Help Please....miffed About 99 Gt Not Starting.....


Nov 14, 2013
i replaced that inertial switch in the trunk and the car sometimes still wont battery,etc.....i dont know if its me...but the car does it mostly when its cold outside......sometimes i turn the key to on and dont hear the whirring of the fuel pump....sometimes i do....the fuel rail valve wont expel any gas when this happens....bad fuel pump? or?...oh btw the computer pulled a p1233 code...also a c1145....
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It would be helpful to know:
  • the Model year of your Mustang.
  • When this problem occurs is there +12 volts confirmed at the IFS switch?
  • What is the condition of the ignition switch? Is it loose and sloppy?
99 gt.......12 volts at the ifs switch which i just replaced......ignition switch is play at all....and....i have noticed this has happened dont know if its by coincidence or if its has been very cold the last 3 times when this has happened....
Double check the ground located in the trunk. This is one of the possible causes listed for the P1233 DTC code. However, the P1233 code tends to rule out a bad fuel pump as the primary cause.

If the ground is good and there is +12 volts at the IFS switch (confirmed), then the problem is in the FPDM, fuel pump, or PCM.

Note, it's important that the voltage at the IFS switch be confirmed while the problem is occurring.

P1233 - Fuel System Disabled or Offline

  • Inertia fuel shutoff (IFS) switch needs to be reset
  • Open FPDM ground circuit
  • Open or shorted FPM circuit
  • Damaged IFS switch
  • Damaged FPDM
  • Damaged PCM
  • Also for Escort/Tracer and Mustang:
    • Open FPDM PWR circuit
    • Open B+ circuit to constant control relay module (CCRM) pin 11
    • Open ground to CCRM pin 18 (Mustang)
    • Damaged CCRM