Wiring for FPDM

[yazuki101]

I am looking for a wiring diagram for the fuel pump driver module circuit on my 2005 Explorer Sport Trac (4.0L). I am getting the error code P1233 and I wanted to test for open circuits, but I am not sure which wires I should be testing on the connector.

Any help would be greatly appreciated, thanks.

 

[2000StreetRod]

P1233 Fuel Pump Driver Module off-line

According to the OBD System Operation Summary for MY 2005:

"Electronic Returnless Fuel Systems (ERFS) utilize a Fuel Pump Driver Module (FPDM) to control fuel pressure.
The PCM uses a Fuel Rail Pressure Sensor (FRP) for feedback. The PCM outputs a duty cycle to the FPDM to maintain the desired fuel rail pressure. During normal operation, the PCM will output a FP duty cycle from 5% to 51%. The FPDM will run the fuel pump at twice this duty cycle, e.g. if the PCM outputs a 42% duty cycle, the FPDM will run the fuel pump at 84%. If the PCM outputs a 75% duty cycle, the FPDM will turn off the fuel pump.
The FPDM returns a duty cycled diagnostic signal back to the PCM on the Fuel Pump Monitor (FPM) circuit to indicate if there are any faults in the FPDM.
If the FPDM does not out any diagnostic signal, (0 or 100% duty cycle), the PCM sets a P1233 DTC. This DTC is set if the FPDM loses power. This can also occur if the Inertia Fuel Switch is tripped.
If the FPDM outputs a 25% duty cycle, it means that the fuel pump control duty cycle is out of range. This may occurs if the FPDM does not receive a valid control duty cycle signal from the PCM. The FPDM will default to 100% duty cycle on the fuel pump control output. The PCM sets a P1235 DTC.
If the FPDM outputs a 75% duty cycle, it means that the FPDM has detected an open or short on the fuel pump control circuit. The PCM sets a P1237 DTC.
If the FPDM outputs a 50% duty cycle, the FPDM is functioning normally."

According to Ford the reason for switching to a returnless fuel system was to eliminate returning hot fuel into the tank thus reducing fuel vapor and consumption.

The fuel pump driver module has a way of reporting its status to the PCM. My cursory review of the source code indicates that when the fuel pressure rail sensor is determined to have failed the FPDM is commanded to a fixed duty cycle and checked to see if it responds correctly to the command. If so, it appears the PCM depends on the intank fuel pressure regulator to control the pressure.

Below is a schematic sent to my by Imp for a 2004. Connections should be similar for your 2005.

I have a larger (more readable) version of the above but can't post it because of size limitation. If you want it, PM me your email address and I'll send it to you.

 

[Markaprice73]

This can also occur if the Inertia Fuel Switch is tripped.

These are known to overheat and/or malfunction. Inspect it for melting at the connector. Also, "smack" it to "trip" it. Then push the red button down to re-set. It's worth a shot. It's located right above where your passenger's right foot would be. (not the best location. My kids used to "trip" it all the time.

 

[yazuki101]

Thanks for the help, I will be sure to check the IFS when I get home from work.

 

[yazuki101]

One last question, if I use an ohmmeter to test the FPDM circuit, do I risk frying my PCM?

 

[2000StreetRod]

disconnect connectors

One last question, if I use an ohmmeter to test the FPDM circuit, do I risk frying my PCM?

Since you will only be testing for continuity between connectors I suggest that you switch the ignition key to Off, disconnect the connectors to the PCM and the FPDM and measure for continuity from PCM connector pin to the associated FPDM connector pin.

 

[yazuki101]

Since you will only be testing for continuity between connectors I suggest that you switch the ignition key to Off, disconnect the connectors to the PCM and the FPDM and measure for continuity from PCM connector pin to the associated FPDM connector pin.

I suppose in order to do that I would something other than a multimeter as well as an assistant. What would be the best method to accomplish this?

 

[2000StreetRod]

monitor duty cycle?

I suppose in order to do that I would something other than a multimeter as well as an assistant. What would be the best method to accomplish this?

If you're asking about monitoring the duty cycle you'd need an oscilloscope, waveform analyzer, or something equivalent to either.

 

[yazuki101]

I meant that if I disconnect the connectors at the pcm and the fpdm, I wouldn't have a complete circuit. So wouldnt I need to have a lead to my ohmeter on each end of the harness?

Thank you for all the help by the way, the electrical is really complex to not have a source for information. I really appreciate it.

 

[2000StreetRod]

correct

I meant that if I disconnect the connectors at the pcm and the fpdm, I wouldn't have a complete circuit. So wouldnt I need to have a lead to my ohmeter on each end of the harness? . . .

That's correct.

 

[gbop]

I am looking for a wiring diagram for the fuel pump driver module circuit on my 2005 Explorer Sport Trac (4.0L). I am getting the error code P1233 and I wanted to test for open circuits, but I am not sure which wires I should be testing on the connector.

Any help would be greatly appreciated, thanks.

On a 2005 Sport Trac with a code p1233, the problem was the fuel cut-off inertia switch. It tripped and would not reset. I held the button down and reached over to start vehicle. Worked fine as long as I held the button.

 

[02lt68]

One last question, if I use an ohmmeter to test the FPDM circuit, do I risk frying my PCM?