P1234 - FAULT CODE - OBD2

POST UPDATED IN January, 2023

P1234 Code failures by brands

P1234 FORD, LINCOLN, MAZDA, MERCURY: FUEL PUMP DRIVER MODULE DISABLED OR OFFLINE

Description of DTC code P1234

The fuel pump is used in the combustion system of vehicles and its purpose is to transport fluid from the fuel tank to the engine. Fuel injection engines typically use electric pumps located inside the fuel tank. The fuel pressure must meet certain specifications in order to achieve optimum engine performance.

The fuel pump control module checks the voltage supply to a vehicle’s fuel pump. Monitoring the voltage, the module sustains optimum fuel pressure and fuel flow to the engine over its entire operating range.

The Powertrain Control Module (PCM) monitors the FPM (Fuel Pump Monitor) circuit from the Fuel Pump Driver Module (FPDM). The key on the FPDM continuously provides a duty cycle signal to the Powertrain Control Module via the FPM circuit. In the event that the PCM stops receiving the duty cycle signal, the test fails and the P1234 OBDII diagnostic code will be set.

Symptoms of fault code P1234

  • Check Engine light illuminated.
  • Difficulty starting the engine.
  • Poor acceleration.

Causes of OBD2 P1234

The reasons for the P1234 OBD2 fault code are as follows:

  • Inertia Fuel Shut Off (IFS) switch may require a reset.
  • Fuel Pump Controller Module wiring or electrical connections may be faulty.
  • The IFS switch may be in poor condition.
  • The FPDM may have been damaged.
  • Powertrain Control Module may have deficiencies.

Possible solutions of the DTC code P1234

The corresponding steps to troubleshoot the DTC P1234 OBDII code are:

  • Consult the Technical Service Bulletins.
  • Using an automotive scanner you must verify if additional DTCs to P1234 are configured. If so, diagnose those codes first.
  • Check and test the condition of the Fuel Pump Controller Module circuit wires and the Inertia Fuel Shut-Off If you discover damage from corrosion, wear, or burns, make appropriate repairs.
  • Take electrical readings of the FPDM circuit and compare those results to the manufacturer's specifications. If you detect an out-of-range value, make appropriate repairs.

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