midwesta

I have a 1992 DX hatchback with a jdm itr motor w/ gsr head etc..

p72-a01 ECU

My 15amp (blue) ECU fuse in the underhood fuse box keeps blowing. It would do it sometimes before, but then it would stop. Now it is doing it within 5-10 seconds of turning the motor on.

The car was running fine for 1000 kilometers. Then we pulled the ecu out and we were going to tune it with wideband o2 and uberdata. My friend plugged his uberdata cable from the chip spot on the ecu to his emulator and the cable from the chip to the emulator, one of the wires got REALLY hot and melted the cable. We then pulled the chip with cable out, and cut the jumper cable as to run the ecu as stock. We plugged the ecu back in and the car ran fine, we left the ecu on the floor and my brother held it between his feet on the ride home. Which was about 30 miles. So the car ran fine again and didnt blow a fuse for the 30 miles home. Then the next day i washed the car and put the ecu back up in the kickpanel. I then drove the car 10 miles and it died. ECU fuse blew. I pushed the car into a parking lot and replaced the fuse. turned on the car, and it blew within 10 seconds. I went home, got the ecu pinouts and everything from the ecu thread and went back and took a look, i replaced the fuse again, and turned the key to on. the fuse did not blow. turned the car on, and the fuse blows in 5-10 seconds. The only codes i was throwing before was Knock sensor (dont have the wires hooked up) and the primary o2 heater code (could be because i didnt screw the o2 back in all the way after trying to tune it)

and i am pretty sure it is not the ecu itself, because this was happening when i had an LS motor in the car temporarily while i was building the jdm itr. And the same fuse was blowing. I know its gotta be some wiring by the ecu because it happens off and on when the ecu is moved...

what could be causing this?? does anyone have any ideas.

help because my car is stranded right now in a parking lot of a business place. I am gonna go back with a diff ecu and a voltmeter to test some of the volts.

another question, with the ecu unplugged and using the FF squad wiring diagrams will i be able to probe the 3 ecu plugs and get the voltages still???

TIA

skunk2powered

i had the same exact problem, recheck all your wires in your engine bay, especially the ones that you cut or rewired, make sure the wires arnt grounding off to any other wires or any type of metal, also if you have an aftermarket header, you might have had to leangthen the o2 sensor wires to reach the headers, so check the wires so that they arnt grounding off on the headers. my ecu fuse kept blowing because i extended the wires for the o2 sensor and the wires touched the headers and melted leaving the wire exposed, and it grounded off the the headers. good luck

midwesta

thanks for that info. that could help a lot. cause my o2 CEL censor was going off. hmm.

midwesta

HELP!!!

CivicSiRX

its definetly a short in the wire somewhere. on my bros ek hatch, he just threw in a greddy turbo kit, and all of a sudden the fuel fuse kept blowing. couldnt figure it out for hte life of us, then found out its was one of the wires from the harness underneathe the intake manifold that was rubbin the chassis. look everywhere. good luck.

midwesta

the thing is, it was happening with my old motor, which was a different harness. i am gonna try unplugging the o2 sensor tomorrow, maybe thats it. who knows.

more IDEAS!!

MiKeAhOwSkI

I know when my car did this, it was because I did a poor electrical tape job on my splices for the V-afc harness and they were grounding out on the chassis.

try a different ECU if possible.. or check anywhere you have tapped into the harness if you did.

another time it did this is when my 02 sensor wires came unsoldered and grounded out on the steering rack/mount. usually it is a wire grounding out.

midwesta

Okay its blowing the 15amp fuse, which is a pretty big fuse.

so i am going through all of the things in line with the plug and this picture.

I have BOLDED everything i think it could be, any other ideas, please post them up.



