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
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 FP M PID may display the 75% signal as a random value that is fluctuating between 250 and 400%.
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 FP M PID may display 50%, or a random value that is fluctuating between 85 and 115%.
Observe the FP M PID for an indication of a fault while completing the following (the FP M 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.
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
ISOLATE fault and REPAIR as necessary.
No
KEY OFF. Unable to duplicate or identify fault at this time.
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
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).
No
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
REPAIR open ground circuit in harness to pin J1-2 of the REM.
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
ISOLATE fault and REPAIR as necessary.
No
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
ISOLATE fault and REPAIR as necessary.
No
KEY OFF. Unable to duplicate or identify fault at this time.
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
GO to KB71
.
No
Battery voltage is low. REFER to Charging System.
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
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.
No
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, 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 (VPWR for Continental) circuit at the FPDM harness connector and the battery negative post.
Is voltage greater than 10.5 volts? Yes
KEY OFF. GO to KB73
.
No
KEY OFF. Improper voltage is being supplied to FPDM. GO to KB75
