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Discussion Starter #1 (Edited)
I pulled the DTCs from my EEC (no check engine light was on) and it showed P0232 Fuel Pump Secondary Circuit High. The car runs like sh*t, bucking and uneven, vacuum drifts up and down at steady freeway speeds. The fuel pressure is ok, between 32 and 42 lbs, depending on throttle position. Any ideas? I extended the wiring harness last year, wonder if it's in there???

I was monitoring the car on my way to work this morning. At first it ran well but as it warmed up it started to run rough. I noticed that the short term fuel trim % on bank 1 would go to as high as 42 while bank 2 would be at -0.8 or so. The long term trim on bank 1 would show 24 while bank 2 was at 1 or 2. Anyone have a clue as to what may be going on?
:leftright
 

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Discussion Starter #3 (Edited)
Another clue is that when the car runs rough it is in closed loop mode. That's when the trim values on bank 1 go high. It alternates between closed and open loop. When in open loop the trim values are low and approximately the same on both banks. Today I got "Closed loop, but fault." on the readout.

I'm going to check the wiring harness that I extended, maybe it's got a bad solder joint or a short.
 

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Continuous Memory Diagnostic Trouble Code P0232 indicates that one of the following possible conditions has occurred:
<UL>
<LI>Fuel pump circuit activated when PCM expected circuit to be off 9IE fuel system test or prime procedure).</LI>
<LI>Inertia Fuel Shutoff switch was tripped, then reset.</LI>
<LI>Open circuit in or between the fuel pump and Fuel Pump Monitor (FPM) circuit at the PCM.</LI>
<LI>Poor fuel pump ground.</LI>
<LI>FPM or power-to-pump circuit short to power.</LI>
<LI>Fuel pump relay contacts stuck closed (IE CCRM).</LI>
<LI>Engine stall due to excessive load (IE TCC solenoid).</LI></UL>
To test for a open or short condition:
Get a scan tool with the Key on, engine off. Access FPM PID. Observe the FPM PID for an indication of a fault while performing the following (the FPM PID will turn ON when an open or short to power is detected):
<UL>
<LI>Shake, wiggle, bend the Power-to-Pump circuit between the CCRM Pin 5 and the fuel pump.</LI>
<LI>Shake, wiggle, bend the fuel pump ground circuit from the fuel pump to ground.</LI>
<LI>Lightly tap the fuel pump to simulate road shock.</LI>
<LI>Lightly tap Inertia Fuel Shutoff switch to simulate road shock.</LI>
<LI>Lightly tap the Low Speed Fuel Pump Relay (4.6L 4V Mustang).</LI>
<LI>Lightly tap the CCRM to simulate road shock.</LI>
<LI>Shake, wiggle, bend the FPM circuit between the PCM and the splice to the Power-to-Pump circuit.</LI></UL>
Next turn the Key off and inspect the fuel pump vehicle harness connector and the fuel pump ground for corrosion, damaged pins.

If a fault is indicated service as required.


I for one would lean to the SCT tune if you did it yourself. You may have made a typo.
 

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Discussion Starter #5
Looks like that p0232 was a one time thing. It never did that again. But the rough running when it gets hot, flipping back and forth between open and closed loop with the message "Closed loop (but fault)" showing often. I programmed the EEC with the stock program and had the same problem as soon as it reach operating temps just sitting in my driveway. I burned the custom tune from Rienhart and it is still doing the open/closed loop dance .

I've replaced the coolent temp sensor, the upstream O2 sensor on the passenger side, replaced the EGR solenoid and the EGR valve. A stethesope indicates that all the injectors are opening and closing. Seems like it might be the EEC.
 

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i can just about tell yea that it is the computer one way of testing ive heard is to check the #2 injector with a teslight while the car is running the test light should blink being that the injector is opening and closing. Ive heard alot of times that are cars are prone to pcm malfunction
 

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bigbird said:
I programmed the EEC with the stock program and had the same problem as soon as it reach operating temps just sitting in my driveway.
Just for kicks see if both your low and high-speed fan is working. I have found that stalling will occur at higher temperatures if the high-speed fan does not kick in. After I fixed the fan I took a closer look at the temperature set points in my EEC and decreased the high-speed fan start time. I believe my higher compression was at fault for the temperature requirement.

If you do not have a scanner you can check the resistance (ie for shorts). To do this turn off the car and disconnect the fan motor. Be careful not to break the connector like I did. You can check the resistance between the motor connectors. Resistance should peg the scale between two the ends and the center wires. If not you have a suspected bad fan motor.

If not I will look for shorts in the fuel system anyway. Shorts come and go...
 

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Discussion Starter #8
I installed a new Ford O2 sensor even though I didn't really think that was the problem, but it was! It's running great again. The sensor I replaced was not Ford/Bosch and had only about 20,000 miles on it. Last time I cheap out on sensors.

I wonder why I had no check engine light and no codes?
 
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