on the other end. If you get a number other than zero, then the wire is not broken.

Before you do anything else, start with a good, thorough, visual inspection of the engine bay. When you short out the battery like that, you should be able to see easily where the current went. If it went to the body, then there will be a big black hole where sheet metal used to be. If it went through a wire, then the wire will be very melted and will stink like...melted wire. The fact that your plug holder melted makes me think the current went through the plug wires to ground on the engine block. Unfortunately, when you push a big load like that through something, the current can take a lot of different paths and blow out a lot of stuff. Finding it all is going to be ...interesting.

I hate to say it, but you are probably in over your head. If you were already proficient with wiring diagnosis, I would say you have a difficult task ahead of you. Trying to learn it on this job is going to be near impossible. Finding the problem is going to be hard. Fixing it could be harder. Most likely, you'll get to open a loom and look for a melted mess of wires. Then you'll get to cut out the melted mess and replace the wires. If you're lucky, this won't involve tearing out the dash or engine.

Having said that, check the injector resistor before you do anything else. If the current went through that and blew it up, then the circuit would tend to pop fuses a lot. P. 12-61 of this manual (http://honda.roadpwnage.com/manuals/pages/usdm-accord-1989-full.php) shows how to test the resistor.

You could also use the "engine won't start" troubleshooting flow charts in the same manual to see where that leads. No warranties express or implied, but it will give you something to do before taking it to the shop. The flow charts start on p. 12-10.

Finally, the hood rod grommet is only a few dollars from the dealer and the clip from a 4g works great and doesn't break. Grab one the next time you're at the junkyard.

Good luck and keep us posted.

[lostforawhile]

does the alternator lamp light up when you first turn on the key? since the alternator was directly shorted to ground, through the hood prop, it's likely something connected to it fried. most of the current would have gone from the positive battery post directly to the negative battery post through the prop, but since the alternator was creating current, all of that current would have also travelled to ground since it was connected to the positive terminal of the battery, pretty much everything in the car was for a brief second powered by the alternator and also directly shorted to ground through the hood prop, I think you have a mess on your hands.. stray currents could have traveled anywhere. let me look at the diagram and see whats on the injector fuse

[lostforawhile]

check fuse 1 and 8, it's possible you fried the ecu since it shares the same fuse as the alternator voltage regulator, unplug the ecu connector, replace the fuse that keeps blowing and see if it blows with the ecu unplugged, the other thing to consider is when the battery shorted out and the alternator shorted out, the alternator may have produced a very high voltage spike, if it did there's no telling what it fried, a shorted alternator can produce over 100 volts for a vey brief time,

[1813mdw]

check fuse 1 and 8, it's possible you fried the ecu since it shares the same fuse as the alternator voltage regulator, unplug the ecu connector, replace the fuse that keeps blowing and see if it blows with the ecu unplugged, the other thing to consider is when the battery shorted out and the alternator shorted out, the alternator may have produced a very high voltage spike, if it did there's no telling what it fried, a shorted alternator can produce over 100 volts for a vey brief time,

all fuses are checking out fine other than the injector fuse. the voltreg def is fried. got the alt tested today and its putting out 20+ volts. i've got the day off so i am pulling the driver seat and ecu next. i don't care how hard this is gonna be; i will make this car run again.

[1813mdw]

seat and ecu are out. the injector fuse is no longer popping w/ecu unplugged. if their was another problem(short) somewhere wouldn't it trip a fuse? i don't want to get another ecu just to destroy it aswell.

[lostforawhile]

i wonder if voltage found it's way to ground through the injector harness or the injector resistor? if it melted a wire in that harness, the ecu fuse would also keep blowing, if you can't find it maby someone on here will sell you a subharness from a parts car and just swap the harness, another thing to check, unplug the injectors, plufg the ecu back in and see if the fuse blows then, the high voltage might have even caused an injector coil to short

[Dr_Snooz]

Have you checked the injector resistor?

[1813mdw]

Have you checked the injector resistor?

when i pulled the injector resistor i tested the black pinout to the 4 red ones and they each read 6.5ohm. on top of my car troubles my computer crashed i'm at the library; and not one single jy around here has the pjo-668 ecu i need. when it rains it pours:beat:

[2drSE-i]

when i pulled the injector resistor i tested the black pinout to the 4 red ones and they each read 6.5ohm. on top of my car troubles my computer crashed i'm at the library; and not one single jy around here has the pjo-668 ecu i need. when it rains it pours:beat:

Any 88-89 lxi or sei ecu will work, not that I'm sure thats your problem.

