This 2004 4.6 X engine just started surfacing a P1237 error (fuel pump secondary circuit fault). This car has been mostly sitting, it has 9200 miles on it.
I took it out of storage it had a bad hesitation problem during acceleration, any load above 2k rpm, (it did have some drivability issues prior to storage but never threw an error). After I replaced the fuel filter it ran great for about 10 miles. I opened the filter and it looked clean, the pores my have been plugged but it looked clean. I just surfaced the p1237 this am but can't find any troubleshooting information. Does anybody have shop manual detail or personal experience on a P1237.

 

Just joined and love this forum already. After my initial post I started searching and found some great info from ckiffyk (Great tech info) and koolersl2. I have a lot to check out, thanks guys.

 

Where is the FPDM, fuel pump driver module located?

 

Followed the wires back to the trunk side of the left rear fender. Partially dropped the tank found nothing wrong, ordered the FPDM.

 

The fuel pump driver module fixed my hesitation problem. Prior to replacing the module , with a scanner I could see the fuel rail pressure dropped from 40 lbs to 5, the pump voltage dropped instead of increesing.