Code P0191

Tiny
JB_DOUCET@YAHOO.COM
  • MEMBER
  • 2004 FORD F-150
  • 4.6L
  • V8
  • 4WD
  • AUTOMATIC
  • 350,000 MILES
I keep getting P0191 code, no engine light, but my truck keeps stalling from time to time, I have replaced fuel pressure sensor, checked wiring and getting proper voltages also replace fuel filter twice and also replace fuel driver Module twice, garage says I am getting 60 psi on fuel pump. So I am at my wits end on what the problem is. Any help would be great. Thanks, Brian
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Saturday, March 7th, 2020 AT 8:15 AM

13 Replies

Tiny
ASEMASTER6371
  • EXPERT
Good afternoon,

You may have 2 issues. The stalling could be the throttle body which contains the idle air control.

https://www.2carpros.com/articles/stall-at-idle

The 191 is for the fuel pressure sensor. Were the voltages checked from the sensor to the ECM? When they checked the pressure was it running?

Roy
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Saturday, March 7th, 2020 AT 2:45 PM
Tiny
JB_DOUCET@YAHOO.COM
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Yes they were and they said fuel pressure sensor is working fine as for vacuum leaks all vacuum lines were checked as well and all okay. So I am still at a loss. :(
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Saturday, March 7th, 2020 AT 2:57 PM
Tiny
ASEMASTER6371
  • EXPERT
Then they missed something.

If it is not the pressure, and I asked about it when they checked it, and the sensor is new, it leaves wiring or ECM. The ECM is not common at all for this failure.

Roy
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Saturday, March 7th, 2020 AT 3:00 PM
Tiny
JB_DOUCET@YAHOO.COM
  • MEMBER
The mechanic the other day showed me unplugged the pressure sensor and showed my 5v from center to left side of plug then 0v from center to right side while the truck was running he poured water all over the engine compartment to see for vacuum leaks he said he could not find any he also pour water all over electrical connections while truck was running to see if it would stall and it wouldn't, every time I bring the truck to him it won't stall only seems to do it when I am alone and no one is around, sometimes I swear there is a ghost in the truck, lol.
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Saturday, March 7th, 2020 AT 3:11 PM
Tiny
ASEMASTER6371
  • EXPERT
Water? Really? Not a good idea at all.

There should be a 5-volt reference voltage and a 5-volt signal. You only have 1 of 2.

Roy
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Saturday, March 7th, 2020 AT 3:22 PM
Tiny
JB_DOUCET@YAHOO.COM
  • MEMBER
Okay, where should the other be? I am just relying on the mechanics. I am lost the only good thing is there not charging me because they are puzzled.
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Saturday, March 7th, 2020 AT 3:55 PM
Tiny
ASEMASTER6371
  • EXPERT
I attached the connector diagram.

The signal and reference need the 5 volts.

Roy
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Saturday, March 7th, 2020 AT 3:58 PM
Tiny
JB_DOUCET@YAHOO.COM
  • MEMBER
Okay, I have a volt meter. I will test it in the morning. It's dark out here now and I have no lights where the truck is. I will test it first thing in the morning myself then repost the results, thanks you in advance.

Brian
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Saturday, March 7th, 2020 AT 4:05 PM
Tiny
ASEMASTER6371
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You are welcome.

Roy
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Saturday, March 7th, 2020 AT 4:09 PM
Tiny
JB_DOUCET@YAHOO.COM
  • MEMBER
Good morning. I did the voltage checks and I am getting 5V Ref and 5V signal.
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Sunday, March 8th, 2020 AT 9:07 AM
Tiny
ASEMASTER6371
  • EXPERT
Okay, then it points right at the sensor. You may either have a bad sensor or a bad ECM.

Roy
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Sunday, March 8th, 2020 AT 2:41 PM
Tiny
JB_DOUCET@YAHOO.COM
  • MEMBER
Okay, today after I placed the message I removed the neg battery terminal and reset, now I have no codes I took the truck for a good long drive and it's not stalling. To let ya know I replaced the fuel pressure sensor 3 weeks ago.
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Sunday, March 8th, 2020 AT 5:05 PM
Tiny
ASEMASTER6371
  • EXPERT
Clearing the code makes the ECM forget the code. It fixes nothing.

Chances are it will return and the code will return.

Roy
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Sunday, March 8th, 2020 AT 5:53 PM

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