Capless fuel filler and check engine light
08-26-2018, 03:55 PM
#101
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I have spent some time researching this issue and have come up with some new details. The PCM runs a specific test to determine if the P0451 offset condition exists. This test is only one component of the overall evap test.
This test runs when the truck is initially started. The computer is looking to see if there is a condition where excessive pressure or vacuum exists in the fuel tank. This specific test executes every start cycle regardless of outside temperature or fuel level. The only requirement for the computer to execute this specific test is that the car must have sat previously for 2 hours. Here is the Ford document that explains details for obd tests for the 2010 MY.
Specifically, P0451 will set if the computer sees the FTP pressure to be more than 2.0 in H20, OR, less than -2.0 in H20 during engine start.
With this background knowledge, I looked at Ford’s HX39 procedure again (the instructions Ford provides to troubleshoot this issue). There are essentially 2 reasons this excessive pressure/vacuum condition would exist.
Last night, the conditions outside were ripe to set the code in my truck (cold + rain). I went out this morning and hooked up my analyzer before starting the vehicle. The FTP sensor read 14.45 in H20. At this value, the computer should set P0451. To rule out #1 above, I put in the supplemental refueling adapter and continued to monitor the FTP pid. No change. There is not excessive pressure in my tank. I started the vehicle, and sure enough, P0451 set. Because of this excessive pressure condition, I can rule out the #1 and capless fuel filler being the culprit for my issue that others have mentioned.
During the drive in to work, the FTP pid remained around the same value. After sitting all day in the dry sun, the FTP pid read around 1.5 in H20 on the way home.
I remember noticing that the actual FTP sensor sits between the truck cab and the truck bed. From up-top, if you shine a flashlight in the gap, you will actually see the top of the FTP sensor and wiring. Essentially, the FTP sensor is exposed to the elements. I decided to drop a bucket of water on this area and monitored the FTP pid. Sure enough, the pressure started to rise to an unacceptable level.
I do not know for sure if the sensor or wiring is at fault. I am leaning towards senor as the PCM analyzes the voltage coming back from the sensor and as voltage increases, so does pressure.
Too bad the FTP sensor is only sold as an assembly with associated fuel lines at a cost of $300+ from the dealer.
I may try shielding the actual sensor from water by enclosing it in a plastic bag with zip ties, knowing there will be small holes for the wiring and fuel lines.
This test runs when the truck is initially started. The computer is looking to see if there is a condition where excessive pressure or vacuum exists in the fuel tank. This specific test executes every start cycle regardless of outside temperature or fuel level. The only requirement for the computer to execute this specific test is that the car must have sat previously for 2 hours. Here is the Ford document that explains details for obd tests for the 2010 MY.
Specifically, P0451 will set if the computer sees the FTP pressure to be more than 2.0 in H20, OR, less than -2.0 in H20 during engine start.
With this background knowledge, I looked at Ford’s HX39 procedure again (the instructions Ford provides to troubleshoot this issue). There are essentially 2 reasons this excessive pressure/vacuum condition would exist.
- There is a problem with the EVAP system / purge solenoid / charcoal canister where there really is excessive pressure or vacuum in the fuel tank.
- The FTP sensor is giving false readings.
Last night, the conditions outside were ripe to set the code in my truck (cold + rain). I went out this morning and hooked up my analyzer before starting the vehicle. The FTP sensor read 14.45 in H20. At this value, the computer should set P0451. To rule out #1 above, I put in the supplemental refueling adapter and continued to monitor the FTP pid. No change. There is not excessive pressure in my tank. I started the vehicle, and sure enough, P0451 set. Because of this excessive pressure condition, I can rule out the #1 and capless fuel filler being the culprit for my issue that others have mentioned.
During the drive in to work, the FTP pid remained around the same value. After sitting all day in the dry sun, the FTP pid read around 1.5 in H20 on the way home.