KEY:
(Wire color), (Function/Description (if need be)), (Voltage Value (DC Volts Unless otherwise specified)
V = Volts
Wht = White
Blk = Black
Grn = Green
Yel = Yellow
Brn = Brown
Blu = Blue
Org = Orange

KOEO = Key on; Engine OFF
KOER = Key on; Engine Running

OBD1
A1-INJ1 INJ1 Brown, Battery Voltage with KOEO
A2-INJ4 INJ4 Yellow, Battery Voltage with KOEO
A3-INJ2 INJ2 Red, Battery Voltage with KOEO
A4-VTS VTEC solenoid GRN/YEL, N/a
A5-INJ3 INJ3 Blue, Battery Voltage with KOEO
A6-PO2SHTC O2 sensor (heating element) Org/Wht, Battery Voltage with KOEO
A7-FLR1 fuel pump Grn/BLK, Battery Voltage with KOEO
A8-empty A7 and A8 have the same circurt, so they can be the same
A9-IACV IAC valve Blk/Blu, About 10v KOEO on Warm engine
A10-empty
A11- This is EGR Control Solenoid Valve (if the ECU has) Red, N/A
A12-FANC engine coolant temp switch Blu/red, N/A
A13-MIL MIL (check engine light) Blu/wht, N/A
A14-empty
A15-ACC (a/c compressor clutch) Red/Blu, N/A
A16-ALT C alternator Wht/Grn, N/A
A17-IAB IAB Solenoid Pink, N/A
A18- Org/Red, Transmission Control Module (A/T), N/A
A19- White, Intake control solenoid, Battery Voltage with KOEO
A20-PCS EVAP purge control solenoid Red/Grn, N/a
A21-ICM ICM Yel/Grn, Ignition Control Module (ICM) Output signal, About 10V KOEO
A22- *per Sander* Ignitor same as A21
A23-PG1 ground Black, Power ground, less than 1V
A24-PG2 ground same as A23
A25-IGP2 to main relay and to gound for o Yel/blk, Battery positive from Main relay, Battery Voltage with KOEO
A26-LG1 gound Blk/red, less than 1V

B1-IGP2 to pin A25 Yel/Blk, Battery positive from Main relay, Battery Voltage with KOEO
B2-LG2 ground to shields for CYP & TDC Brown/Blk, Less than 1V
B3- Orange, upshift/downshift comparative input, N/A
B4- Pink, upshift/downshift comparative input, N/A
B5-ACS a/c switch Blu/Blk, A/c input, About 5V with KOEO & A/C off; less than 1V KOER with A/C & blower on
B6-empty
B7-Light green, Park/Neutral switch (A/T), Less than 1V in Park or Neutral with KOEO; 5V in Park or neutral with KOER; Battery voltage in all other positions
B8-PSPSW PSP switch Red/Green, Power steering oil pressure switch, 0V KOEO; Battery Voltage KOER While slowly turning steering wheel
B9-STARTER SIGNAL starter signal Blue/red, Battery Voltage in the START position (clutch depressed on M/T models)
B10-VSS vehicle speed sensor Orange, Pulses 0-12V while turning the left front wheel
B11-CYP P CYP -P Orange, CYP sensor input, N/A
B12-CYP M CYP -M White, CYP sensor signal, N/A
B13-TDC P TDC -P Org/Blue, TDC sensor input, N/A
B14-TDC M TDC -M Wht/Blue, TDC sensor signal, N/A
B15-CKP P CKP -P Blu/Green, CKP Sensor input, N/A
B16-CKP M CKP -M Blu/yel, CKP Sensor signal, N/A

