Ford Mustang Forums
 Home Register FAQ New Posts Members List Contact Us     Log In Log In  
 
Ford Mustang Forums Tech Related Engine & Performance V6 Guys

v6 fuel issues, heres a checklist. good info

asohagan 24.01.2012, 22:55
while chasing a wiring gremlin i recently found this. its really good info and walks you through every step


The codes you have are as follows,

P1233--fuel pump driver module disabled/offline

P1235--fuel pump control outof range

P0190--fuel rail pressure sensor circuit malfunction

we will start with the P1233 since it is there steady.

Here is the pinpoint test to follow,

The fuel pump driver module is located in the trunk on the left side. It most likely is the driver module.


--------------------------------------------------------------------------------


KB: Fuel Pump Driver Module (FPDM) KB: Introduction



--------------------------------------------------------------------------------


KB1 DTC P1233 OR P1234: IS DTC P1233 OR P1234 PRESENT IN KEY ON ENGINE OFF SELF TEST
Is DTC P1233 or P1234 present in Key On Engine Off Self-Test?

Yes No
A hard fault is present. GO to KB2 . The PCM is now receiving a signal from the FPDM. One possible cause of the DTC P1233 or P1234 is that the IFS switch was tripped, then reset.

If engine is now a no start:

Disregard the DTC P1233 or P1234 at this time. RETURN to Section 3 and CONTINUE as directed. After servicing the no start, to diagnose intermittent causes of the DTC P1233 or P1234, RETURN to GO to KB25 .

If engine will start:

GO to KB25 to diagnose intermittent condition.

KB2 DOES THE ENGINE START?
Does the engine start?

Yes No
GO to KB15 (to check the FPM circuit). VERIFY IFS switch is set (button depressed). If OK, GO to KB3 .

KB3 CHECK POWER AND GROUND CIRCUITS TO FPDM
Disconnect FPDM.
Key on, engine off.
Measure voltage between the FPDM PWR pin and ground pin at the FPDM harness connector.
Is voltage greater than 10.5 volts?






Yes No
Key off. REPLACE FPDM. GO to KB4 .

KB4 CHECK POWER TO FPDM
Key on, engine off.
Measure voltage between the FPDM PWR pin at the FPDM harness connector and chassis ground.
Is voltage greater than 10.5 volts?




Yes No
REPAIR open ground circuit to FPDM. KEY OFF. No power to FPDM.

For Escort, Mustang:

GO to KB5 .

All Others:

GO to KB8 .

KB5 CHECK B+ VOLTAGE TO CCRM PIN 11 (FPDM POWER SUPPLY RELAY)
Disconnect CCRM.
Measure B+ circuit voltage at Pin 11 of the CCRM harness connector.
Is voltage greater than 10.5 volts?

Yes No
For Mustang:

GO to KB6 .

For Escort:

GO to KB7 . VERIFY integrity of related fuse. If OK, REPAIR open B+ circuit. If fuse is damaged, CHECK B+ and FPDM PWR circuits for short to ground before replacing.

KB6 CHECK GROUND CIRCUIT TO CCRM PIN 18
Measure resistance of ground circuit between CCRM harness connector Pin 18 and chassis ground.
Is resistance less than 5.0 ohms?

Yes No
GO to KB7 . SERVICE open ground circuit.

KB7 CHECK FOR OPEN FPDM PWR CIRCUIT
Measure resistance of FPDM PWR circuit between CCRM harness connector (pin 5) and FPDM harness connector.
Is resistance less than 5.0 ohms?

Yes No
REPLACE CCRM. The FPDM PWR circuit is open. GO to KB13 to help isolate fault.

KB8 CHECK B+ VOLTAGE TO FPDM POWER SUPPLY RELAY
Disconnect FPDM power supply relay.
Measure B+ circuit voltage at the FPDM power supply relay harness connector.
Is voltage greater than 10.5 volts?

Yes No
GO to KB9 . VERIFY integrity of related fuse. If OK, REPAIR open B+ circuit. If fuse is damaged, CHECK B+ and FPDM PWR circuits for short to ground before replacing.

KB9 CHECK FOR GROUND TO FPDM POWER SUPPLY RELAY
Disconnect scan tool from DLC.
Measure resistance of ground circuit between FPDM power supply relay harness connector and battery negative post.
Is resistance less than 5.0 ohms?

Yes No
GO to KB10 . REPAIR open circuit.

