hardstart with codes P0191 & P1233

[mrlucas]

Hello All. I am a new member and have a problem 2004 Explorer giving codes P0191 & P1233. I have identifed what the codes mean, but not how to fix. I took it to a mechanic last week with no check engine light or known code, it has been "hard starting" and gradually getting worse. It was intermittent and when it occurred it would generally start on the 3rd try (have not touched the gas pedal). The mechanic charged me $100 for diagnostic, said he found 3 codes though I don't know what they were, and cleaned a few things. He said he could not replicate the problem. He said he cleaned a few things and and through all the TSBs and the only thing he might reccomend would be to change the fuel filter.

Well, it has gotten much worse since then. It in fact had an issue with the starting when I went to dpart the mechanic's, nothing was fixed or diagnosed. Now difficult to start every time and sometimes lugs when it does and the check engine light came on. i have my own code reader and got P0191 "fuel rail pressure sensor circuit range/performance" & P1233 "fuel pump driver module off line". Is there a sensor that needs replacement or the fuel pump? Would a fuel filter make a difference. Please help.

Thanks, Shane

 

[2000StreetRod]

Change fuel filter

I'm not familiar with the newer Explorers but if you haven't changed the fuel filter in the last 30,000 miles I would do that and follow it with adding fuel injector cleaner to the fuel tank.

If there is a fuel pressure test port then I would check the pressures.

If the fuel pressure is low then check the fuel pressure regulator.

That's off the top of my head. I'll try to find out what conditions sets the two DTCs you've read. What engine do you have?

 

[2000StreetRod]

DTC criteria

According to the Ford 2004 OBD System Operation Summary:

There is a fuel rail pressure sensor that is tested by the PCM. P0191 is set when demand minus actual is greater than 40 psi.

"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."

Its not the inertia fuel switch or you wouldn't ever get fuel pressure to start. I suspect either the fuel rail pressure sensor or the Fuel Pump Driver Module. I still suggest testing the fuel pressure if there is a test port.

 

[mrlucas]

Thanks

Thanks for the replies. It appears to be the fuel rail sensor. I am changing the fuel filter as well.