I remember noticing that the actual FTP sensor sits between the truck cab and the truck bed. From up-top, if you shine a flashlight in the gap, you will actually see the top of the FTP sensor and wiring. Essentially, the FTP sensor is exposed to the elements. I decided to drop a bucket of water on this area and monitored the FTP pid. Sure enough, the pressure started to rise to an unacceptable level.
I do not know for sure if the sensor or wiring is at fault. I am leaning towards senor as the PCM analyzes the voltage coming back from the sensor and as voltage increases, so does pressure.
Too bad the FTP sensor is only sold as an assembly with associated fuel lines at a cost of $300+ from the dealer.
I may try shielding the actual sensor from water by enclosing it in a plastic bag with zip ties, knowing there will be small holes for the wiring and fuel lines.
I also have had a pending p1450 but not sure if that was related?
How did you make out with it?
thanks
08-26-2018, 10:50 PM
#102
Senior Member
I've been living with the issue. The dealer had 3 failed opportunities to fix it. I feel like I can drop a bucket of water between the cab and box (which is right where the ftp sensor is mounted) and will blow p0451. I've tried dielectric grease in the connector. Also tried wiggling on the harness, connector and ftp sensor while a scan tool was hooked up without seeing any fluctuations. My ftp sensor has been replaced.
Also of interest, the code blows right in the split second when the engine cranks. I hooked up a scan tool before starting, no code. Crank, code p0451. When I graph the FTP PID, I see an extreme spike for that split second. In the freeze frame data for the event, the runtime indicator indicates that it occurred during the 0sec mark – right at startup. Noise on some nearby wiring?
I've thought of encasing the ftp sensor, connector, and surrounding wiring in self amalgamating tape. Only issue is it’s difficult to reach the area without removing something. I can feel all the components and remove the connector blind with one hand. Applying that tape is a different issue. To make the job doable, you would need to do one of the following: 1. Drop (partially) the fuel tank 2. Drop the drive shaft OR 3. Unbolt the box and slide it to the side. None of those options sounded good to me, especially that I didn't have a guarantee that the self amalgamating tape would fix the problem.
My truck will likely go to the junkyward with this issue. Its a nuisance with no drivability concerns.
Also of interest, the code blows right in the split second when the engine cranks. I hooked up a scan tool before starting, no code. Crank, code p0451. When I graph the FTP PID, I see an extreme spike for that split second. In the freeze frame data for the event, the runtime indicator indicates that it occurred during the 0sec mark – right at startup. Noise on some nearby wiring?
I've thought of encasing the ftp sensor, connector, and surrounding wiring in self amalgamating tape. Only issue is it’s difficult to reach the area without removing something. I can feel all the components and remove the connector blind with one hand. Applying that tape is a different issue. To make the job doable, you would need to do one of the following: 1. Drop (partially) the fuel tank 2. Drop the drive shaft OR 3. Unbolt the box and slide it to the side. None of those options sounded good to me, especially that I didn't have a guarantee that the self amalgamating tape would fix the problem.
My truck will likely go to the junkyward with this issue. Its a nuisance with no drivability concerns.
11-06-2018, 07:45 PM
#103
Having the same problem with my 2011 5.0. Fuel door came loose, Check engine light, Check Fuel inlet message, code Po455..Fixed the door but still getting check engine.
Someone mentioned that they put a locking cap on capless fuel inlet and it worked. Unfortunately, not for me. Bought the cap and didn't have a good feel about it. Cap is plastic with a small lever to keep it locked. Not much to it. Had cleared the code and it took a couple of days to come back on but there is the check engine light. So far, no Check fuel inlet message but suspect it will come up soon.
Due for inspection next month, If it is showing any kind of code it will not pass. Maybe looking at having the tube and door replaced. Truck just passed 100,000 mi as well. Pain in the ***.
Someone mentioned that they put a locking cap on capless fuel inlet and it worked. Unfortunately, not for me. Bought the cap and didn't have a good feel about it. Cap is plastic with a small lever to keep it locked. Not much to it. Had cleared the code and it took a couple of days to come back on but there is the check engine light. So far, no Check fuel inlet message but suspect it will come up soon.