D1-VBU Back Up Power Wht/Yel, Battery positive From battery through Fuse Box, Battery Voltage at ALL times
D2-BKSW brake switch Grn/wht, Battery voltage at all times
D3-KS Knock Sensor Red/Blue, N/A
D4-SCS service check connector Brown/Wht, About 5V (M/T); About 11V (A/T)
D5-empty
D6-VTM VTEC pressure switch Light Blue, N/A
D7-TXD/RXD (data link connector) Light Green/Red, N/A
D8-empty
D9-ALT F alternator Wht/Red, Alternator Charging Signal, About 4.5V KOEO; Decreases under Electrical load (Headlights & rear defogger on) At warm idle
D10-ELD electric load detector input Grn/Blk, N/A
D11-TPS TPS Signal Red/Blk, About 0.5V KOEO with throttle fully closed; About 4.5V KOEO with throttle fully open
D12- Wht/Blk, EGR Valve Lift sensor, About 1.2V KOEO
D13-ECT ECT sensor input Yel/Blu, About 5V KOEO (varies with temperature)
D14-PHO2S O2 sensor White, heated 02 sensor Signal, 0.4-0.5V when ignition is turned on; drops to less than 0.1V within 2 minutes
D15-IAT IAT sensor Red/Yel, Intake Air Temperature signal, .05-4.5V KOEO(Varies with temperature)
D16-VREF VREF shows BLANK on my diagram
D17-MAP Map Signal Wht/Blu, About 3V KOEO (Varies with Temperature)
D18- Light Green/Blk, Transmission Control Module (A/T Only), N/A
D19 - Red/Wht, Reference Voltage, About 5V KOEO
D20 - Yel/Wht, Reference Voltage, About 5V KOEO
D21 - Blue/Wht, Sensor ground, Less than 1V
D22 - Green/Wht, Sensor ground, Less than 1V

midwesta

up for help

midwesta

okay i got the car running.

it was the o2 sensor, i unplugged it and the car runs fine.

but now my question is:


This:

B14-TDC M TDC -M Wht/Blue, TDC sensor signal, N/A

Was ground to this:

A26-LG1 gound Blk/red, less than 1V

right by the ecu, there was a wire going from A26 to D14. this wasnt actually blowing the ecu cause i had cut that before and it wasnt running. The car runs fine with it cut, but do i need to have a wire going between those two??

theres also 2 wires on plug B going together, but i didnt check which. i cut them when i was trouble shooting and i havent put them back together but the car runs fine and hasnt thrown any codes, but CEL code 41 for oxygen heater sensor (because o2 is unplugged... any ideas???

Ausmith

Double check to make sure that the O2 sensor is not grounding out on a heat shield. That would go for the primary or secondary O2. Sometimes if the metal case makes contact with the body it will ground out and blow the fuse.

Relic1

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by techintegra &raquo;</TD></TR><TR><TD CLASS="quote">B14-TDC M TDC -M Wht/Blue, TDC sensor signal, N/A

Was ground to this:

A26-LG1 gound Blk/red, less than 1V

right by the ecu, there was a wire going from A26 to D14. this wasnt actually blowing the ecu cause i had cut that before and it wasnt running. The car runs fine with it cut, but do i need to have a wire going between those two??

theres also 2 wires on plug B going together, but i didnt check which. i cut them when i was trouble shooting and i havent put them back together but the car runs fine and hasnt thrown any codes, but CEL code 41 for oxygen heater sensor (because o2 is unplugged... any ideas???</TD></TR></TABLE>

D14 - O2 signal
A26 - ground
there's your O2 code problem.

which two wires are connected together on the B connector. that is probibly the reason you popped the emulator. (was it splittime's? I heard his blew up while trying to tune someones car)

midwesta

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Ausmith &raquo;</TD></TR><TR><TD CLASS="quote">Double check to make sure that the O2 sensor is not grounding out on a heat shield. That would go for the primary or secondary O2. Sometimes if the metal case makes contact with the body it will ground out and blow the fuse.</TD></TR></TABLE>

Yeah it was my o2 sensor, thanks Clayton (or whoever is posting on this name).. I am gonna call and schedule for the dyno day at the end of the month and i want to come in for a street tune sometime before.

midwesta

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Relic1 &raquo;</TD></TR><TR><TD CLASS="quote">

D14 - O2 signal
A26 - ground
there's your O2 code problem.

which two wires are connected together on the B connector. that is probibly the reason you popped the emulator. (was it splittime's? I heard his blew up while trying to tune someones car)</TD></TR></TABLE>

Yeah it was my car. but everything that was making my car go wrong was caused by the o2, which was unplugged when dave was tuning, or trying too. So i dont think what happened was my cars fault. but i havent heard from him if his emulator survived or died. If it died i was willing to pay for it.

