Recently, we had a 2004 ford f150 with a 5.4-liter engine towed into the shop. Customer stated they were in the middle of a car wash and the engine stalled out and would not restart. Upon checking, the truck had spark but no fuel pressure when cranking. There was a diagnostic trouble code of P0191 and P1233. I was quickly able to confirm the engine has spark by verifying that the check engine light goes off while cranking the engine over and also by using my spark tester installed into the ignition coil. Next step was to plug into the 16 pin OBD2 diagnostic connector located under the dash. From there, I can pull codes and read live data using my scanner. But first, I will explain how the fuel pump operates.
Fuel Pump operation
On these vehicles, the fuel system is a bit different. Ford uses a pulse width modulated Fuel Pump Driver Module (FPDM or fuel pump control unit) to control the fuel pump speed. The Powertrain control module and inputs to the powertrain control module will determine how fast the fuel pump driver module will run. Some inputs that it uses are the fuel rail pressure sensor, throttle angle engine temperature etc. When starting the engine, the PCM sends a low current voltage down the FPM circuit. With the pump off, this voltage is pulled low by the path to ground through the fuel pump. The PCM is also able to verify that the FPDM circuit and the FP power circuit are complete from the FPDM splice through the pump to ground. This also confirms that the FP power or FPDM circuits are not shorted to power. With the pump running, voltage is now being supplied from the pump relay to the FP power and FPDM circuits. With the pump on and the FPDM circuit high, the PCM can verify that the FP power circuit from the fuel pump relay to the FPDM splice is complete. It can also verify that the fuel pump relay contacts are closed and there is a B+ supply to the fuel pump relay.
Current codes in the computer
The first two codes below are the two that were in the PCM when I plugged into the computer or obd2 diagnostic connector under the dash. The third code I have listed below was not stored in the computer but can very well be flagged by the PCM if the fuel pump driver module stops communicating altogether.
DTC P1233 – Fuel System Disabled Or Offline
Escort/Tracer (only): FPDM PWR circuit is open, or the CCRM pin 11 is open to battery voltage, or the CCRM is damaged
FPDM ground circuit is open, or FPM circuit is open or shorted
Inertia fuel shutoff switch needs to be reset
The diagnostic trouble code P1233 code indicates an issue with the fuel pump driver module. This code can also be set if power to the fuel pump driver module is open (faulty fuel pump relay or inertia/fuel cut-off switch is tripped). This P1233 diagnostic trouble code sets when the Powertrain ContrModule loses communication with the FPDM.
DTC P0191 – Fuel Rail Pressure Sensor Circuit Performance
The comprehensive component monitor checks the FRP for acceptable fuel pressure. The test fails when the fuel pressure falls below or exceeds a minimum/maximum calibrated value for a calibrated period of time.
High fuel pressure.
Low fuel pressure.
Damaged FRP sensor.
Excessive resistance in the circuit.
Low or no fuel.
The diagnostic trouble code P0191 indicates an issue with the fuel rail pressure transducer sensor which is located on the top left of the engine on the fuel rail. Based on my experience, this code will also set if there is no or low fuel pressure.
Sometimes the PCM will flag a code P1235 if the fuel pump control unit does not respond at all so you may see this code as well. However, this particular vehicle did not set this code.
DTC P1235 – Fuel Pump Control out of range
The diagnostic trouble code P1235 indicates the FPDM detected an invalid or missing FP circuit signal from the PCM. The FPDM sends a message to the PCM through the FPM circuit, indicating this failure was detected. The PCM sets the DTC when the message is received.
Note: Certain vehicles the FPDM functions are incorporated in the Rear Electronics Module (REM). Also, the REM does not use an FPM circuit. Diagnostic information is sent on the communication link.
FP circuit open or shorted
ETC system concern
Fuel Pump Circuit operation.
The power for the fuel pump circuit starts at the PCM power relay which is located inside the vehicle in the central junction box on the right a-pillar (right kick panel). The PCM power relay is activated when the key is turned “on”. From there, it supplies power to many components including the fuel pump relay. When this happens, the fuel pump relay energizes and sends power to the inertia switch and then allows power through (if the inertia switch is not tripped) to the fuel pump driver module. The ground for the fuel pump relay is also located in the right-hand A-pillar.
On this F-150, there are two important fuses for this circuit. They are as follows. F2.28 (5 amp fuse powers up the PCM relay) and F2.34 (20 amp fuse that powers up the fuel pump relay). Without these two fuses working or in place, the fuel pump circuit will not operate.
Note: Keep in mind, the ignition switch powers up or activates the PCM power relay. So if you’re not getting power on this circuit and or trying to diagnose a no start condition but don’t have power on multiple circuits, be sure to check the inputs to the PCM power relay and ignition switch.
