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Code 0191

spake777spake777 Member Posts: 1
edited February 22 in Mercury
I am picking up code 0191 on my scanner.
I have replaced the fuel rail pressure sensor and still have the same problem.
The car runs good until it gets to running temp then it starts missing, running rough and will eventually die.
I know that the fuel pump is running and getting fuel to the rail. Could it be the fuel pump drive module? TIA

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    thecardoc3thecardoc3 Member Posts: 5,747
    edited February 22
    The code means that the engine control module is seeing less than .2v from the fuel rail pressure sensor at pin 63. You need to use both scan data to see what the computer is seeing from the sensor, and then back that up with direct measurements of the sensor's five volt reference to make sure it is getting powered up and the signal output while the problem is occurring. It's quite likely that you are losing fuel pressure when the problem occurs. While the module "could" do that, I would expect you to have another trouble code in addition to the P0191.
    Attached is a simplified schematic of the circuit.
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