Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 26 other vehicles, including the 1999 Mercury Tracer, 1999 Mercury Sable, 1999 Mercury Mystique, 1999 Mercury Mountaineer, and 1999 Mercury Grand Marquis. However, it is still accessible from the selected car via links, so may be relevant.
Perform this test when instructed during QUICK TEST or if directed by other test procedures. This test is used to diagnose the following:
- Fuel Pump Driver Module (FPDM).
- Inertia Fuel Shutoff (IFS) switch.
- Wiring harness circuits (B+, FP, FPM, Ground, FP and VPWR). See Fig 1-Fig 3 .
- FPDM power supply relay.
- Powertrain Control Module (PCM).
- 1) DTC P1233 Or P1234
These DTCs indicate PCM has stopped receiving diagnostic information from Fuel Pump Driver Module (FPDM). 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 may have been Inertia Fuel Shutoff (IFS) switch was tripped, then reset. If engine starts, go to step 25). If vehicle has a no-start condition, 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 no-start condition, go to step 25) to diagnose intermittent causes of DTC P1233 or P1234. - 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) Check Power & Ground Circuits To FPDM
Turn ignition off. Disconnect FPDM connector. Turn ignition on. Measure voltage between FPDM PWR terminal (VPWR terminal on Continental) and ground terminal at FPDM wiring harness connector. 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) Check Power To FPDM
Turn ignition on. Measure voltage between FPDM PWR terminal (VPWR terminal on Continental) at FPDM wiring harness connector and ground. If voltage is more than 10.5 volts, repair open ground circuit to FPDM. If voltage is 10.5 volts or less, go to step 14) (Continental) or go to next step (Escort, Mustang and Tracer). - 5) Check Battery Voltage To CCRM (Escort, Mustang & Tracer)
Turn ignition off. Disconnect CCRM connector. On Mustang, CCRM is mounted on a bracket behind engine coolant reservoir. On Escort and Tracer, CCRM is located in left front of engine compartment. On all models, measure voltage between terminal No. 11 at CCRM wiring harness connector and ground. See Fig 4. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, check condition of related fuse. If fuse is blown, check for short to ground. Repair as necessary. If fuse is okay, repair open in B+ circuit. - 6) Check For Open Ground Circuit
Measure resistance of ground circuit between terminal No. 18 at CCRM wiring harness connector and chassis ground. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in ground circuit. - 7) Check For Open FPDM PWR Circuit
Measure resistance of FPDM PWR circuit between terminal No. 5 at CCRM wiring harness connector and FPDM wiring harness connector. If resistance is less than 5 ohms, replace CCRM. If resistance is 5 ohms or more, go to step 13).NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 7) to step 13). No test procedures have been omitted. - 13) Isolate Open Circuit
Disconnect Inertia Fuel Shutoff (IFS) switch connector. Measure resistance of FPDM PWR circuit between IFS switch wiring harness connector and FPDM power relay wiring harness connector. Also measure resistance of FPDM PWR connector between FPDM wiring harness connector and IFS switch wiring harness connector. If both resistance readings are less than 5 ohms, verify IFS switch is set (button depressed). If IFS switch is set, replace IFS switch. If any resistance reading is 5 ohms or more, repair open in FPDM circuit. - 14) Isolate Open In VPWR Circuit
Turn ignition off. Disconnect PCM power relay. Disconnect Inertia Fuel Shutoff (IFS) switch. Measure resistance of VPWR circuit between PCM power relay wiring harness connector and IFS switch wiring harness connector. Also measure resistance of VPWR circuit between FPDM wiring harness connector and IFS switch wiring harness connector. If both resistance readings are less than 5 ohms, verify IFS switch is set (button depressed). If IFS switch is set, replace IFS switch. If resistance is more than 5 ohms, repair open in VPWR circuit. - 15) Check For Open FPM Circuit
Turn ignition off. Disconnect FPDM connector. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector pin No. 40 (FPM) and FPM terminal at FPDM wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in FPM circuit. - 16) Check For Short To Power
Turn ignition on. Measure voltage between PCM connector pin 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 power in FPM circuit. - 17) Check FPM For Short To Ground
Turn ignition off. Disconnect scan tool. Measure resistance between PCM connector pin No. 40 and ground. If resistance is more than 10,000 ohms, go to next step. If resistance is 10,000 ohms or less, repair short to ground in FPM. - 18) Check FPM Output From FPDM
Reconnect FPDM connector. Turn ignition on. Measure voltage between PCM connector pin No. 40 and ground. If voltage is .2-1.0 volt, replace PCM. If voltage is not .2-1.0 volt, replace FPDM. It is normal for voltage to cycle less than .02 volt and return to .02-1.0 volt.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 18) to step 25). No test procedures have been omitted. - 25) Check For Intermittent Short Or Open Circuit
Turn ignition on. Using scan tool, select FP M PID from PID/DATA monitor menu. Observe FP M PID value for indication of fault while performing the following. Fault will be indicated if FP M PID value changes to less than 20 percent or changes to more than 80 percent:- Wiggle and bend all FPDM system related wiring harnesses and connectors.
