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Codes P0708, P0743 and P0755

Tiny
NICKBAR87
  • MEMBER
  • 1999 FORD F-150
  • 5.4L
  • V8
  • 4WD
  • 219,000 MILES
Codes p0708, p0743 and p0755. Truck had trouble taking off as if lack of power and does not shift gears. The original problem I had was that the transmission wiring harness melted to the exhaust. Wiring was repaired and is good again. I have replaced; TPS, transmission internal wire harness, transmission range sensor, torque converter clutch solenoid, and transmission shift solenoid. The only solenoid I have not replaced yet is the transmission pressure control solenoid that attaches to the transmission range sensor. Could that be the issue? Also, when the harness melted I was no longer able to start the truck via the key and had to bypass the key function to start the truck. Could this one solenoid be the cause of my problems?
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Saturday, March 31st, 2018 AT 3:33 PM

14 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,072 POSTS
Hello,

To me it sounds like you have plugged exhaust which would cause all the problems you are describing. Here is a guide to help us confirm the issue:

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Please let us know what happens.

Cheers, Ken
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Monday, April 2nd, 2018 AT 11:13 AM
Tiny
NICKBAR87
  • MEMBER
  • 30 POSTS
No, I know that isn't it. I'm also in the middle of a new exhaust system, so there is nothing after the headers.
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Monday, April 2nd, 2018 AT 12:07 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,072 POSTS
Okay,

With three separate issues I would say the wiring needs to be checked to make sure everything is connecting the way it should.

Here is a wiring diagrams and guide to help you see whats going on:

https://www.2carpros.com/articles/how-to-check-wiring

Let me know what you find, Ken
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Monday, April 2nd, 2018 AT 12:32 PM
Tiny
NICKBAR87
  • MEMBER
  • 30 POSTS
Wiring is sound, no bad wires or terminals anymore. That was already checked and or replaced/repaired.
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Monday, April 2nd, 2018 AT 12:52 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,072 POSTS
With all three codes being different issues and the wiring okay I think we are safe to say the PCM is out and needs to be replaced. Here is the location I would try a used one.

Check out the diagrams (below).

Please let us know what happens.

Cheers, Ken
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Monday, April 2nd, 2018 AT 7:51 PM
Tiny
NICKBAR87
  • MEMBER
  • 30 POSTS
You are mistaken, the website you had attaches is for transmission parts.
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Tuesday, April 3rd, 2018 AT 5:20 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,072 POSTS
I am not sure I follow you, what website?
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Tuesday, April 3rd, 2018 AT 10:55 AM
Tiny
NICKBAR87
  • MEMBER
  • 30 POSTS
Well it may just be a link issue then because every time I try to pull up one of the pictures you sent it directs me to a transmission website.
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Tuesday, April 3rd, 2018 AT 10:58 AM
Tiny
NICKBAR87
  • MEMBER
  • 30 POSTS
But I do know it is not the PCM, I have had it checked out already.
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Tuesday, April 3rd, 2018 AT 10:58 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,072 POSTS
That is strange, when you click on the diagrams I sent you go to a website? The ad is close to the diagrams are you clicking on that? Next lets clear the codes and then just turn the key to the on position without starting the engine and then see what code comes up first.
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Wednesday, April 4th, 2018 AT 10:24 AM
Tiny
NICKBAR87
  • MEMBER
  • 30 POSTS
I have cleared the codes several times, each time I get the same three codes immediately.
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Wednesday, April 4th, 2018 AT 10:26 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,072 POSTS
Have you checked the transmission valve body wiring connector? It sounds like you have a connection problem between the transmission and PCM here are the engine wiring diagrams as well.

https://www.2carpros.com/articles/how-to-check-wiring

Let me know if you need large versions of the engine wiring diagrams.
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Wednesday, April 4th, 2018 AT 10:37 AM
Tiny
NICKBAR87
  • MEMBER
  • 30 POSTS
It seems as if the issue I'm having is that the power source/signal that crosses from the pressure solenoid to the remaining solenoids inside the transmission (4r70w) is not acting correctly, I've replaced the internal wire harness but the pressure solenoid is the only solenoid I have not replaced yet. All if the remaining electrical parts and or wires have been repaired or replaced.
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Wednesday, April 4th, 2018 AT 12:17 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,072 POSTS
Have you checked the transmission range sensor that can cause the problem.
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Wednesday, April 4th, 2018 AT 7:26 PM

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