KB10 CHECK FOR OPEN FPDM PWR CIRCUIT
Measure resistance of FPDM PWR circuit between FPDM power supply relay harness connector and FPDM harness connector.
Is resistance less than 5.0 ohms?

Yes No
RECONNECT FPDM. GO to KB11 . The FPDM PWR circuit is open. GO to KB13 to help isolate fault.

KB11 CHECK VPWR CIRCUIT VOLTAGE (IGN START/RUN for Taurus/Sable) TO FPDM POWER SUPPLY RELAY
Key on, engine off.
Measure VPWR circuit voltage (IGN START/RUN for Taurus/Sable) at the FPDM power supply relay harness connector.
Is voltage greater than 10.5 volts?

Yes No
REPLACE FPDM power supply relay. REPAIR open VPWR (or IGN START/RUN) circuit.

KB13 ISOLATE OPEN IN FPDM PWR CIRCUIT
Disconnect IFS switch.
Measure resistance of FPDM PWR circuit between IFS switch harness connector and FPDM power supply relay harness connector (for Escort and Mustang, CCRM harness connector [pin 5]).
Measure resistance of FPDM PWR circuit between FPDM harness connector and IFS switch harness connector.
Are both resistances less than 5.0 ohms?

Yes No
VERIFY that the IFS switch is set (button depressed). If OK, REPLACE IFS switch. REPAIR open in appropriate area of FPDM PWR circuit.

KB15 CHECK FOR OPEN FPM CIRCUIT
Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

Disconnect FPDM.
Disconnect PCM.
Measure resistance of FPM circuit between PCM harness connector and the FPDM harness connector.
Is resistance less than 5.0 ohms?

Yes No
GO to KB16 . REPAIR open circuit.

KB16 CHECK FPM CIRCUIT FOR SHORT TO POWER IN HARNESS
Key on, engine off.
Measure voltage between FPM circuit at the PCM harness connector and ground.
Is voltage less than 1.0 volt?

Yes No
KEY OFF. GO to KB17 . REPAIR short circuit.

KB17 CHECK FPM CIRCUIT FOR SHORT TO GROUND IN HARNESS
Disconnect scan tool from DLC.
Measure resistance between FPM circuit at the PCM harness connector and ground.
Is resistance greater than 10,000 ohms?

Yes No
GO to KB18 . REPAIR short circuit.

KB18 CHECK FOR FPM OUTPUT FROM FPDM
Reconnect FPDM.
Key on, engine off.
Measure dc voltage between FPM circuit at the PCM harness connector and ground.
Is voltage between 0.02 and 1.0 volt dc? (It is OK for the voltage to cycle below this range and then return to within range.)

Yes No
REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ). REPLACE FPDM.

KB25 CHECK CIRCUITS THAT MAY CAUSE AN INTERMITTENT LOSS OF POWER SUPPLY TO THE FPDM. ALSO CHECK FOR INTERMITTENT OPENS OR SHORTS ON THE FPM CIRCUIT.
Note: Be aware that P1233/1234 could be set if the inertia fuel shutoff (IFS) switch was tripped then reset.

Key on, engine off.
Access FPM PID.
Note: With no fault detected, the FPDM will send a 50% duty cycle signal (all OK) to the PCM on the FPM circuit. Depending on scan tools, the FPM PID may display 50%, or a random value that is fluctuating between 85 and 115%.

Observe FPM PID for an indication of a fault while completing the following (look for the FPM PID to change from the 50% value, or to stop fluctuating):
Shake, wiggle, bend the following circuits:
FPDM ground.
FPDM PWR circuit to FPDM.
For Escort and Mustang, the B+ circuit to CCRM pin 11. For Mustang, also the ground circuit to CCRM Pin 18.
For all except Escort and Mustang, the B+ and ground circuits to FPDM power supply relay.
FPM circuit between the FPDM and the PCM.
Lightly tap on the IFS Switch, FPDM and CCRM or FPDM power supply relay to simulate road shock.
Key off.
Is a fault indicated?

Yes No
ISOLATE fault and REPAIR as necessary. Unable to duplicate or identify fault at this time. GO to Z1 .

KB30 DTC P1235 OR P1236: IS DTC P1235 OR P1236 PRESENT IN KEY ON ENGINE OFF OR ENGINE RUNNING SELF TEST?
Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

Note: For LS6/LS8 and Thunderbird, the FPDM functions are incorporated in the Rear Electronics Module (REM). In the following steps, if directed to perform an action with the FPDM, complete the action with the REM. Refer to the pin numbers in the beginning of this pinpoint test.