but i got the car home, just unplugged the o2 and drove it home today. So the only codes i was throwing was 41 for o2 sensor heater and 23 or whatever knock sensor is cause i dont have the knock sensor wired to the ecu (which i will just bypass when its tuned)

thanks for all the help and i will take a pic of my b plug wires in a couple minutes and post them for all to see how hacked up my wiring is (which was not done by me)

midwesta

Okay heres how messed up my wiring is (notice someone used cat5 LAN cable in there)



Heres a close up of plug B (notice the bar wires that are cut (they were always bare i just cut them))


What I can see that is going together:

On the FAR LEFT, the BLUE LAN CABLE goes to:

B15-CKP P CKP -P Blu/Green, CKP Sensor input, N/A
B16-CKP M CKP -M Blu/yel, CKP Sensor signal, N/A

then another wire (the bare one coming towards the ecu parallel with those two in the BLUE LAN cable) goes to:

B2-LG2 ground to shields for CYP & TDC Brown/Blk, Less than 1V


Then on the RIGHT in the ORANGE LAN CABLE goes to:

B11-CYP P CYP -P Orange, CYP sensor input, N/A
B12-CYP M CYP -M White, CYP sensor signal, N/A
B13-TDC P TDC -P Org/Blue, TDC sensor input, N/A
B14-TDC M TDC -M Wht/Blue, TDC sensor signal, N/A

then another wire (the bare one coming towards the ecu parallel with those two in the ORANGE LAN cable) goes to:

B2-LG2 ground to shields for CYP & TDC Brown/Blk, Less than 1V

and on the FAR RIGHT with the BLUE TAPE for the two wires coming from those LAN CABLES is the

B2-LG2 ground to shields for CYP & TDC Brown/Blk, Less than 1V


<u>ANYONE HAVE ANY IDEAS ON WHY THIS GROUNDING WAS DONE?? I CUT THEM AND DROVE HOME 10 MILES JUST FINE</U>

Relic1

holy ****, nice semi cluged wiring job.

the use of LAN cables is actually a good idea, the OEM wiring looks a lot like cat5, since those signals need to be shielded.
the shields should be grounded to B2 just like they did.

I can't really tell what the taped wires are, do you know where they go?

the other end may be messed up. (under the hood)
Do the LAN cables go all the way to the engine or just to the shock towers?

midwesta

okay so i shoud REATATCH everything on the plug B wiring??

the taped wire is a ground and some of the other stuff is shrink wrapped and butt connected (previous VAFC/SAFC install i assume) other than that is good.

but the O2 sensor shouldnt be grounded by the ecu????


so in short put plug B wires back how they were, and leave O2 ungrounded by the ecu or ground it??

midwesta

and im not sure how far the LAN cables go, i DONT think they go all the way into the engine bay, unless the orange and blue covering was taken off...

Relic1

which ECU are you running?

midwesta

p72-a01

i thought i made it abundantly clear in the FIRST [pst. lol jk

Relic1

hay look at that, guess I can't read.


the B plug should be ok the way it was.

A26 should not be jumpered to D14. then try your O2 again. You shouldn't have the CEL anymore after removing that jumper.

If it starts blowing fuses again then there is an issue with the wiring elsewhere.


where are you in chicago?

MugenHonda

look under your dash around the fuse box.
Your grounds should not be grounded, you'll see a batch of wires all black that are grounded, un ground it
That what I did and my vtec ground would stop burning

Relic1

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MugenHonda &raquo;</TD></TR><TR><TD CLASS="quote">That what I did and my vtec ground would stop burning
</TD></TR></TABLE>
VTEC ground?


Modified by Relic1 at 3:54 PM 8/9/2005

midwesta

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Relic1 &raquo;</TD></TR><TR><TD CLASS="quote">hay look at that, guess I can't read.


the B plug should be ok the way it was.

A26 should not be jumpered to D14. then try your O2 again. You shouldn't have the CEL anymore after removing that jumper.

If it starts blowing fuses again then there is an issue with the wiring elsewhere.


where are you in chicago?</TD></TR></TABLE>

I did that but its elsewhere its PAST the plug, its somewhere under the car where the electrical tape and wire loom i used has been cut or melted.

Relic1

under the car? wire tuck?

the OEM wires run out of the firewall (under the battery) to the shock tower, then to the engine.