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Pcm fuse blowing

Tiny
RICKROHIO
  • MEMBER
  • 2001 FORD TAURUS
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 100,000 MILES
Hello. The 30 amp pcm relay fuse under the hood blew the other day leaving my wife stranded. I tried replacing it back it pops immediately after you turn the key to run. I am trying to figure out where to start tracking a short. There was a remote starter installed on this car a few years ago, but my understanding is the pcm circuit is not affected by this wiring. We also had the heater core replaced this past summer. Is it possible a wire could have gotten pinched and has now rubbed through. I thought about unplugging the pcm module and testing. If it still shorts then I know it's something else. What else is on this circuit.

Thanks
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Sunday, December 27th, 2009 AT 9:06 AM

15 Replies

Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Nothing else is on that fuse..change the relay in spot 31, that's the PCM power relay.


https://www.2carpros.com/forum/automotive_pictures/62217_relays_2.jpg



https://www.2carpros.com/forum/automotive_pictures/62217_PCM_Relay_1.jpg

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Sunday, December 27th, 2009 AT 10:23 AM
Tiny
RICKROHIO
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  • 7 POSTS
Ok. Replaced the relay and nothing different. Fuse blows instantly. It doesn't if the relay is out. Any other ideas?
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Monday, December 28th, 2009 AT 9:31 AM
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Pull that power distribution box and check for any sign of burnt or melted wires, if non found, remove negative battery cable, unplug the PCM, re attach battery cable and see if it blows with PCM out of the circuit, it may actually need a new one! Check wire colors at PDC and trace for shot at PCM connector.
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Monday, December 28th, 2009 AT 1:42 PM
Tiny
RICKROHIO
  • MEMBER
  • 7 POSTS
The problem is I can't find the pcm module. Can you give me some guidance as to where it's located?
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Monday, December 28th, 2009 AT 2:16 PM
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Right side on the firewall.
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Monday, December 28th, 2009 AT 3:06 PM
Tiny
RICKROHIO
  • MEMBER
  • 7 POSTS
Ok. Found the pcm. I unhooked it and now the fuse doesn't blow. Does that indicate the pcm itself, or?
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Monday, December 28th, 2009 AT 6:36 PM
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Probably. If it was a pinched power wire it would still blow. Your problem now is with Ford the new PCM needs to be programed to your cars hybrid electronic cluster, and pats module, or it wont start. This require a Ford tool to do it, probably a trip to the dealer.
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Tuesday, December 29th, 2009 AT 1:38 PM
Tiny
RICKROHIO
  • MEMBER
  • 7 POSTS
Ok. Removed all of the remote starter, wires, etc. Didn't see anything that would be shorting. Reconnected the pcm module and the battery, and installed a new fuse. Car started fine. I shut it off and start again. Good to go. Shut it off and button up the dash and glove box. Start it again, open garage doors and put it in gear it dies. I restart it and let it warm up. When I put it in reverse no problem, but in drive it sputters and dies. I restart and let it warm up. Put it in drivr and pull out of the garage. I don't give it any gas at this point. I stop outside the garage and close the doors. When I get back in, I put it in drive and start to drive it up to the house. It is downhill slightly outside the garage so I don't have to give it gas. I get in the main driveway and give it gas. As soon as I do it dies and the fuse is blown. I tried putting another one in but it blows immediately. Totally lost now.

When we had the heater core replaced this summer the indicator light on the gear selector didn't work when we got it back. Could this have anything to do with it?

It seems like we reset a sensor when we disconnected the battery and the car had to run for a little bit before it resent the shorted signal to the pcm.
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Tuesday, December 29th, 2009 AT 2:53 PM
Tiny
MERLIN2021
  • MECHANIC
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Is the check engine light on? does it come on when you turn the key to the on position, then go out after the car starts? Can you try scanning for codes? If any codes in the P0600 range come up, these are PCM codes. It would need to be a power wire if it blows the fuse, but the fuse only blows with the PCM attached...I cant promise anything, but a faulty sensor input may cause the problem, try unplugging 02 sensors one at a time and see what happens.


https://www.2carpros.com/forum/automotive_pictures/62217_PCM_Connector_4.jpg


Check pin 71, should be a red wire it's power from ignition. If as you say it doesnt blow until it warms a bit, I still say disconnect the 02 sensors, they are out of the loop during warm up then come online...another quetion, do you have the 24 valve engine or not? Will fuse blow with engine off and shifting into drive with key in "ON" position?
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Tuesday, December 29th, 2009 AT 3:38 PM
Tiny
RICKROHIO
  • MEMBER
  • 7 POSTS
The check engine light was not on when the car started and ran. Of course now it's on when you turn on the ignition, but it would be without the car running. I am getting more fuses in the morning and I'll try disconnecting the o2 sensors. I tried disconnecting the battery and letting it sit for 10 minutes or so but the fuse still blew. I would think whatever let me start the car would reset again. I will try disconnecting the pcm again to see it I can get it to reset.

Before this started the check engine light was on because of an o2 sensor that I hadn't replaced. So I will try it when I get new fuses and see.
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Tuesday, December 29th, 2009 AT 4:04 PM
Tiny
MERLIN2021
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When you pull the PCM connector off again, inspect the both sides of the plug for bent or pushed out pins, or green corrosion goo.
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Tuesday, December 29th, 2009 AT 4:18 PM
Tiny
RICKROHIO
  • MEMBER
  • 7 POSTS
Ok. More clues. I reconnected everything and put in new fuse this morning. Started fine. Backed it back into garage. Ran it through the gears. No problem. This is with the two o2 sensors that I could reach from the front disconnected. I let the car warm. Not to operating temp but until the gauge moved. Went through the gears again and as soon as I put it in drive the fuse blows and the car dies.

My wife has been complaining since we got the heater core replaced that the light on the gear selector didn't work, but I just noticed that the indicator on the dash doesn't work either.
It seems like if it was a pinched wire it wouldn't wait till it warmed up, but who knows. Maybe transmission temp sensor?
But why drive?
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Wednesday, December 30th, 2009 AT 9:58 AM
Tiny
MERLIN2021
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Might be the WAY the engine is tilting when in drive, in reverse the motor tilts forward in drive it leans towards the firewall, check the ground wires that attach to the motor, and connectors at all points that contact the engine. Tranny too! Check wiring harnesses for chffing marks, then open the conduit up and look fo any sign of rubbed thru wire insulation.
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Wednesday, December 30th, 2009 AT 1:06 PM
Tiny
JARED LAYMAN
  • MEMBER
  • 1 POST
Wondering if you ever found the solution for your problem? I am having the exact same symptoms. Thanks
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Sunday, April 21st, 2019 AT 8:34 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,643 POSTS
Hello,

PCM fuses blow when a fuel injector shorts out. Please disconnect all injectors and replace the fuse to see what happens. This guide will help you test the injectors:

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

Please run down this guide and report back.
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Wednesday, April 24th, 2019 AT 3:51 PM

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