Is DTC P1235 or P1236 present in Key On Engine Off or Engine Running Self-Test?

Yes No
A hard fault is present. GO to KB31 to check the FP circuit. DTC P1235 or P1236 is intermittent.

For LS6/LS8 and Thunderbird :

GO to KB42 .

All others :

GO to KB45 .

KB31 CHECK FOR OPEN FP CIRCUIT BETWEEN PCM AND FPDM
Disconnect FPDM.
Disconnect PCM.
Measure resistance of FP circuit between PCM harness connector pin and the FPDM harness connector.
Is resistance less than 5.0 ohms?

Yes No
GO to KB32 . REPAIR open circuit.

KB32 CHECK FP CIRCUIT FOR SHORT TO POWER IN HARNESS
Key on, engine off.
Measure voltage between FP circuit at PCM harness connector pin and ground.
Is voltage less than 1.0 volt?

Yes No
KEY OFF. GO to KB33 . REPAIR short circuit.

KB33 CHECK FP CIRCUIT FOR SHORT TO GROUND IN HARNESS
Disconnect scan tool from DLC.
Measure resistance between FP circuit at PCM harness connector pin and ground.
Is resistance greater than 10,000 ohms?

Yes No
For LS6/LS8 and Thunderbird :

GO to KB36 .

All others :

GO to KB34 . REPAIR short circuit.

KB34 CHECK FP CIRCUIT IN FPDM
Reconnect FPDM.
Key on, engine off.
Measure voltage between FP circuit at PCM harness connector pin and ground.
Is voltage between 4.5 and 5.5 volts?

Yes No
REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ). REPLACE FPDM.

KB36 CHECK FPF PID
Key on, engine off.
Access the FP and FPF PIDs on the scan tool (the FP PID may be used in the next step).
While viewing the FPF PID for 20 seconds, check if the FPF PID will indicate YES. The FPF PID may read NO in the 20 seconds, but will change back to YES.
Does the FPF PID indicate YES within 20 seconds?

Yes No
GO to KB40 . GO to KB37 .

KB37 CHECK FP PID
Does the FP PID indicate between 70 and 80%?

Yes No
GO to KB38 . TURN KEY OFF then back ON. Wait 5 seconds. REPEAT test step. If result is now YES, follow YES result. If result is still NO, REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ).

KB38 ACCESS REM PIDS AND CHECK PWM_DC1 PID
Access the PWM_DC1 PID from the REM menu (the PWM_DC1 PID indicates the signal sent to the REM from the PCM on the FP circuit).
Does the PWM_DC1 PID indicate between 70 and 80%?

Yes No
KEY OFF. No fault indicated. Disregard DTC P1235 or P1236. RETURN to Section 3 where DTC was received and proceed as directed. REPLACE REM.

KB40 CHECK REM CIRCUITRY VOLTAGE ON FP CIRCUIT AT PCM
Key off.
Disconnect PCM connector B (BODY).
Key on, engine off.
Measure voltage between pin B58 at PCM harness connector B and ground.
Is voltage greater than 8 volts?

Yes No
REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ). REPLACE REM.

KB42 CHECK FP CIRCUIT FOR INTERMITTENT CONCERNS
Key on, engine off.
Access the REM PID access menu on the scan tool.
Access the PWM_DC1 PID from the REM menu (the PWM_DC1 PID indicates the signal sent to the REM from the PCM on the FP circuit).
Observe the PWM_DC1 PID for indication of a fault while completing the following (the PID value will change when a fault is detected):
Shake, wiggle and bend the FP circuit between the PCM (Pin B58) and REM (Pin J2-19).
Is a fault indicated?

Yes No
ISOLATE fault and REPAIR as necessary. KEY OFF. Unable to duplicate or identify fault at this time. GO to Z1 with the following data: PWM_DC1 PID (REM menu), FP PID (PCM menu, the FP PID is the signal the PCM is sending to the REM).

KB45 CHECK FP CIRCUIT FOR INTERMITTENT OPENS OR SHORTS
Key on, engine off.
Access FPM PID.
Note: With no fault detected, the FPDM will send a 50% duty cycle signal (all OK) to the PCM on the FPM circuit. Depending on scan tools, the FPM PID may display 50%, or a random value that is fluctuating between 85 and 115%.