[1813mdw]

Any 88-89 lxi or sei ecu will work, not that I'm sure thats your problem.

even the automatics? i'm not sure it is my problem now either; my battery keeps dying even w/ecu unplugged. i'm pulling the dash tomorrow and cutting open looms. after a "sniff test" something back there is def burnt.

[Pico]

automatic too, I kept my a/t ecu after I did my 5 speed swap

[lostforawhile]

your best bet may be to have someone on here pull you a harness, it takes some time, but everything will simply attach back like factory, there is no telling what got fried

[Dr_Snooz]

Gawd, this is such a drag. Sorry you have this mess to clean up. Hope you get it all sorted out. I think it's worth the $13 the dealer wants for the clips to hold the prop rod.

[1813mdw]

nothing in the looms under dash is burnt/melted. i found that the injector fuse only pops if the white harness is plugged into the ecu. so, my plan is to buy a ton of fuses and pull pinout by pinout until i get the fuse to stop popping. i've got the color codes for them so hopefully this will help me narrow it down.

[88Accord-DX]

Fuses are cheap, but you can put some thin wires into the suspected circuit up out of the fuse block & use jumper leads in series on your DVM set on amps..... (lowest reading) With a good testing on each circuit in resistance measurements, you typically don't need to remove pins out of the terminals to isolate it.. I personally use test leads that can accept a back probing needle to test circuits on each side on both connectors ends. (long leads)

I like using this to narrow it down.

http://ecx.images-amazon.com/images/I/21mz4Zd-OzL.jpg

[lostforawhile]

when you say injector fuse, do you mean fuse #1? I can't remember but doesn't the ECU tell the main relay to switch on? fuse 1 is Main relay, alternator, fan controller timer, warning display, speed sensor amplifier, electronic air control valve. you caused enough of a surge in the alternator to blow the regulator, I would be checking the alternator harness, it's possible some wires melted together, if the wire going to the regulator from fuse 1 is shorted, every time the main relay powers up, the fuse will blow. let me go back to my diagams

[lostforawhile]

you said the white connector at the ECU? this is gound for the fuel injection relay, the computer switches on gound, this causes the relay to close, switching power through the relay to the injector resistor box, this always has power when the ignition is switched on, it splits the power into four resistors, one for each injector, the computer switches the injector grounds to contol the injectors. the injectors also recieve power through fuse 1, you said something about an injector wire melted? the computer does control the main relay though, so when it tells the relay to turn on, something off of fuse 1, the alternator or an injector wire is shorted and the fuse blows

[1813mdw]

when you say injector fuse, do you mean fuse #1? I can't remember but doesn't the ECU tell the main relay to switch on? fuse 1 is Main relay, alternator, fan controller timer, warning display, speed sensor amplifier, electronic air control valve. you caused enough of a surge in the alternator to blow the regulator, I would be checking the alternator harness, it's possible some wires melted together, if the wire going to the regulator from fuse 1 is shorted, every time the main relay powers up, the fuse will blow. let me go back to my diagams


the injector fuse is in the fusebox in the engine bay. they are all labeled not numbered. i'm going to pull apart the alt harness tomorrow and check. while hooking up my new alt yesterday i found a random wire w/ a connector dangling from the middle of the alt harness. it is white and red; does anyone know what it goes to?

[1813mdw]

you said the white connector at the ECU? this is gound for the fuel injection relay, the computer switches on gound, this causes the relay to close, switching power through the relay to the injector resistor box, this always has power when the ignition is switched on, it splits the power into four resistors, one for each injector, the computer switches the injector grounds to contol the injectors. the injectors also recieve power through fuse 1, you said something about an injector wire melted? the computer does control the main relay though, so when it tells the relay to turn on, something off of fuse 1, the alternator or an injector wire is shorted and the fuse blows


i'm yet to find any melted wires; the piece of plastic that holds the sparkplug wires melted. and i found that the burnt smell behind the dash was coming from my cd player. my next step (affer continuing to ripping apart looms)is gonna be to get an ecu and hook it up and see what happens. hopefully the car starts up; but i always expect the worse lately in life. things just havent been going good for me lately:banghead: i know i'm prob drivin some of you crazy w/ my ?'s ; but i can't thank you guys enough for your help

