The voltage is steadily supplied to the pump and the module is pulsing the ground to turn the pump on. This shot shows the pump to driver module’s relationship clearly. Let’s zoom in on the bottom a minute (see Screen 2). This is a perfectly normal operating system, except that the time bases have been changed in the capture for display reasons. In Screen 1 you can see the diagnostic monitor (feedback) from the FPDM (blue), command from the PCM (red), voltage supply to the fuel pump (green) measured on the ground side of the pump, and the amperage/current ramp of the fuel pump (brown). Here we can see that there is about a quarter of a second time span from the time the key is switched on, until the fuel pump starts to affect the fuel rail.Ī four channel scope can be used to view nearly the entire pump control system at one time. At point 1, there is nothing happening, this was key off. What useful info can be gathered here? Let’s look at it a minute. The key was switched on, but the engine was not started. The fuel line was completely bled down to zero psi. This is the voltage signal from the FRP sensor on a 2005 Expedition. If the fuel pump fuse blew, or the inertia switch tripped, the FPDM will not power up and the PCM will store those codes.Īn oscilloscope tapped into the FRP signal lead can provide some fast and useful information about the fuel pump’s performance. So, if you get one of these vehicles with no fuel pressure, and you see the fault codes P1233 and/or P1234 (Fuel Pump Driver Module Disabled or Offline), don’t be so quick to assume the FPDM has failed. One thing to keep in mind is that, currently, the same battery positive feed used to supply the fuel pump is the same power feed used to operate the FPDM. Beware, some scanners may display the readings in the yellow column, so know your tool. The green column reflects the fuel pump monitor PID on a scanner. As you can see by the chart, that would send you in completely the wrong direction. For example, a 75% duty signal could be misread as 25%. Depending on your setting, your readings could get reversed. Be mindful of the trigger setting on your tool. The yellow column represents the duty cycle that you may see if you tapped into the FPDM monitor circuit to the PCM with a duty cycle meter or an oscilloscope. However, as simple as that may sound, reading them requires knowledge of your own tool. There are only three diagnostic monitor signals that the FPDM will return to the PCM. So you not only get to look at the system from the PCM’s “eyes,” you also get to see it through the FPDMs “eyes” too. The nice thing about diagnostics on this system is that you have two control modules that are both reporting diagnostic information. The fuel pump relay is now toggled by the ignition switch. One notable change however, is the PCM no longer controls the fuel pump relay. One Ford-specific component that still remains after more than two decades is the inertia fuel cut-off switch. A couple of things that become optional across other makes that Ford still includes are the fuel pump relay and the in-line fuel filter. This much should remain the same for any electronic returnless system. This system consists of a rotary vane fuel pump (same as before), fuel line (pressure only), fuel rail pressure sensor (that also contains a temperature sensor), fuel pump control module and, of course, the PCM. With an electronic returnless system, the PCM can now raise or lower fuel pressure at will. Also, making it electronically pressure controlled gives the PCM more flexibility over fuel control by adding another option if needed.
Robert Whitehurst, Service Dealer Solutions, Epicor.Alda Rodriguez, Service Dealer Solutions, Epicor.Tim Hardin, Senior Vice President & General Manager, Automotive, Epicor.
#2002 ford focus 2.0 fuel pump driver module problems how to#
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