Observe the FPM PID for an indication of a fault while completing the following (look for the FPM PID to change from the 50% value, or to stop fluctuating):
Shake, wiggle, bend the FP circuit between FPDM and the PCM.
Lightly tap on the FPDM (to simulate road shock).
Is a fault indicated?

Yes No
ISOLATE fault and REPAIR as necessary. KEY OFF. Unable to duplicate or identify fault at this time.GO to Z1 .

KB47 DTC P1237 OR P1238: IS DTC P1237 OR P1238 PRESENT IN KEY ON ENGINE OFF OR ENGINE RUNNING SELF TEST
Is DTC P1237 or P1238 present in Key On Engine Off or Key On Engine Running Self-Test?

Yes No
A hard fault is present. GO to KB48 . DTC P1237 or P1238 is possibly intermittent.

For LS6/LS8 and Thunderbird :

GO to KB67 .

All others :

GO to KB56 .

KB48 DOES THE ENGINE START?
Does the engine start?

Yes No
For LS6/LS8 and Thunderbird :

GO to KB80 .

All others :

DISCONNECT FPDM. GO to KB59 . For LS6/LS8 and Thunderbird :

GO to KB61 .

All others :

GO to KB49 to check fuel pump secondary circuits.

KB49 CHECK FP PWR, FP RTN AND INTERNAL FUEL PUMP CIRCUIT RESISTANCE
Disconnect scan tool from DLC.
Disconnect FPDM.
Measure resistance between FP PWR circuit and the FP RTN circuit at the FPDM harness connector.
Is resistance less than 10.0 ohms?

Yes No
GO to KB50 . An open secondary circuit exists. GO to KB54 to isolate fault.

KB50 CHECK FP RTN CIRCUIT FOR SHORT TO POWER IN HARNESS
Key on, engine off.
Measure voltage between the FP RTN circuit in harness and chassis ground.
Is voltage less than 1.0 volt?

Yes No
GO to KB51 . REPAIR short circuit.

KB51 CHECK FP PWR CIRCUIT FOR SHORT TO GROUND IN HARNESS
Disconnect fuel pump.
Measure resistance between the FP PWR circuit in harness and ground.
Is resistance greater than 10,000 ohms?

Yes No
GO to KB52 . REPAIR short circuit.

KB52 CHECK FOR VOLTAGE TO FUEL PUMP
Reconnect FPDM.
Reconnect scan tool.
Key on, engine off.
Access Output Test Mode on scan tool. (To complete this test step without a scan tool, the fuel pump can be commanded on for one second by cycling the key from off to on. Repeat as needed.)
Connect digital multimeter between the FP PWR circuit and the FP RTN circuit at the fuel pump harness connector.
While monitoring voltage, command outputs on (this commands the fuel pump on for about 5 seconds).
With the fuel pump commanded on, is the voltage greater than 10.0 volts?

Yes No
REPLACE fuel pump. VERIFY vehicle battery was at proper charge during test. VERIFY pump on command did not time-out before voltage check was made. If OK, REPLACE FPDM.

KB54 ISOLATE OPEN CIRCUIT
Disconnect fuel pump.
Measure resistance of the FP PWR circuit between the FPDM and fuel pump harness connectors.
Measure resistance of the FP RTN circuit between the FPDM and fuel pump harness connectors.
Measure internal resistance of the fuel pump.
Is each resistance less than 10.0 ohms?

Yes No
No fault is detected. VERIFY results of previous test steps. REPAIR open in appropriate circuit (if open was internal to pump, REPLACE fuel pump).

KB56 VERIFY THAT DTC P1237 OR P1238 IS INTERMITTENT
Note: When the FPDM is detecting a secondary fuel pump circuit fault (the wires going to the fuel pump), a 75% duty cycle signal will be sent to the PCM on the FPM circuit. On some scan tools, the FPM PID may display the 75% signal as a random value that is fluctuating between 250 and 400%.

Key on, engine off.
Access FPM PID.
Is the FPM PID 75% (or varying between 250 and 400%)?

Yes No
A hard fault is present. GO to KB48 . DTC P1237 or P1238 is intermittent. GO to KB57 .

