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Old 01-07-2012, 10:08 AM
Junior Member
Join Date: Mar 2011
Location: Muskoka
Posts: 26
Default PO193 Fault code

I keep getting this fault code. Is there a way to troubleshoot which component to replace?
The van is running fine, what could potentially go wrong if I keep driving it?

61 Falcon 351C 4 speed 8.8
99 Mustang GT
03 HD Sportster
2000 F150 4x4
2004 Freestar (the wifes!)
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Old 01-07-2012, 10:14 AM
Senior Member
Join Date: Jan 2006
Posts: 1,234

Look at the fuel rail pressure sensor. That code is for too high voltage. The following will describe the code and what can possibly be the problem. It was eaier to copy and paste instead of typing a lot.

P0193 Description

The Fuel Rail Pressure (FRP) sensor is a diaphragm strain gauge device in which resistance changes with pressure. The electrical resistance of a strain gauge increases as pressure increases, and the resistance decreases as the pressure decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signal to the Powertrain Control Module (PCM) corresponding to pressure.

Strain gauge type sensors are consider passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow.

Voltage that is dropped across a fixed resistor in series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.

The FRP sensor measures the pressure of the fuel near the fuel injectors. This signal is used by the PCM to adjust the fuel injector pulse width and meter fuel to each combustion cylinder.


- Engine Light ON (or Service Engine Soon Warning Light)
- Engine will not start

Possible Causes

- Excessive resistance in the circuit
- Low or no fuel
- Wiring harness connector of the fuel pressure sensor
- Fuel Rail Pressure Sensor
- Fuel Pump
People are like Slinkies. Not much use, but it still makes me smile whenever I see one tumble down the stairs.
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Old 01-07-2012, 11:14 AM
Senior Member
Join Date: May 2011
Location: Colorado, near Denver
Posts: 670

Ok, what really happened here is that the FRP went over 4.5V for over 2 seconds, when the fuel pump pressure (as read by the sensor) should have been much lower, was commanded lower, and did not respond.
This code is usually caused by a short to vref. The easiest way to troubleshoot is to disconnect it and see if a P0190 sets. If it does, this is probably an internally shorted sensor. If not, there is most likely a wiring problem, possibly in the pcm. Note: this code is almost NEVER caused by a pcm problem.
Another way to troubleshoot is to look at the FRP when the engine is running; it should have a fuel pressure of somewhere around 35-80 psi when running (I would assume this is the Freestar?). That's about what all these electronic returnless systems ran at. The pressure will most likely be around 40 psi if all is well.
If this sensor is removed from the rail, it is common to see a fuel leak from them when reinstalled. Not always a problem, but BE CAREFUL with fuel.
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