[lostforawhile]

i'm yet to find any melted wires; the piece of plastic that holds the sparkplug wires melted. and i found that the burnt smell behind the dash was coming from my cd player. my next step (affer continuing to ripping apart looms)is gonna be to get an ecu and hook it up and see what happens. hopefully the car starts up; but i always expect the worse lately in life. things just havent been going good for me lately:banghead: i know i'm prob drivin some of you crazy w/ my ?'s ; but i can't thank you guys enough for your help

check the wires coming from the alternator loom, this is a likely place to have a melted wire as the regulator burned out in the mess. when you plug in that white wire, the ECU tells the main relay to switch on, if anything connected to the main relay has a short, it will blow the appropriate fuse, in your case the injector fuse is blowing, if the ecu was bad, it would be blowing a different fuse, that fuse that is blowing is also supplying power to the voltage regulator

[1813mdw]

check the wires coming from the alternator loom, this is a likely place to have a melted wire as the regulator burned out in the mess. when you plug in that white wire, the ECU tells the main relay to switch on, if anything connected to the main relay has a short, it will blow the appropriate fuse, in your case the injector fuse is blowing, if the ecu was bad, it would be blowing a different fuse, that fuse that is blowing is also supplying power to the voltage regulator

its not the white wire; its the white "harness?" that plugs into the ecu. their is one big white one and two smaller black ones, the fuse only pops when the big white harness is hooked up and even then the ecu will not turn on. this makes me think that something inside the ecu is shorted out. phrenology is sending me an ecu this weekend so i still have time to go through looms and such. do you know where the white wire w/red stripe that comes out of the alt loom is supposed to hook up? it comes out under the intake manifold and has a connector on the end of it but i can't find where its supposed to go

[Pico]

what kind of connector is on that loose wire, is a plug or a eyelet?

[1813mdw]

what kind of connector is on that loose wire, is a plug or a eyelet?

sort of a plug. the guy i bought the car off of said it goes to the oil sending unit.

[1813mdw]

the ecu was bad; hooked up a new(used) one today. the injector fuse is no longer popping but the car will still not start. i am getting spark at the plug wires. i'm still getting a CEL, but still no code from the ecu. is there a sensor i could have fried that would cause this? i could not hear the fuel pump kicking on but, it was raining pretty hard and i don't think i'd been able to hear it either way





after some searching i'm gonna check the fuel pump, then the main relay. ideas and are still welcome, though. still don't know what to make off the CEL w/no code

[88Accord-DX]

I would check to make sure you have a good ground to the ECU.. (in the connector pinout) Then load test the circuit to make sure it can hold a load of bullets. (current) :gun:

[lostforawhile]

:gun:I would check to make sure you have a good ground to the ECU.. (in the connector pinout) Then load test it to make sure it can hold a load of bullets.

with what fried with the battery shorting, I think he has worse problems then that, when the battery went the voltage regulator went out on the alternator and the system voltage spiked to over 20 volts, plus all kinds of strange current paths could have developed. when the alternato was tested it was putting out over 20 volts. when the battery saw a direct short to ground , so did the alternator

[Dr_Snooz]

Are there any Florida members who could drive over and lend a hand here?

[88Accord-DX]

with what fried with the battery shorting, I think he has worse problems then that, when the battery went the voltage regulator went out on the alternator and the system voltage spiked to over 20 volts, plus all kinds of strange current paths could have developed. when the alternato was tested it was putting out over 20 volts. when the battery saw a direct short to ground , so did the alternator

I'm going off his last post at #50, with the way the car is acting. He has replaced the ECU, got spark, fuse is not popping. (my memory/date base recalls a ground being a problem on similar concerns. )

[1813mdw]

its alive!!!!!! when i went to check the main relay i found it unplugged. i had unplugged every thing down there trying to follow wires and somehow missed that one. i'm picking up an alternator today an re-looming everything i tore apart. also, the dash and front seats are going back in. should be able to drive it to work on sunday. in all, it was the ecu, alternator, battery, and cd player that took a hit. I WANT TO THANK ALL OF YOU THAT HELPED ME TROUBLESHOOT THIS, YOU HAVE NO IDEA HOW MUCH IT HELPED. :bow::bow:

[Dr_Snooz]

Congratulations! Your success owes much to your determination and resourcefulness. You might find some other things that don't quite work the way they did before, but it looks like you're through the worst of it. Very well done!

