95 Bronco XLT 5.0L - Fuse #18 blows

Hello all,

I know this has been discussed maybe 100 times, and I have read about 50 pages, but I have not found the cause yet so I asking for patience and assistance. Fuse 18 is shorted to ground. Speedometer and odometer do not work. Transmission shifts hard because the PCM cannot sense the speed to tell the tranny when to shift. No accidents or repairs prior to the problem. It worked one day and stopped the next. No other fuses are blown.

Wiring diagrams in my Haynes manual show fuse 18 goes only to PSOM and ESCM (Electronic Shift Control Module) so I guess I need an updated manual. I have found other diagrams showing fuse 18 is for PSOM, ESCM, air bag module, brake interlock solenoid, and overhead console. Note, my bronco does not have an overhead console. Maybe there are wires are under the head liner or trim, I don't know.

The problem is NOT the ESCM, PSOM, brake interlock solenoid, nor air bag module. The ESCM was disconnected and removed. Still shorted to ground. The instrument cluster was removed. Still shorted to ground. The brake interlock solenoid was disconnected. Still shorted to ground. The air bag module under the coolant reservoir was disconnected. Still shorted to ground. I can see the back side of the fuse block. The white-ppl wire comes straight out the back so the problem looks to be inside the wiring harness unless I am missing another device.

A family member needed the vehicle so I ran a wire with an add-on fuse from the ignition side of fuse 18 to the PSOM. The speedo, odometer, and tranny are working fine. We don't need 4x4 so I am not concerned with the ESCM at this time. Also, we normally press the brake before shifting out of park so no issues here. However, I would still like to find the problem.

Thank you,
Tom

Yo Tom,

If you have the Electronic Day/Night Mirror, look at the BLACK/PINK (BK/PK) stripe wire to the Electronic Day/Night Mirror, it's wired into the backup lights and is on the fuse #18 circuit. 



pic by twirlyboggs

Free registration for some wiring diagrams (partial, 86 through 96) and Technical Service Bulletins, (80 through 96) same as by Ford;

 http://www.revbase.com/BBBMotor/Wd

from 96 Bronco Workshop Manual

Yo,

Also from 96 Bronco Workshop Manual;




Item


Part Number


Description


1


14A509


Wiring Assembly


2


14401


Wiring Assembly


3


381801-S55X


*****


4


—


Install Locator in Hole Provided (Part of 14A509)


5


N805375-S36MG


***** to Weld Nut


6


14A504


Wiring Assembly


7


—


To Ground (Part of 14301)


8


14A504


Wiring Assembly


9


19A123


Wiring Assembly


10


14A509


Wiring Assembly


11


14A163


Clip


12


14A265


Wiring Assembly


13


—


To Radio Speaker


14


—


To Power Window Lock Switch


15


—


To Power Mirror Switch


16


—


Install Locator in Hole Provided (Part of 14632)


17


—


To Door Disarm Switch Pigtail (Part of 14A509)


18


—


Door Lock Actuator


19


—


To Courtesy Lamp


20


—


Locator, Install in Hole Provided After Water Shield Is Installed


21


—


Power Window Motor (Part of 1023200)


22


—


To Power Mirror Pigtail


23


14632


Wiring Assembly, Rear Door


24


—


To Vanity Visor Pigtail


25


—


To Overhead Console (Bronco Only)


26


98519A58


Overhead Console (Bronco Only)


27


—


Used with Remote Keyless Entry Only


28


17K745


Illuminated Vanity Visor/E.C. Mirror/Overhead Console


29


—


Install Shield into Mirror Base (with E.C. Mirror)

Many thanks for the help. No, I do not have electronic day/night mirror but the wires could still be there. It will take some time to check the harness at various places. I will keep you posted. Thanks again.

Yo G,

Yw! Appears the harness runs up driver side A pillar under trim.

Our 96 has connectors for many items that weren't included such as daytime running lights, etc. 