KB57 CHECK FUEL PUMP SECONDARY CIRCUITS FOR INTERMITTENT OPEN OR SHORT
Key on, engine off.
Access FPM PID.
Note: With no fault detected, the FPDM will send a 50% duty cycle signal (all OK) to the PCM on the FPM circuit. Depending on scan tools, the FPM PID may display 50%, or a random value that is fluctuating between 85 and 115%.

Observe the FPM PID for an indication of a fault while completing the following (the FPM PID will change from the normal (all OK) reading when a fault is detected):
Shake, wiggle, bend the FP PWR circuit and FP RTN circuit between the FPDM and the fuel pump.
Lightly tap the fuel pump and the FPDM to simulate road shock.
Is a fault indicated?

Yes No
ISOLATE fault and REPAIR as necessary. KEY OFF. GO to KB58 .

KB58 CHECK FP PWR CIRCUIT FOR SHORT TO GROUND
Disconnect FPDM.
Connect a non-powered test lamp between the FP PWR circuit and the FPDM PWR circuit at the FPDM harness connector.
Key on.
Observe test lamp for an indication of a fault while completing the following (the test lamp will turn on when a fault is detected, indicating a short to ground):
Shake, wiggle, bend the FP PWR circuit between the FPDM and the fuel pump.
Is a fault indicated?

Yes No
ISOLATE fault and REPAIR as necessary. KEY OFF. Unable to duplicate or identify fault at this time. RECONNECT FPDM. GO to Z1 .

KB59 CHECK FP PWR CIRCUIT FOR SHORT TO POWER
FPDM disconnected.
Key on, engine off.
Measure voltage between the FP PWR circuit at the FPDM harness connector and chassis ground.
Is voltage less than 1.0 volt?

Yes No
GO to KB60 . REPAIR FP PWR circuit short to power.

KB60 CHECK FP RTN CIRCUIT FOR SHORT TO GROUND
FPDM disconnected.
Key on.
Measure voltage between the FPDM PWR and FP RTN circuits at the FPDM harness connector.
Is voltage less than 1.0 volt?

Yes No
REPLACE FPDM. REPAIR FP RTN circuit short to ground.

KB61 CHECK REM/FP PWR AND GROUND CIRCUIT TO REM PINS J1-1, J1-2
Note: Verify inertia fuel shutoff (IFS) switch is not tripped.

Disconnect REM connector J1.
Key on.
Measure voltage between pins J1-1 (REM/FP PWR) and J1-2 (GND) at the REM harness connector.
Is voltage greater than 10.5 volts?

Yes No
KEY OFF. GO to KB49 (The FPDM functions are incorporated in the Rear Electronics Module (REM). In the following test steps, if directed to complete an action with the FPDM, complete the action with the REM. Refer to the pin numbers in the beginning of this pinpoint test). GO to KB62 .

KB62 CHECK REM/FP PWR CIRCUIT VOLTAGE TO REM USING CHASSIS GROUND AS A REFERENCE
Key on.
Measure voltage between pin J1-1 of the REM harness connector and chassis ground.
Is voltage greater than 10.5 volts?

Yes No
REPAIR open ground circuit in harness to pin J1-2 of the REM. KEY OFF. GO to KB63 .

KB63 CHECK FOR B+ TO FUEL PUMP RELAY HARNESS CONNECTOR
Disconnect fuel pump relay.
Measure B+ circuit voltage at fuel pump relay harness connector.
Is voltage greater than 10.5 volts?

Yes No
GO to KB64 . VERIFY condition of related fuse(s). If OK, REPAIR open circuit. If B+ fuse is damaged, CHECK for B+ short to ground or FP RTN for short to power before replacing fuse.

KB64 CHECK FOR IGN START/RUN VOLTAGE (THROUGH IFS SWITCH) TO FUEL PUMP RELAY HARNESS CONNECTOR
Disconnect REM connector J3.
Key on.
Measure IGN START/RUN circuit (from IFS switch) voltage at fuel pump relay harness connector.
Is voltage greater than 10.5 volts?

Yes No
KEY OFF. GO to KB65 . VERIFY condition of related fuse. If fuse is damaged, CHECK for IGN START/RUN circuit short to ground before replacing fuse. If fuse is OK, GO to KB69 (to isolate open circuit).

KB65 CHECK GROUND CIRCUIT TO FUEL PUMP RELAY
Measure resistance of ground circuit between the fuel pump relay harness connector and ground.
Is resistance less than 5.0 ohms?