[lostforawhile]

its alive!!!!!! when i went to check the main relay i found it unplugged. i had unplugged every thing down there trying to follow wires and somehow missed that one. i'm picking up an alternator today an re-looming everything i tore apart. also, the dash and front seats are going back in. should be able to drive it to work on sunday. in all, it was the ecu, alternator, battery, and cd player that took a hit. I WANT TO THANK ALL OF YOU THAT HELPED ME TROUBLESHOOT THIS, YOU HAVE NO IDEA HOW MUCH IT HELPED. :bow::bow:

you didn't slap a big handprint into your forhead did you? I hate when I miss something simple,tear everything apart and :uh: I'm glad you didn't give up and got it fixed

[MessyHonda]

feels good for easy fixes

[1813mdw]

you didn't slap a big handprint into your forhead did you? I hate when I miss something simple,tear everything apart and :uh: I'm glad you didn't give up and got it fixed

no :uh: lol. i just got real giddy when i found it unplugged; thinking it might start finally

[1813mdw]

Congratulations! Your success owes much to your determination and resourcefulness. You might find some other things that don't quite work the way they did before, but it looks like you're through the worst of it. Very well done!

yeah i was expecting little things here and there. it runs and all my lights/turn signals work so i'll be good for a min while i work out any other problems i come across

[Vanilla Sky]

Man, I totally forgot to return your call when I got my new phone. I hadn't added you to my contacts yet, so it didn't transfer over. Send me a text some time if you have stuff like this happen again and need an ear instead of a keyboard.

[lostforawhile]

I was going to type this up, but I found it already explained on the web, what happened when the battery shorted, was the regulator saw a dead battery and went to full voltage, with no battery to balance the load the voltage spiked out of control, frying the alternator and the ecu, and other things, here's a good explanation, this is why you never disconnect the battery while it's running.
Testing an Alternator Without Blowing it Sky High

8

Nothing makes me crazier than reading advice that tells readers to disconnect a battery cable while a car is running to see if the alternator is any good. It’s not only bad advice, but could cost you big time in fried computers.

Here’s why: To generate power, you pass a coil of wire across a magnet. It’s basic physics #101. In an alternator, they turn things around. They rotate a magnet past a stationary coil of wire. The key here is that the magnet is an ELECTO magnetic. That’s right folks, you need a good battery to provide the power to make the electro magnet work in the first place. An alternator cannot make power if your battery is dead. This is why you cannot charge a dead battery with the car’s alternator. No 12 volts in=No 13.5 volts out. Back to the story. So when you start your car, the voltage regulator takes a look at battery voltage. If it’s at 12.7 volts, the regulator determines that the battery is in good shape and doesn’t need charging. But once you turn on headlights, a defroster grid, or a blower motor, you begin sucking power out of the battery. The regulator sees that battery drain and sends battery voltage into the “rotor” of the alternator. The rotor is the rotating electro-magnet. The “stator” is a coil of wire that’s stationary and is where the electricity is produced.

If you disconnect a battery cable while the car is running, the regulator sees total battery drain and immediately commands the alternator to run at maximum output. In effect, the alternator is now running wild. In this state, it can put out upwards of 40 volts. That’s enough voltage to fry your powertrain computer, your ABS computer, your radio, and every other computer in your car. It’s also enough to fry the guts of the alternator itself.

Are you getting the idea here? That it's not a good idea to send the alternator into ‘full tilt?”

So, how DO you test an alternator? Simple. Get a volt meter and attach it to the battery. Make sure you have at least 12.2 volts before you start the test. If the battery reads less than 12 volts, you will never be able to test the alternator. If the battery voltage checks out, start the vehicle and rev it up to about 2,000 RPM and turn on the headlights. You should see voltage go to at least 13 volts. If you vary the RPMs, you should see the voltage fluctuate between 13 and 14.5. That’s the sign of a good alternator—volts wise.

As for an amperage output test, that’s a little more difficult. You need special equipment for that. That’s where an auto parts store comes in handy. They usually test alternators for free.