P1235 - Fuel Pump Control Out Of Range
Note: For LS6/LS8 and Thunderbird, the FPDM functions are incorporated in the Rear Electronics Module (REM). Also, the REM does not use a FPM circuit. Diagnostic information will be sent through SCP.
P1235 indicates that the FPDM has detected an invalid or missing FP circuit signal from the PCM. The FPDM will send a message to the PCM through the FPM circuit, indicating that this failure has been detected. The PCM will set the DTC when the message is received.
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
Is voltage greater than 10.5 volts?
Yes
No
Key off. REPLACE FPDM.
GO to KB4 .
KB4 CHECK POWER TO FPDM
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)
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
Is resistance less than 5.0 ohms?
Yes
No
GO to KB7 .
SERVICE open ground circuit.
KB7 CHECK FOR OPEN FPDM PWR CIRCUIT
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
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
Is resistance less than 5.0 ohms?
Yes
No
GO to KB10 .
REPAIR open circuit.
KB10 CHECK FOR OPEN FPDM PWR CIRCUIT
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
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
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.
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
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
Is resistance greater than 10,000 ohms?
Yes
No
GO to KB18 .
REPAIR short circuit.
KB18 CHECK FOR FPM OUTPUT FROM FPDM
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.
Your best bet , take it to a qualified repair shop.
C1123
Vehicle Speed Circuit Fault
Overhead Console Module
REFER to Section 413-08 .
SOURCE: when my car warms up it wont go any faster then 25 to 30 mph
if your car will only travel at 25 to 30 mph the catalytic converter is plugged up will need to change to correct problem.
SOURCE: Have 1989 Lincoln Town Car. Transmisson will not
Are you sure the trans is in 3rd. Pull the stick into low gear accelerate shift to 2nd about 20 mph shift to 3rd about 35 mph then 4th about 50 mph. This will let me know how to go further with your problem. If you do this proceedure write the results on this Great FixYa Page!
Check the tires air pressure. It happened to me 01lincoln town car, .had 60 psi in the front and 35 psi in the rear. This effectively gives you twould different tire sizes front and rear, the problem is that the speed sensors are reading two different mph from front and rear tires and causes the computer to go into limp mode. The Solution is to check the air pressure in the tires and make sure that all 4 tires have the same psi. Sometimes it's just that simple
Common Problems That Trigger the P0731 Code
If you aren't comfortable diagnosing these points, take it to a reputable shop.
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