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:
- Fuel Pump Driver Module (FPDM).
- Inertia Fuel Shutoff (IFS) switch.
- Wiring harness circuits (B+, FP, FPM, Ground, FP and VPWR).
- 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 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 circuit 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 and ground terminal at FPDM wiring harness connector. 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 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 8).NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 6). No test procedures have been omitted. - 6) Check Battery Voltage To CCRM
Turn ignition off. Disconnect CCRM connector, located in left front of engine compartment. Measure voltage between terminal No. 11 at CCRM wiring harness connector and ground. 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 B+ circuit. - 7) Check For Open 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: FPDM power supply relay is also referred to as fuel pump relay. - 8) Check B+ Voltage To FPDM Power Supply Relay
Disconnect FPDM power supply relay. Relay is located in power distribution box in engine compartment. Measure voltage between B+ terminal at FPDM power supply relay wiring harness connector and ground. 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 B+ circuit. - 9) Check Ground Circuit
Disconnect scan tool. Measure resistance of ground circuit between negative battery terminal and ground terminal at FPDM power supply relay wiring harness connector. If resistance is 5 ohms or more, repair open ground circuit to FPDM. If resistance is less than 5 ohms, go to next step. - 10) Check For Open FPDM PWR Circuit
Measure resistance of FPDM PWR circuit between FPDM wiring harness connector and FPDM power supply relay wiring harness connector. If resistance is 5 ohms or more, go to step 13). If resistance is less than 5 ohms, reconnect FPDM and go to next step. - 11) Check VPWR Circuit
Turn ignition on. Measure voltage between negative battery terminal and VPWR terminal at FPDM power supply relay wiring harness connector. If voltage more than 10.5 volts, replace FPDM power supply relay. If voltage is 10.5 volts or less, repair open in VPWR circuit.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. - 13) Isolate Open In FPDM PWR Circuit
Turn ignition off. Leave FPDM and FPDM power supply relay disconnected. Disconnect IFS switch. Measure resistance of FPDM PWR circuit between FPDM wiring harness connector and IFS switch wiring harness connector. Also, measure resistance of FPDM PWR circuit between FPDM power supply relay 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 5 ohms or more, repair open in appropriate circuit. - 14) Isolate Open In VPWR Circuit
Turn ignition off. Disconnect EEC-V power relay. Disconnect IFS switch. Measure resistance of VPWR circuit between EEC-V 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. Install Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pin No. 40 (FPM) at breakout box 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 test pin No. 40 at breakout box 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 test pin No. 40 at breakout box 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. Turn ignition on. Measure voltage between test pins No. 40 and 51 (PWR GND) at breakout box. 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 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 changes to less than 20 percent or changes to more than 80 percent.- Wiggle and bend all FPDM system related wiring harnesses and connectors.
- Light tap on FPDM power relay to simulate road shock.
- Lightly tap on IFS switch 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 CIRCUIT 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 40). - 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. Install Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pin No. 80 (FP) at breakout box and FP 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 FP circuit. - 32) Check FP Circuit For Short To Power
Turn ignition on. Measure voltage between test pin No. 80 (FP) at breakout box 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 test pin No. 80 and at breakout box 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 test pins No. 51 (PWR GND) and 80 at breakout box. 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 40). No test procedures have been omitted. - 40) 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 CIRCUIT TEST Z .NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 40) 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 62). 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 FUEL PUMP GROUND terminal at FPDM wiring harness connector. 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 FUEL PUMP GROUND 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 FUEL PUMP GROUND 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 on command did not time-out before voltage check was made. If battery is okay and on command 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 FUEL PUMP GROUND 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 faults are present. 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 FUEL PUMP GROUND 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 CIRCUIT 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) Fuel Pump Always On
Turn ignition on. Using scan tool, select FPM PID from PID/DATA monitor menu. If PID value is 20-30 percent, a FP circuit fault exists. Go to step 31). If PID value is not 20-30 percent, go to next step. - 61) Check Voltage To FPDM With Ignition Off
Turn ignition off. Disconnect FPDM connector. Measure voltage between FPDM PWR terminal at FPDM wiring harness connector and chassis ground. If voltage is 2 volts or less, go to next step. If voltage is more than 2 volts, go to step 65). - 62) Check FPDM
Leave FPDM disconnected. Turn ignition on. Listen for fuel pump operation. If fuel pump operates, repair short to power in FP PWR circuit. If fuel pump does not operate, replace FPDM.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 62) to step 65). No test procedures have been omitted. - 65) Check Voltage To FPDM
Turn ignition off. Disconnect FPDM power supply relay. Measure voltage between FPDM PWR terminal at FPDM wiring harness connector and chassis ground. If voltage is 2 volts or less, replace FPDM power supply relay. If voltage is more than 2 volts, repair short to power in FPDM PWR circuit.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 65) 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, command 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. If voltage is 10.5 volts or less, 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 at FPDM wiring harness connector. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts, or less, go to next step. - 73) Check FP PWR Circuit
Turn ignition off. Connect a jumper wire between FPDM PWR terminal 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:- Disconnect FPDM power supply relay. Relay is located in power distribution box in engine compartment.
Turn ignition on. Measure voltage between B+ terminal at FPDM power supply 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 FPDM power supply relay and repair as necessary.
- 76) Check FPDM PWR Circuit
Turn ignition off and proceed as follows:- Connect a jumper wire between B+ terminal and FPDM PWR terminal at FPDM power supply relay harness connector.
Turn ignition on. Measure voltage between negative battery terminal and FPDM PWR 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.