Fuel problem, code P0190

dtorres3

New Member
Sep 13, 2006
7
0
1
San Antonio
#21
I saw this post about the P0190 code. I have been having issues with the code popping up every once in a while. Back story, I replaced the fuel pump, with a Bosch because it would not start or hold fuel pressure at the fuel rail. It started fine and ran great. however, now I am getting that error code. I replaced the FRPS and EGR valve on two separate occasions. Still doing it. I checked for a leaky injector, but couldn't fine one. I did check my ref. voltage, which was at 5V. My scanner read 15 psi for fuel pressure, which I thought was probably wrong. But reading all these posts, I think my new fuel pump may still be the issue. My other thought was, it may be my vacuum lines or injectors. Other than that, the car runs great and has 191565 miles on it. Pulling my hair out, Advice? I have a video I took today with the fuel pressure at idle at 28 psi. When I turn off the car, it drops almost back to zero in about 30 seconds. But I cannot attach it. When I turn ignition on it goes up to like 20 psi. The freeze frame may be wrong, but why the pressure drop?
 

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Onesick99GT

Active Member
Nov 20, 2018
212
25
38
32
Dayton, Ohio
#22
15 psi is way too low for fuel pressure. Refer to your manual on what your psi should be. I believe it should be around 40 for 99-04 mustangs.
 
Sep 8, 2018
55
3
18
63
Jacksonville, Florida
#23
I never had the code come up again after I replaced my fuel pump. Like the post above says, fuel pressure should be 40 psi. I am no mechanic but I too would suspect the fuel pump. Would not be the first new pump to go bad. Just wondering, did you use a new screen filter on the fuel pump when you replaced it? Also did you replace the inline filter? On my crown vic it got to where it would not run. I changed the fuel filter and the old one was full of what looked like mud. A new filter did the trick on it.
 

dtorres3

New Member
Sep 13, 2006
7
0
1
San Antonio
#24
Black GT, yeah the new pump had a new screen filter with it, the inline filter was the second thing I replaced. I read the scanner manual, maybe I did not clear the FF screen, but that did sow up after the p0190 code. Onesick99GT, I agree. However, the car runs prefectly fine other that the codes. i had over 250 miles on one full tank, with more to go. so, my gas mileage is not effected. I guess I will have to get another pump. Thanks for your input.
 

Onesick99GT

Active Member
Nov 20, 2018
212
25
38
32
Dayton, Ohio
#26
Did you check for a fuel leak anywhere underneath the car after replacing the fuel pump.
 

wmburns

SN Certified Technician
Aug 14, 2009
5,069
373
164
Houston Texas
#28
IMO the odds favor a problem with the fuel rail pressure sensor (FRPS) and not the fuel pump. Why? Look carefully at the details DTC code.

Anytime the DTC code calls out a "circuit Malfunction" it means that something is sooooooo wrong with the circuit that the PCM isn't able to perform any meaningful trouble shooting. Think,
  • Bad FRPS. Think ruptured disk. Note, if the fuel pump is massively over sized this could play a role in the failure.
  • Bent or pushed pins
  • corrosion
  • Wiring harness fault
  • Ground short or short to another wire.
OBTW, regarding possible fuel leaks. Don't overlook places for leak where the fuel will NOT be seen. Examples include:
  • Fuel pump check valve
  • Flexible fuel line in the gas tank. The leak stays inside the tank.
  • FRPS, Likely a leak will be drawn into the intake vacuum reference vacuum line.
  • Fuel injectors themselves. Note the leak could only be a few drops that will go directly inside the intake valve and will never been seen.
All parts of the fuel system should hold pressure between starts.

>>>
P0190 - Fuel Rail Pressure Sensor Circuit Malfunction (FRP)

The comprehensive component monitor (CCM) monitors the FRP sensor to the PCM for VREF voltage. The test fails when the VREF voltage from the PCM drops to a voltage less than a minimum calibrated value
  • VREF open in harness.
  • VREF open in sensor.
  • VREF open in PCM
Verify VREF voltage between 4.0 and 6.0V.
 
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Sep 13, 2006
7
0
1
San Antonio
#29
wmburns, I appreciate your thorough analysis. The car threw the code again, p0190. I checked the VREF again, and it is 5VDC. I checked my FF on my scanner again, the fuel pressure went from 13.9 last time to 11.3 psi, this time. plus the idle sounds rough now. I already replaced the EGR and FRPS when my issues continued after I replaced my my fuel pump, when car initially wouldn't start two months ago. I guess the cheaper route would be to replace the FRPS again. I will keep you posted.
 

wmburns

SN Certified Technician
Aug 14, 2009
5,069
373
164
Houston Texas
#30
I guess the cheaper route would be to replace the FRPS again.
IMO the cheaper route is perform some additional measurements.

When monitoring the ODB2 fuel pressure PID at idle, remove the intake vacuum reference line. What does the fuel pressure do? Hint. at idle it should go up (or at least change). On a normal car it should go from 32 PSI to 40 PSI as measured with an external gauge.

TEST: Force a specific signal return. Disconnect the FRPS and short the signal return to VREF. What does the fuel pressure PID do? Now short the signal return to the VREF Ground. What does the PID do?

Hint. this test should force the FRPS to go to either a max or min value. What we are trying to do is to CONFIRM that the PCM is actually "seeing" the signal return.

Cost: zero.

Try to resist the urge to be a "parts changer" unless there is no other option. This goes double when replacing the same part more than once.
 
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Sep 13, 2006
7
0
1
San Antonio
#31
wmburns, here are my results. My fuel pressure at idle is 28-29. When I removed the vacuum line, it jumped to 39psi. Resistance between 1-3 was 4..69K. If I did the test for the signal return correctly, the pressure jumped past 70psi and the engine shut off. I was not sure, but it was pins 2-3. I did it twice, twice the car shut off. The weird part is, (not sure if something got unstuck), but I thought I was done, so I was going to remove my temp fuel pressure gauge and noticed that my fuel pressure didn't drop! I tried turning the car on and off again,but to my surprise the pressure remained. I pulled the fuse out to release the fuel pressure. started it again and it started right up. The good news, is I hope it is fixed, but I think something will fail soon. wmburns THANKS for your troubleshooting tips! I wass going nuts.
 

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