Our next step was to access the fuel pump circuit to check the operation. This can be done at the FPDM or the fuel pump. Since the wiring for the fuel pump cannot be accessed without lowering the fuel tank, it was much easier to do the testing right at the fuel pump driver module which is located under the vehicle above the spare tire. Because of its location, it has a high failure rate due to road salt and water intrusion, so I decided to take a look. (While it was not enjoyable to access the module underneath the vehicle, it sure beats dropping the fuel tank to gain access to the fuel pump wires to do some testing).
Here is are some pictures of the fuel pump driver module located above the spare tire. (Before the spare tire was removed) As you can see, it is a tight fit and the spare tire needed to be removed in order to gain access to the wires and module to do some testing.
After the spare tire was removed and we were able to gain access to the fuel pump driver module we can run all of our tests. Before going further, I could see the fuel pump driver module was extremely corroded due to the bitter cold winters the truck has been through. However, because it is important to diagnose the problem accurately, it was not enough information to confirm it was bad: I needed more concrete evidence. In addition, how do we know the fuel pump itself is not at fault? Just because the module is corroded, does not mean it is bad. This is where the electrical testing came into play.
The module itself needs battery voltage and a good ground to operate. Using the right wiring diagram from alldata, I was able to determine the white wire is the power supply from the inertia switch and fuel pump relay. The black wire with yellow stripe wire is the ground. The pink wire with black stripe and a brown wire with white stripe goes directly to the fuel pump inside the fuel tank. The other two wires (light blue/orange and white/yellow wire) go to the fuel pump driver module and PCM. This is the signal and monitor wire so the PCM can control the fuel pump driver module and know what the results are. With an assistant in the driver’s seat cranking the engine over, I was able to confirm power and ground at the module real quick so I knew there was not a power supply problem going to the fuel pump driver module.
Reading Fuel Pump Driver Module signals using a scan tool.
One of the easiest ways to diagnose this no start issue is by using a scan tool that can read live data from “data stream”. Some scan tools will give you the fuel pressure based on the fuel rail pressure sensor signal or voltage, some will provide you with the duty cycle for the FPDM and some will provide both readings. I have put together a list of both below.
4.5 volts = 70 psi
3.9 volts = 60 psi
3.4 volts = 50 psi
2.8 volts = 40 psi
2.2 volts = 30 psi
1.6 volts = 20 psi
1.1 volts = 10 psi
0.5 volts = 0 psi
Keep in mind, that the FRPS reading on the scan tool will read 8 to 10 psi higher than compared to when a mechanical fuel pressure gauge is connected to the fuel rail unless the vacuum hose is removed from the FRPS. Then the readings will come close to matching each other. This is normal operation.
Below is a list of duty cycles from the PCM to the FPDM as commands to run the fuel pump and signals from the FPDM back to the PCM to indicate whether or not the FPDM is functioning properly and received the signal from the PCM.
FPDM commands back to PCM
50% Duty cycle indicates the FPDM is functioning properly.
25% Duty cycle indicates the FPDM either did not receive a Fuel Pump duty cycle command from the PCM or did not receive a valid FP cycle command from the PCM.
75% Duty Cycle indicates that the FPDM detects a concern in the circuit between the fuel pump and FPDM
Fuel Pump signal commands sent from the PCM to the FPDM.
0 to 4% The PCM will not output this duty cycle. This is an invalid duty cycle. If the FPDM sees this request, it will send back the 25% duty cycle signal to the PCM.
4 to 5% Not a valid signal. The FPDM will do nothing.
5 to 45% This is a normal operating range. The fpdm will operate the fuel pump at the speed requested. When the FPDM sees this signal, it will run the fuel pump twice the speed of the signal. For example, 30% duty cycle from the computer the FPDM will run the fuel pump at 60%. The FPDM will send a duty cycle signal back to the PCM of 50% indicating everything is functioning properly
45 to 48% Normal operation. An open circuit cannot be detected in this range. The FPDM will operate the fuel pump at the requested speed. Again, twice double the signal sent from the PCM.
48 to 51% Normal operation. The FPDM will operate the fuel pump at 100%. FPDM will send a 50% duty cycle signal back to the PCM on the FPM circuit indicating everything is functioning properly.
51 to 52% is not a valid signal. No action will be taken by the FPDM
52 to 68% The PCM will not send this signal to the FPDM. It is an invalid signal. If the FPDM sees this signal, it will send the 25% duty signal back to the PCM on the FPM circuit indicating the FPDM either did not receive a fuel.
68 70% is not a valid signal. No action wil be taken by the FPDM.
70 to 81% the PCM will send this signal to the FPDM when it requests the fuel pump off. The FPDM will not operate the fuel pump and FPDM will send a 50% duty cycle signal back to the PCM on the FPM circuit indicating is functioning properly.
81 to 83% is not a valid signal. The FPDM will do nothing.