- On Escort, Mustang and Tracer, wiggle and bend B+ circuit to terminal No. 11 at CCRM.
- On Mustang, wiggle and bend ground circuit to terminal No. 18 at CCRM.
- On all models, wiggle and bend FPM circuit between PCM and FPDM.
- Lightly tap on IFS switch, CCRM and FPDM to simulate road shock.
If any faults are found, isolate fault and repair as necessary. If no faults are found, problem cannot be duplicated at this time. Go to TEST Z .
NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 25) to step 30). No test procedures have been omitted. - 30) DTC P1235 Or P1236
These DTCs indicate an FP circuit fault has been detected. This is due to an intermittent or hard fault. If DTC P1235 or P1236 is present in KOEO ON-DEMAND SELF-TEST or KOER ON-DEMAND SELF-TEST, DTC is a hard fault. Go to next step. If DTC P1235 or P1236 is not present in KOEO ON-DEMAND SELF-TEST or KOER ON-DEMAND SELF-TEST, fault is intermittent. Go to step 45). - 31) Check For Open Circuit
Turn ignition off. Disconnect FPDM connector. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector pin No. 80 (FP) and FP terminal at FPDM wiring harness connector. See Fig 1-Fig 3 . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in FP circuit. - 32) Check FP Circuit For Short To Power
Turn ignition on. Measure voltage between PCM connector pin No. 80 (FP) and ground. If voltage is less than one volt, go to next step. If voltage is one volt or more, repair short to power in FP circuit. - 33) Check For Short To Ground
Turn ignition off. Disconnect scan tool. Measure resistance between PCM connector pin No. 80 and ground. If resistance is more than 10,000 ohms, go to next step. If resistance is 10,000 ohms or less, repair short to ground in FP circuit. - 34) Check FP Circuit In FPDM
Reconnect FPDM. Turn ignition on. Measure voltage between PCM connector pins No. 51 (PWR GND) and 80. If voltage is 4.5-5.5 volts, replace PCM. If voltage is not 4.5-5.5 volts, replace FPDM.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 34) to step 45). No test procedures have been omitted. - 45) Check For Intermittent Short Or Open Circuit
Turn ignition on. Using scan tool, select FP M PID. Observe FP M PID value for indication of fault while lightly tapping on FPDM to simulate road shock. Fault will be indicated if FP M PID value changes from 50 percent. Wiggle and bend FP circuit between FPDM and PCM. If any faults are found, isolate fault and repair as necessary. If no faults are found, problem cannot be duplicated at this time. Go to TEST Z .NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 45) to step 47). No test procedures have been omitted. - 47) DTC P1237 Or P1238
These DTCs indicate FPDM has detected a fuel pump secondary circuit fault. This is due to an intermittent or hard fault. If DTC P1237 or P1238 is present in KOEO ON-DEMAND SELF-TEST or KOER ON-DEMAND SELF-TEST, DTC is a hard fault. Go to next step. If DTC P1237 or P1238 is not present in KOEO or KOER ON-DEMAND SELF-TEST, fault is intermittent. Go to step 57). - 48) Check If Engine Starts
Attempt to start engine. If engine starts, go to step 60). If engine does not start, go to next step. - 49) Check Circuit Resistance
Turn ignition off. Disconnect scan tool. Disconnect FPDM connector. Measure resistance between FP PWR terminal and FP RTN terminal at FPDM wiring harness connector. See Fig 1-Fig 3 . If resistance is 10 ohms or more, go to step 54). If resistance is less than 10 ohms, go to next step. - 50) Check Ground Circuit For Short To Power
Turn ignition on. Measure voltage between chassis ground and FP RTN terminal at FPDM wiring harness connector. If voltage is one volt or more, repair short to power. If voltage is less than one volt, go to next step. - 51) Check FP PWR Circuit For Short To Ground
Turn ignition off. Disconnect fuel pump connector. Measure resistance between negative battery terminal and FP PWR terminal at FPDM wiring harness connector. If resistance is more than 10,000 ohms, go to next step. If resistance is 10,000 ohms or less, repair short to ground in FP PWR circuit. - 52) Check For Power To Fuel Pump
Reconnect FPDM and scan tool. Turn ignition on. Connect DVOM between FP PWR terminal and FP RTN terminal at fuel pump wiring harness connector. Using scan tool, access OUTPUT TEST MODE. Command fuel pump ON. Fuel pump will turn on for about 5 seconds. With fuel pump commanded on, if voltage is more than 10 volts, replace fuel pump. If voltage is 10 volts or less, verify battery is full charged. Ensure fuel pump command on time did not time-out before voltage check was made. If battery is okay and command on time did not time-out, replace FPDM.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 52) to step 54). No test procedures have been omitted. - 54) Isolate Open Circuit
Turn ignition off. Disconnect fuel pump. Measure resistance of FP PWR circuit between fuel pump wiring harness connector and FPDM wiring harness connector. Measure resistance of FP RTN circuit between fuel pump wiring harness connector and FPDM wiring harness connector. Also measure internal resistance of fuel pump. If all resistance readings are less than 10 ohms, no fault is detected at this time. Verify results of previous steps. If any resistance reading is 10 ohms or more, repair open in appropriate circuit or replace fuel pump.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 54) to step 57). No test procedures have been omitted. - 57) Check Fuel Pump Secondary Circuit