Yes No
GO to KB66 . REPAIR open circuit.

KB66 CHECK REM/FP PWR CIRCUIT CONTINUITY
Measure resistance of REM/FP PWR circuit between the fuel pump relay harness connector and the REM harness connector (pin J1-1).
Is resistance less than 5.0 ohms?

Yes No
REPLACE fuel pump relay. REPAIR open circuit.

KB67 CHECK REM/FP PWR, REM GROUND AND CIRCUITS ASSOCIATED WITH THE FUEL PUMP RELAY FOR INTERMITTENTS
Disconnect REM connector J1.
Connect a non-powered test lamp between pins J1-1 (REM/FP PWR) and J1-2 (GND) of the REM harness connector.
Key on.
Observe test lamp for an indication of a fault while completing the following (the test lamp will go out when a fault is detected):
Shake, wiggle and bend the REM/FP PWR and GND (pin J1-2) circuits to REM.
Shake, wiggle and bend the circuits going to the fuel pump relay (IGN START/RUN, B+ ground).
Lightly tap the fuel pump relay and IFS switch to simulate road shock.
Is a fault detected?

Yes No
ISOLATE fault and REPAIR as necessary. KEY OFF. GO to KB68 .

KB68 CHECK FP PWR AND FP RTN CIRCUITS FOR INTERMITTENT CONCERNS
Connect a DVOM (set to measure resistance) between pins J1-11 (FP PWR) and J1-12 (FP RTN).
Observe DVOM for an indication of a fault while completing the following (resistance will change suddenly [from less than 10 ohms] when a fault is detected):
Shake, wiggle and bend the FP PWR and FP RTN circuits between the fuel pump and REM.
Connect DVOM between pin J1-12 (FP RTN) and ground.
Observe DVOM for an indication of a fault while completing the following (resistance will change suddenly [from greater than 10,000 ohms] when a short to ground is detected):
Shake, wiggle and bend the FP PWR and FP RTN circuits between the fuel pump and REM.
Is a fault indicated?

Yes No
ISOLATE fault and REPAIR as necessary. KEY OFF. Unable to duplicate or identify fault at this time. REMOVE DVOM, RECONNECT REM. GO to Z1 .

KB69 ISOLATE OPEN IN IGN START/RUN CIRCUIT
Disconnect Inertia Fuel Shutoff (IFS) switch.
Measure resistance across the normally closed contacts of the IFS switch. Note resistance.
Measure resistance of IGN START/RUN circuit between the IFS switch and fuel pump relay harness connectors.
Are both resistances less than 5.0 ohms?

Yes No
REPAIR open IGN START/RUN circuit to IFS switch. If open was in IGN START/RUN circuit, REPAIR open. If open was in IFS switch, REPLACE switch.

KB70 SENT HERE FROM PINPOINT TEST HC WITH LOW VOLTAGE AT FUEL PUMP AND NO DTCs: CHECK BATTERY VOLTAGE WITH OUTPUTS COMMANDED ON
Note: For LS6/LS8 and Thunderbird, verify REM Self-Test has been previously performed.

Scan tool connected.
Fuel pump disconnected.
Key on.
Connect digital multimeter to the battery positive and battery negative posts.
While monitoring battery voltage, command outputs on. Note voltage within 5 seconds.
Command outputs off.
Was battery voltage greater than 11.0 volts?

Yes No
GO to KB71 . Battery voltage is low. REFER to Charging System, General Information Section 414-00 in the Workshop Manual.

KB71 CHECK GROUND CIRCUIT TO FUEL PUMP BY MEASURING VOLTAGE AT FUEL PUMP USING BATTERY NEGATIVE AS A REFERENCE
Connect digital multimeter between the FP PWR circuit at the fuel pump harness connector and the battery negative post.
Key on.
While monitoring voltage, command outputs on. Note voltage within 5 seconds.
Is voltage greater than 10.5 volts?

Yes No
Ground fault to fuel pump indicated. CHECK all associated wiring and connections for the fuel pump and FPDM ground circuits. Carefully CHECK the FPDM ground connection to chassis ground. REPAIR as necessary. KEY OFF. Ground circuit to fuel pump is OK. GO to KB72 .

KB72 CHECK VOLTAGE TO FUEL PUMP DRIVER MODULE (FPDM)
Note: For LS6/LS8 and Thunderbird, the FPDM functions are incorporated in the Rear Electronics Module (REM). In the following steps, if directed to complete an action with the FPDM, complete the action with the REM.