83 to 100% the PCM will not output this signal to the FPDM. If the FPDM sees this signal, the FPDM will send the 25% Duty cycle back to the PCM indicating an invalid signal or command from the PCM.
Below is a video of a different Ford F-150 that does not start due to a failed fuel pump driver module. You will notice the truck in the video has the same codes in the computer as the one above. The diagnostic trouble codes are P0191 and P1233.
Unfortunately, the customer was a victim of a poor design flaw by Ford. Doing the regular maintenance for the vehicle still, would not have prevented this corroded fuel pump driver module. The only thing that the customer could have done is get it inspected or simply replaced before the component stalled out if they were aware of this issue. After installing the new fuel pump driver module, the truck started and ran great! We were able to clear the diagnostic trouble codes P0191 and P1233 using our scanner and they did not come back. The customer was pleased to have their vehicle back up and running.
Below is a list I have put together of Ford, Lincoln, Mercury and Mazda vehicles that use Fuel Pump Driver Modules from 2004 to 2011. Please note, this is not a complete list.
2004 Ford F150 and F150 Club Wagon, E250, E350 Super Duty 5.4L and 6.8L, E350 Club Wagon 5.4L, E450 Super Duty 6.8L
2005 Ford E150, E150 Club Wagon, Ford E250, E350 Club Wagon 6.8 E350 Club Wagon 5.4, E350 Super Duty 6.8, F-350 Super Duty 5.4L, F-450 Super Duty 6.8L, F-550 Super Duty 6.8L, Ford GT, Mustang, Lincoln Navigator, Mazda Tribute 2.3L, Mazda Tribute 3.0L, Mercury Mariner 2.3L, Mercury Mariner 3.0L
2006 Lincoln Town Car, Mazda Tribute 2.3L, Mazda Tribute 3.0L, Mercury Grand Marquis, Mercury Mariner, Ford Crown Victoria, Ford E150, Ford E250, E350 Super Duty 6.8L, E350 Super Duty 5.4L, E450 Super Duty 6.8L, Escape 2.3L, Ford Escape 3.0L, Expedition 5.4L, F150, F250 Super Duty 6.8L, F250 Super Duty 5.4L, F350 Super Duty 6.8L, Ford F350 Super Duty 5.4L, F450 Super Duty 6.8L, F550 Super Duty 6.8L, Ford GT, Mustang, Lincoln Mark LT 5.4L, Lincoln Navigator 5.4L
2007 Ford Crown Victoria, E-150, E-250, E-350 Super Duty 6.8L, E-350 Super Duty 5.4L, E-450 Super Duty 6.8L, Escape, Expedition 5.4L, Ford Explorer Sport Trac, F-150, F-250 Super Duty 6.8L, Ford F-250 Super Duty 5.4L, F-350 Super Duty 6.8L, F-350 Super Duty 5.4L, Ford F-450 Super Duty 6.8L, F-550 Super Duty 6.8L, Mustang 4.0L, Mustang 4.6L, Lincoln Mark LT 5.4L, Lincoln Navigator 5.4L, Lincoln Town Car, Mercury Grand Marquis, Mercury Mariner
2008 Ford Crown Victoria, E-150, Ford E-250, E-350 Super Duty 6.8L, E-350 Super Duty 5.4L, E-450 Super Duty 6.8L, Escape 2.3L, Ford Escape 3.0L, Ford Expedition, Explorer Sport Trac, F-150, 250 Super Duty 6.8L, F-250 Super Duty 5.4L, F-350 Super Duty 6.8L, F-350 Super Duty 5.4L, F-450 Super Duty 6.8L, F-550 Super Duty 6.8L, Mustang 4.0L, Ford Mustang 4.6L, Lincoln Mark LT 5.4L, Lincoln Navigator 5.4L, Lincoln Town Car, Mazda Tribute 2.3L, Mazda Tribute 3.0L, Mercury Grand Marquis, Mercury Mariner
2009 Ford Crown Victoria, Explorer Sport Trac, F-250 Super Duty 6.8L, F-250 Super Duty 5.4L, F-350 Super Duty 6.8L, F-350 Super Duty 5.4L, F-550 Super Duty 6.8L, Mustang 4.0L, Mustang 4.6L, Lincoln Town Car, Mazda Tribute V6 181 3.0L, Mercury Grand Marquis
2010 Ford Crown Victoria, Explorer Sport Trac, F-250 Super Duty 6.8L, F-250 Super Duty 5.4L, F-350 Super Duty 6.8L, Ford F-350 Super Duty 5.4L, F-550 Super Duty 6.8L, Mustang 4.0L, Mustang 4.6L, Lincoln Town Car, Mazda Tribute 3.0L, Mercury Grand Marquis
2011 Ford Crown Victoria, Lincoln Town Car, Mazda Tribute 3.0L, Mercury Grand Marquis
2004 Ford F150 5.4 stalled out no start due to corroded fuel pump driver module.