Turn ignition on. Using scan tool, select FP M PID. Observe FP M PID value for indication of fault while lightly tapping on FPDM to simulate road shock. Fault will be indicated if FP M PID value changes from 50 percent. Wiggle and bend FP PWR circuit and FP RTN circuit between FPDM and fuel pump. Lightly tap on fuel pump and FPDM to simulate road shock. If any faults are found, isolate fault and repair as necessary. If no faults are found, go to next step. - 58) Check FP PWR Circuit For Short To Ground
Turn ignition off. Disconnect FPDM. Connect a test light between FP PWR terminal and FPDM PWR terminal at FPDM wiring harness connector. Turn ignition on. Observe test light for indication of fault while wiggling and bending FP PWR circuit between FPDM and fuel pump. If a fault is indicated, test light will turn on. If any faults are found, isolate fault and repair as necessary. If no faults are found, unable to duplicate or identify fault at this time. Go to TEST Z .NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 58) to step 60). No test procedures have been omitted. - 60) Check For Short To Ground In FP RTN Circuit
Turn ignition off. Disconnect FPDM connector. Turn ignition on. Measure voltage between FPDM PWR terminal (VPWR terminal on Continental) and FP RTN terminal at FPDM wiring harness connector. If voltage is less than one volt, replace FPDM. If voltage is one volt or more, repair short to ground in FP RTN circuit.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 60) to step 70). No test procedures have been omitted. - 70) Check Battery Voltage With Outputs Commanded On
Turn ignition off. Disconnect fuel pump connector. Connect scan tool to DLC. Turn ignition on. Using scan tool, access OUTPUT TEST MODE. Connect a DVOM between battery terminals. While monitoring battery voltage, turn all outputs on. If battery voltage is more than 11 volts, command all outputs OFF and go to next step. If battery voltage is 11 volts or less, service battery/charging system as necessary. - 71) Check Ground Circuit To Fuel Pump
Turn ignition off. Connect DVOM between FP PWR terminal at fuel pump wiring harness connector and negative battery terminal. Using scan tool, command all outputs ON. Note voltage reading within 5 seconds. If voltage is 10.5 volts or less, ground circuit is okay. Go to next step. If voltage is more than 10.5 volts, locate and repair fault in ground circuit to fuel pump. - 72) Check Voltage To FPDM
Turn ignition off. Disconnect FPDM connector. Turn ignition on. Measure voltage between negative battery terminal and FPDM PWR terminal (VPWR terminal on Continental) at FPDM wiring harness connector. See Fig 1-Fig 3 . If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts, or less, go to step 75). - 73) Check FP PWR Circuit
Turn ignition off. Connect a jumper wire between FPDM PWR terminal (VPWR terminal on Continental) and FP PWR terminal at FPDM wiring harness connector. Turn ignition on. Measure voltage between FP PWR terminal at fuel pump wiring harness and negative battery terminal. If voltage is more than 10.5 volts, and is within .5 volt of voltage measured in step 72) , replace FPDM. If voltage is not as specified, isolate high resistance in FP PWR circuit and repair as necessary.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 73) to step 75). No test procedures have been omitted. - 75) Check For B+
Turn ignition off and proceed as follows:- On Continental, disconnect PCM power relay. Relay is located in power distribution box in left side of engine compartment, above wheelwell. Turn ignition on. Measure voltage between B+ terminal at PCM power relay wiring harness connector and negative battery terminal. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, check for incorrect voltage supply to PCM power relay and repair as necessary.
- On Escort, Mustang and Tracer, disconnect Constant Control Relay Module (CCRM). On Mustang, CCRM is mounted on a bracket behind engine coolant reservoir. On Escort and Tracer, CCRM is located in left front of engine compartment. On all models, turn ignition on. Measure voltage between terminal No. 11 at CCRM wiring harness connector and negative battery terminal. See Fig 4. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, check for incorrect voltage supply to CCRM and repair as necessary.
- 76) Check FPDM PWR Circuit
Turn ignition off and proceed as follows:- On Continental, connect a jumper wire between B+ terminal and VPWR terminal at PCM power relay harness connector. Turn ignition on. Measure voltage between negative battery terminal and VPWR terminal at FPDM wiring harness connector. If voltage is more than 10.5 volts, replace FPDM. If voltage is 10.5 volts or less, isolate for high resistance in system circuits and repair as necessary.
- On Escort, Mustang and Tracer, connect a jumper wire between terminals No. 11 (B+) and No. 5 (FPDM PWR) at CCRM wiring harness connector. Turn ignition on. Measure voltage between negative battery terminal and FPDM terminal at FPDM wiring harness connector. If voltage is more than 10.5 volts, replace FPDM. If voltage is 10.5 volts or less, isolate for high resistance in system circuits and repair as necessary.
NOTE:
PCM power relay is also referred to as EEC-V power relay.