code 59 low fuel pump voltage


New Member
Oct 24, 2020
Riverside, california
I'm haveing this issue with my buddys 95 mustang gt with the 302 . Its throwing code 59 which I believe is for low voltage to the fuel pump . It started throwing this code after I replaced the motor (old one was knocking ).

It has a driveablity issue where it idles rough and lacks power under load

From the get go the fuel pump was bad , it was louder than the exhaust ( no cats ) and it took 5 or 6 tries o start the car
I replaced the following
Fuel filter
Fuel pump
Fuel pressure reguator + vacuum hose for it
The car starts on its first try now . It keeps 35 psi while idleing and goes up to 40 psi when you accelerate
But still gives the driveablity issue where it'll want to die out under load , runns rough and throws code 59 .

I read some really good diagnosis about testing the voltage to and from the fuel pump and to and from the ccrm and diagnosing bad fuel pressure.

So I started from the 4 pin connection to the fuel pump had 14 volts from the brown and pink wire going to the pump .
I had 14 volts coming from the inertia switch to the fuel pump
- i had and extra one laying around so I replaced the computer and the ccrm and still having the same issues ,I'm thinking its the wireing somewhere

My question is how does the computer know what voltage the fuel pump is getting? Because thats most likely where my problem is ?
Any information or wire diagrams would be much appreciated
(Will keep the post updated TY)
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