Author Topic: 1997 Ford Expedition PCM fuse blows  (Read 11552 times)

  • Guest
1997 Ford Expedition PCM fuse blows
« on: August 09, 2005, 11:11:55 AM »
  I have a 97 Expedition (Eddie Bauer), 4WD, 4.6L that cranks, but will not start.  I had replaced the battery just a couple days before and the theft light was flashing so we assumed it had something to do with the anti-theft system.  We towed it to Ford and they  reprogrammed our keys, but it still didn't start.  They did a diagnostic and told us that there is a "short" somewhere among the 200+ feet of wiring in the engine that is causing a fuse to blow.  (Ford wanted $99 per hour to find the short.  I said NO WAY!)
Fuse #24, a 30 amp fuse, that goes to the PCM power is blowing each time I try to start the vehicle.  

Do I just replace the PCM or is there some wiring I can check first?  Could this short be related to another part of the engine or is it most definitely the PCM?   Confused  Confused

Share via delicious Share via digg Share via facebook Share via linkedin Share via reddit Share via stumble Share via twitter

Advertisement

  • Guest
(No subject)
« Reply #1 on: August 09, 2005, 01:43:20 PM »
7csranch,
That fuse supplies power to a lot more than just the PCM. The fuel pump relay, MAF sensor, canister vent solenoid, all fuel injectors and the heated O2 sensors are just some of the items on that circuit. So replacing the PCM at this point would be taking an expensive stab in the dark.

You would first need an accurate wiring diagram to determine everything fed by that fuse and then you would have to check each circuit individually for a short. You would also need to know the specific resistance or current draw limits for each of the components such as relays or solenoid windings which are supplied power by that circuit. There?s a good chance that one of the many wires which distributes the power in this circuit has shorted to ground so it might be worth your time to do a close inspection of all visible wiring in the engine compartment?..you might get lucky and find it.

Usually finding the cause of problem like this is very tedious and time consuming work which requires the proper equipment, knowledge of automotive electronics and access to specific information which is why this type of work is so expensive.

Share via delicious Share via digg Share via facebook Share via linkedin Share via reddit Share via stumble Share via twitter

Advertisement

  • Guest
great!
« Reply #2 on: August 09, 2005, 02:48:49 PM »
Confused Well that sounds easy enough!  J/K!!!  The owner's manual only lists the PCM as being protected from that circuit.  Apparently we have to spend a lot of time checking wires!  I don't live anywhere close to a repair shop so unfortunately this is a DIY project.

I do have the Chilton's book, but their wiring schematics are a little difficult to read.

Thanks a lot for the reply.  I appreciate it!

Share via delicious Share via digg Share via facebook Share via linkedin Share via reddit Share via stumble Share via twitter

Advertisement

way2old

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 2187
  • Karma: +3/-0
    • View Profile
(No subject)
« Reply #3 on: August 09, 2005, 05:54:16 PM »
Can you hear the fuel pump run for about 2 seconds when the key is first turned on??  If not, unplug fuel pump and see if fuse still blows.  If you have the owners manual, it will show all the circuits that are protected by that fuse.  Then you can disconnect each component one at a time till you find the bad circuit.  Let me look and see if Ican find diagram of fuse.  Will get back to you.
« Last Edit: December 31, 1969, 06:00:00 PM by way2old »

Share via delicious Share via digg Share via facebook Share via linkedin Share via reddit Share via stumble Share via twitter

  • Guest
(No subject)
« Reply #4 on: August 09, 2005, 06:08:16 PM »
I have one fuse left.  I'll try your suggestion with the fuel pump, but if that doesn't work I'll have to wait til I can get more fuses (I'm 45 miles from the nearest parts store...or any store for that matter).  Those fuses are expensive when you keep blowing one after the other!

The only circuit that the manual lists as being protected is the "powertrain control module power".  There is one yellow & black wire coming out of the fuse slot.  Chilton's shows that wire going to the pcm power box.

Thanks for the help!