If I remember a conversation I had with the guys down at my Dealership. DTRLs would/could of been a required feature for a Canadian Vehicle. Ford probably saved money by using the same wiring harness for everything and plugged in what the build sheet called for.

Hello,

I have a 1996 Bronco that the wife and kids wont let me sell.  Now I've run into this #18 fuse problem.  I've checked the day/night mirror, but had zero luck finding anything.  I went further to change out my speed sensor in the rear diff, and Engine ECM(ECU), but no luck.  The fuse blows in about 2 seconds every time I replace it.  The only thing I've don't prior to this issue was change out the battery.  I've checked around the battery too, but nothing looks broken.  Help!

Yo Robert,

Welcome!

Same here, everyone want to keep our 96 too, including me. 

MAJOR EDITS!!

Have you pulled the plastic trim panels? From mirror to driver side HORIZONTAL & VERTICAL PANELS?

EDITS BELOW:

The overhead console has been a known trouble spot, sheet metal ***** piercing the wiring.

The PSOM is the module that converts the VSS signal from analog to digital and sends it to the PCM - is your speedometer working?

Is E4OD shifting OK?


Air Bag module is under the dash - IIRC, it says "Air Bag" on it.

UNDER THE DRIVERS SIDE OF THE DASH YOU NEED TO UNPLUG THE AIRBAG MONITOR. IT IS A BLUE BOX WITH A COUPLE CONNECTORS IN IT.  IT IS LOCATED UP AND TOWARDS THE CENTER OF THE DASH. UNPLUG IT AND REDO THE FUSE. DOES IT BLOW?

Air Bag Diagnostic Monitor Location pic in 94-96; as Steve83 pointed-out, "...The module I MIS-labelled as "Airbag" is actually the Wiper Control Module (WCM). The Airbag Diagnostic Module (ADM) is light blue, wrapped in black foam, above the gas pedal..." 
Source: by Ryan  see ATTACHED pic

"...If the Air Bag indicator is flashing code 51 and a short to ground has not been serviced, this means that an intermittent short to ground exists in the air bag system. The diagnostic monitor should be replaced only after service of the intermittent short has been completed; The Airbag Diagnostic Module (ADM) is light blue, wrapped in black foam, above the gas pedal; Check Front Sensor/ wiring First..." READ MORE
Source: by miesk5 at Ford Bronco Zone Forums


Borg Warner 1356 Electric Shift on the Fly Transfer case Shift control module is behind the right side (passenger side) kick panel.


Brake Shift lock actuator keeps you from shifting out of PARK unless the brake pedal is pressed, it's next to the steering column (under the dash).

Brake Shift Interlock; "These (and many other) vehicles are equipped with a Brake/Shifter interlock for safety. This system requires the driver to hold the brake depressed before the shift lever can be moved from the Park position. There is an actuator (solenoid) on the left side of the steering column under the dash that disengages the shifter lock when the brake is depressed. In the event this system malfunctions, the shift lever may be stuck in the Park position. One cause of this complaint may be due to a faulty brake switch circuit. If you experience this complaint always check for blown fuses and brake light switch operation before proceeding with other work."

Brake Shift Interlock Wiring Diagram is attached


The day/night mirror and the overhead console locations are self explanatory.

Yo Robert,

Overhead Console Wiring Diagram & better quality Air Bag Wiring Diagram attached. 




NOTE: Whenever a wire is labeled with two colors, the first color listed is the basic color of the wire, and the second color listed is the stripe marking of the wire.




WIRE COLOR CODES




Code


Color


Code


Color




BL


Blue


N


Natural




BK


Black


O


Orange




BR


Brown


PK


Pink




DB


Dark Blue


P


Purple




DG


Dark Green


R


Red




GN


Green


T


Tan




GY


Gray


W


White




LB


Light Blue


Y


Yellow




LG


Light Green


—


—





Check W/P wires for the short in all listed components.

