Diagnostic Aids

Perform this test when instructed during QUICK TEST or if directed by other test procedures. This test is used to diagnose the following:

• Faulty Fuel Pump Driver Module (FPDM)
• Wiring Harness Circuits (B+, GND & VPWR To Fuel Pump Relay; FP, FPM, FP PWR, FP RTN & FPDM PWR).
• Faulty Inertia Fuel Shutoff (IFS) Switch
• Faulty Fuel Pump Relay
• Faulty Powertrain Control Module (PCM)

1. 1) DTC P1233 Or P1234: Check For KOEO DTCs P1233 Or P1234
   
   These DTCs indicate PCM has stopped receiving duty cycle signal from Fuel Pump Driver Module (FPDM). Possible causes are:
   • Inertia Fuel Shutoff (IFS) Switch Needs To Be Reset
   • Open FPDM Ground Circuit
   • Open Or Shorted FPM Circuit
   • Faulty IFS Switch
   • Faulty FPDM
   • Faulty PCM

   If DTC P1233 or P1234 is present in KOEO ON-DEMAND SELF-TEST, go to next step. If DTC P1233 or P1234 is not present in KOEO ON-DEMAND SELF-TEST, PCM is now receiving a signal from FPDM. Fault code may have been set due to Inertia Fuel Shutoff (IFS) switch being tripped, then reset. If engine starts, go to step  25). If engine is a no-start, disregard DTCs P1233 and P1234 at this time and repeat QUICK TEST . If any other DTCs are present, perform appropriate system test and repair as necessary. After repairing the engine no-start condition, go to step  25) to diagnose intermittent causes of DTC P1233 or P1234.

2. 2) Check If Engine Starts
   
   Attempt to start engine. If engine starts, go to step  15). If engine does not start, verify IFS switch is set (button depressed) and go to next step.
3. 3) Check Power & Ground Circuits To FPDM
   
   Turn ignition switch to OFF position. Disconnect FPDM connector. Turn ignition switch to ON position. Using a DVOM, measure voltage between FPDM harness connector FPDM PWR circuit terminal (VPWR circuit terminal on Continental) and ground circuit terminal. FPDM PWR or VPWR is the power circuit coming from the IFS switch to the FPDM. If voltage is more than 10.5 volts, replace FPDM. If voltage is 10.5 volts or less, go to next step.
4. 4) Check Power To FPDM
   
   Turn ignition switch to ON position. Using a DVOM, measure voltage between ground and FPDM harness connector FPDM PWR circuit terminal. If voltage is more than 10.5 volts, repair open ground circuit to FPDM. If voltage is 10.5 volts or less, go to next step.
   Fig 1: Identifying ISO Micro Relay Cavity Terminals

   Courtesy of FORD MOTOR CO.
5. 9) Check For Ground To Fuel Pump Relay
   
   Turn ignition switch to OFF position. Disconnect scan tool from DLC. Using a DVOM, measure resistance of ground circuit between fuel pump relay cavity No. 2 in battery junction box and negative battery terminal. See Fig 1. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in ground circuit.
6. 10) Check For Open FPDM PWR Circuit
   
   Using a DVOM, measure resistance of FPDM power circuit between fuel pump relay cavity No. 5 and FPDM harness connector terminal No. 9. See Fig 1 and Fig 2 . If resistance is less than 5 ohms, reconnect FPDM and go to next step. If resistance is 5 ohms or more, FPDM circuit circuit is open. Go to step  13) to isolate fault.
   Fig 2: Identifying Fuel Pump Driver Module Connector Terminals

   Courtesy of FORD MOTOR CO.
7. 11) Check VPWR Circuit Voltage To Fuel Pump Relay
   
   Turn ignition switch to ON position. Using a DVOM, measure VPWR circuit voltage between ground and fuel pump relay cavity No. 1. See Fig 1. If voltage is more than 10.5 volts, replace fuel pump relay. If voltage is 10.5 volts or less, repair open in VPWR circuit. See WIRING DIAGRAMS article.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 11) to step 13). No test procedures have been omitted.
8. 13) Isolate Open In FPDM PWR Circuit
   
   Disconnect Inertia Fuel Shutoff (IFS) switch connector. Measure resistance of FPDM PWR circuit between FPDM harness connector terminal No. 9 and IFS switch harness connector. See Fig 2. If both resistance measurements are less than 5 ohms, verify IFS switch is set (button depressed). If IFS switch is set, replace IFS switch. If either resistance measurement is 5 ohms or more, repair open in appropriate FPDM PWR circuit.
   NOTE: PCM power relay is also referred to as EEC-V power relay.
9. 14) Check For Open FPM Circuit
   
   Turn ignition switch to OFF position. Disconnect FPDM connector. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance of FPM circuit between PCM harness connector terminal No. 40 and FPDM harness connector terminal No. 7. See Fig 2. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in FPM circuit.
10. 15) Check FPM Circuit For Short To VPWR In Harness
    
    Turn ignition switch to ON position. Using a DVOM, measure voltage between PCM harness connector terminal No. 40 and ground. If voltage is less than one volt, go to next step. If voltage is one volt or more, repair short to VPWR in FPM circuit.
11. 16) Check FPM Circuit For Short To Ground In Harness
    
    Turn ignition switch to OFF position. Disconnect scan tool from Data Link Connector (DLC). Using a DVOM, measure resistance between PCM harness connector terminal No. 40 and ground. If resistance is more than 10 k/ohms, go to next step. If resistance is 10 k/ohms or less, repair short to ground in FPM circuit.
NOTE: In the following test step, it is normal for voltage to cycle less than .02 volt and return to .02-1.0 volt.