Share via delicious Share via digg Share via facebook Share via linkedin Share via reddit Share via stumble Share via twitter

way2old

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 2187
  • Karma: +3/-0
    • View Profile
(No subject)
« Reply #5 on: August 09, 2005, 06:47:01 PM »
If it is the 30 amp maxi fuse under the hood, it also powers up fuse 1 mini 5 amp fuse for the PCM.(this one is in a small fuse holder on the fender behind the underhood fuse panel)  So if the PCM was faulty, I think the 5 amp would also blow.  The fuse under the hood powers up the PCM relay which feeds a lot of other sensors and components.  Does the fuse blow as soon as the key is turned on or as the starter is engaged?  Soooooo, about all I can say is "Have Fun!!!"  If we can be of any more help, just holler. I have the diagrams, but if you are not used to Ford manuals, they are very hard to read.  It may take 15 pages to get all the wiring on just that one circuit.
« Last Edit: December 31, 1969, 06:00:00 PM by way2old »

Share via delicious Share via digg Share via facebook Share via linkedin Share via reddit Share via stumble Share via twitter

rtedd

  • Newbie
  • *
  • Posts: 1
  • Karma: +0/-0
    • View Profile
Re: 1997 Ford Expedition PCM fuse blows
« Reply #6 on: January 23, 2011, 11:56:17 AM »
There is also another PCM fuse other than the # 24 30 AMP.  It is in the smaller fuse box right next to the under hood fuse panel where you were looking at the #24. It is the #1 fuse in the smaller panel. It is a 5 AMP black Ford fuse.

Share via delicious Share via digg Share via facebook Share via linkedin Share via reddit Share via stumble Share via twitter

diyer87

  • Newbie
  • *
  • Posts: 1
  • Karma: +0/-0
    • View Profile
Re: 1997 Ford Expedition PCM fuse blows
« Reply #7 on: March 21, 2011, 08:47:17 PM »
I have a similer prolem on a 2005 sunfire.  The PCM 10 amp fuse blows instantly when pluged in... I took the battery out and tested it and it is shorted to ground...I bought the chilton for the car and following the wiring diagram I made it back to the PCM and when I unplug the harness that the line coming from the fuse is in the line is no longer shorted...I pluged that harness back in and unpluged the harness on the other side of the PCM, once again the short is not there.  Going from there I am assuming all I need to do is follow which wires coming out of the PCM in that harness are supposed to be hot and test the ohm's to the engine block...when I find one with low resistance I have found my short.  Does this all sound correct?

Share via delicious Share via digg Share via facebook Share via linkedin Share via reddit Share via stumble Share via twitter

Digitale

  • Newbie
  • *
  • Posts: 1
  • Karma: +0/-0
    • View Profile
Re: 1997 Ford Expedition PCM fuse blows
« Reply #8 on: June 13, 2012, 10:43:10 AM »
I know this was a older thread, however I am haveing this same issue, with the exact same type of vehicle.... I am just looking for a little direction.....I have replaced the PCM and still blows the 30 amp fuse when key is turned on... Thanks in advance...

Share via delicious Share via digg Share via facebook Share via linkedin Share via reddit Share via stumble Share via twitter


Share Topic

Share via delicious Share via digg Share via facebook Share via linkedin Share via reddit Share via stumble Share via technorati Share via twitter

Similar Topics

  Subject / Started by Replies / Views Last post
xx
1997 Ford Expedition, 8 cyl, headlight switch

Started by

2 Replies
2779 Views
Last post April 14, 2008, 08:13:11 PM
by discretesignals
xx
1997 Ford Expedition: Hard to Shift/Repair

Started by

1 Replies
3079 Views
Last post March 27, 2010, 04:42:35 PM
by discretesignals
xx
1997 FORD EXPEDITION EDDIE BAUER MODEL NOT 4X4

Started by

1 Replies
1361 Views
Last post November 12, 2004, 09:14:07 AM
by way2old
xx
Warped front brake rotors 1997 Ford Expedition

Started by

1 Replies
1937 Views
Last post September 08, 2003, 01:59:35 PM
by trust
xx
1997 Ford F150 Trailer Light Fuse

Started by

2 Replies
9733 Views
Last post July 09, 2008, 11:53:06 AM
by