It's mostly white with a purple stripe



1356 Electric Shift Control Module Wiring Diagram is attached
Source: by Troll Banned (Bronco Rob, BroncoRob)

Module is  behind the passenger kick panel

Inspect W/P wire in harness that TRAVELS from the module plug to the back of the transfer case, especially at transfer case.

Brake shift lock actuator near the ignition switch , you may have to pull the covers off just UNDER & behind the steering wheel.

Yo Robert,

I keep being logged off!

See attached Air Bag Diagnostic Monitor Location pic in 94-96; as Steve83 pointed-out, "...The module I MIS-labelled as "Airbag" is actually the Wiper Control Module (WCM). The Airbag Diagnostic Module (ADM) is light blue, wrapped in black foam, above the gas pedal..." 
Source: by Ryan  

Wow, you are my new best friend.  I took the trim around the windshield off completely. All the way around the window and up through the overhead console and it all checked out ok.   I've also replaced the ECU, and the rear speed sensor in the rear axle (I saw another post somewhere saying that could be the problem).  I've been at work for a while, but I'm home now and planning on getting right on your other ideas this morning.  I'll get back with you to let you know how I made out.  Thank you for the direction.  

Robert

Yo Robert,

Good that you're hanging in there!

I knew many automotive electrical repair shop close since the advent of OBD 2 and accessories that repairs cost so much that they lost custoners and eventually closed.

That was the culprit!

I unplugged the Airbag Control Module and now the fuse does not blow.  So, now to find a decent place to find a new or rebuilt one.  I hate the rebuilt stuff.  They usually go bad soon after they're installed.  Do you recommend any good retailers who sell them?

Robert

Well, it looks like its going to be a challenge finding a new module.

Yo Robert!

You are the  HANDS-ON-GOT 'ER DONE MAN

Google, 1995 bronco air bag module

Most if not all are used, so for example;

https://www.ebay.com/itm/1995-Ford-F250-Airbag-Air-Bag-Control-Module-Unit-OEM-LKQ/312741891070?fits=Year:1995|Model:Bronco&hash=item48d0de8bfe:g:qbIAAOSwMT5dYIZn&redirect=mobile

Are you a -DIYer too?

Diagnostic Monitor Thermal Fuse Replacement Video in a 94; "...WARNING: working on airbag systems is inherently dangerous. should you choose to do anything depicted in the video i cannot be held responsible for anything that may happen. My bronco was flashing a code 51. this stands for "internal adm fuse blown due to intermittant short to ground". the general repair for this is to fix the short and replace the aibag diagnostic monitor. i called the junkyard and they wanted $55! so i decided that instead of replacing the whole thing i would only replace the component that was broken. the thermal fuse in the ADM is 168 deg C, this is a hard to find temp rating so i bought some rated 1 degree lower at 167 deg C. i bought mine from newark.com. the ones i bought ended up being slightly larger that the original so i had to modify the fuse's casing to fit it. in retrospect if you were to do something like this it would be easier to remove the fuse assemby from a ADM in a vehicle with a deployed airbag, just make shure the fuse itself has continuity. if you show the fuse to the people at the junkyard the fuse and they ask what its from make something up or tell them its from a blown airbag module. this method would require less modifying and would look much more professional. applies to 1994-1996 broncos and f150s..."
Source: by pfun41

Direct to video @ 

Well, by nature I'm a DIY'er, but I work full-time, I'm the father of three young kids, and my wife travels for a living. So my tinker time is very limited. So I'd rather find a new one on this issue.  I watched that video earlier today, lol.  Anyway, I'm looking for a local circuit board service to take it for repair.  We'll see!  Thanks for your help.  I'll keep you updated on my success.

Thanks for this thread. It helped me find the culprit (Air Bag Control Module) responsible for a constantly blowing #18 fuse. Now, to try and locate a replacement module.

HUGE thanks from me too on this thread. My issue was the black/pink wire in the rear view mirror, fixed that and all the issues went away!