Disconnect fuel pump driver module (FPDM).
Key on.
Measure voltage between the FPDM PWR circuit at the FPDM harness connector and the battery negative post.
Is voltage greater than 10.5 volts?

Yes No
KEY OFF. GO to KB73 . KEY OFF. Improper voltage is being supplied to FPDM. GO to KB75 .

KB73 CHECK FP PWR CIRCUIT
Connect a jumper wire between the FPDM PWR pin and FP PWR pin at the FPDM harness connector.
Key on.
Measure voltage between the FP PWR circuit at the fuel pump harness connector and the battery negative post.
Is voltage greater than 10.5 volts, AND within 0.5 volt of the reading in KB72?




Yes No
KEY OFF. REMOVE jumper. VERIFY previous test steps. CHECK related connectors for corrosion, etc. If all checks are OK, REPLACE FPDM. KEY OFF. REMOVE jumper. CHECK for causes of high resistance in FP PWR circuit.

KB75 CHECK B+ TO FPDM POWER SUPPLY RELAY (or CCRM)
Disconnect CCRM (Escort, Mustang) or FPDM power supply relay (all others).
Key on (to put same load on battery as previous steps).
For Escort, Mustang:
Measure voltage between pin 11 (B+) of the CCRM harness connector and the battery negative post.
For all others:
Measure voltage between the B+ circuit at the FPDM power supply relay harness connector and the battery negative post.
Is voltage greater than 10.5 volts?

Yes No
KEY OFF. GO to KB76 . Improper voltage is being supplied to the CCRM or FPDM power supply relay. CHECK associated wiring, connectors, etc. REPAIR as necessary.

KB76 CHECK FPDM PWR CIRCUIT
For Escort, Mustang:
Connect a jumper wire between pin 11 (B+) and pin 5 at the CCRM harness connector.
For all others:
Connect a jumper wire between the B+ and the FPDM PWR circuit at the FPDM power supply relay harness connector.
Key on.
Measure voltage between the FPDM PWR circuit at the FPDM harness connector and the battery negative post.
Is voltage greater than 10.5 volts?

Yes No
VERIFY previous test steps. CHECK related connectors for corrosion, etc. If all checks are OK, REPLACE FPDM. CHECK for causes of high resistance in associated connectors and wiring of the FPDM PWR VPWR circuit, including the IFS switch and its connector. REPAIR as necessary.

KB80 CHECK FP RTN CIRCUIT FOR SHORT TO GROUND
Disconnect REM connector J1.
Key on.
Measure voltage between pins J1-1 and J1-12 at the REM harness connector.
Is voltage less than 1.0 volt?

Yes No
GO to KB67 . REPAIR FP RTN circuit short to ground.

KB85 COMPLETE REAR ELECTRONICS MODULE SELF-TEST TO VERIFY IFS SWITCH INPUT TO REM (REM PIN J3-8)
Complete Rear Electronics Module Self-Test (refer to Workshop Manual section 419-10, Multifunction Electronic Control Modules, for directions).
Is REM DTC B2172 present?

Yes No
GO to KB86 . GO to A1 .

KB86 B2172: CHECK IFS SWITCH INPUT CIRCUIT TO REM (REM PIN J3-8)
Disconnect REM connector J3.
Key on, engine off.
Measure voltage at pin J3-8 of the REM harness connector.
Is voltage greater than 10.5 volts?

Yes No
KEY OFF.

If engine is a no start and REM DTC B2172 was received in on-demand self-test mode:

REPLACE REM.

If engine will start or REM DTC B2172 is a continuous memory DTC:

DTC is intermittent. If engine is a no start, return to Section 3 to continue diagnosis. If engine will start, GO to Z1 (even though PPT Z is designed for PCM intermittents, the diagnostic techniques will help with the REM diagnosis). KEY OFF. VERIFY IFS switch is not open. If OK, REPAIR open circuit between IFS switch and REM pin J3-8.


Read more: I had a problem with my headlight switch wiring on a 04 mustang - JustAnswer ....
Similar Threads
anyone wanting a good shortblock,heres a smoking deal
Having fuel pump issues
Fuel Pump Issues
Fuel Gauge Issues
Fuel pump issues w/ 05 explorer
Copyright © 2006-2019, Ford Mustang Forums. Privacy Policy