Due for inspection next month, If it is showing any kind of code it will not pass. Maybe looking at having the tube and door replaced. Truck just passed 100,000 mi as well. Pain in the ***.
12-07-2018, 10:49 PM
#104
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Add me to the list. I just bought my 2013 and I think the guy I bought it from had re entry reset the codes because the day after I bought it, the light came on tripping both 0451 and 0455. Not knowing any better, I replaced the purge valve which did fail the finger test (pulling vacuum with the electrical connector unplugged). After replacing it my engine light went off for a week or more which seems odd because one of the codes was permanent and the reader did not pull the code anymore after changing the purge valve.
But it’s back now with the 2 permanent codes. this is more than a nuisance because I need to pass an emissions test in the coming 60 days. I’m feeling disheartened that there seems no good fix . I certainly don’t want to throw piles of money at this to pass emissions.
i have been monitoring the PID. I have 2 different apps and strangely they show the PID data differently, OBD fusion shows it as pounds per h20 and carscanner shows it as k/pa I think it is. The latter of which is very erratic but tends to stay mostly static at 7182.25 but does show erratic spikes down into negative pressure ranges and sometimes will zig zag.
the h20 chart in OBD fusion has the PID basically stuck at 14.75 or 15. I couldn’t get it to fluctuate at all neither by funnel banging nor by jiggleinh the wires had hoses above the tank.
it seemed like one time I jiggled something with the other app and was able to achieve some data that looked more normal but I was never able to duplicate that.
maybr I’ll try disconnecting the connector and doing the grease and see what that gets me.
any other newly learned things with this? Is it a wiring issue or a poorly designed sensor issue do you think?
But it’s back now with the 2 permanent codes. this is more than a nuisance because I need to pass an emissions test in the coming 60 days. I’m feeling disheartened that there seems no good fix . I certainly don’t want to throw piles of money at this to pass emissions.
i have been monitoring the PID. I have 2 different apps and strangely they show the PID data differently, OBD fusion shows it as pounds per h20 and carscanner shows it as k/pa I think it is. The latter of which is very erratic but tends to stay mostly static at 7182.25 but does show erratic spikes down into negative pressure ranges and sometimes will zig zag.
the h20 chart in OBD fusion has the PID basically stuck at 14.75 or 15. I couldn’t get it to fluctuate at all neither by funnel banging nor by jiggleinh the wires had hoses above the tank.
it seemed like one time I jiggled something with the other app and was able to achieve some data that looked more normal but I was never able to duplicate that.
maybr I’ll try disconnecting the connector and doing the grease and see what that gets me.
any other newly learned things with this? Is it a wiring issue or a poorly designed sensor issue do you think?
12-08-2018, 12:56 PM
#105
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Well dammit. I reached up to disconnect the electrical connector thinking I would just disconnect it and reconnect it and see if I got any different results. And wouldn’t you know I can’t get the connector back on the sensor. Seems like the damn pins aren’t lining up and I can’t get enough leverage one handed to maneuver it. 😡
01-19-2021, 10:58 AM
#107
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01-19-2021, 11:10 AM
#108
I was wondering if anyone else is having the same problem as me with the capless fuel filler. Seems like everytime I get gas recently, the check engine light comes on within a few days. Code P0451; Evap Emission Control System Pressure Sensor Performance. This is on a 2011 5.0 with 18K on it btw. Talked to Ford service. First guy told me the gas cap was not tight. After I told him there is no cap another service employee told me to take the funnel and work the door a bit as there could be dirt holding the door open enough to trip the light. Did this and after two to four cold starts the light is off. This happened a couple more times to me. Worked the funnel and light goes away.
So I filled up on Sunday and when I was done I put the nozzle in and out a few times to work the door. After more than a few puzzled looks from other customers I went home. Today after work the dang light is on again with the same code....0451. So I funnel-banged my truck for a fourth time. I'm taking my truck to my normal mechanic in a few days for PA safety and emmissions inspection. It will fail the emmissions portion if there are any trouble codes stored or the CEL is on. Thats not what I'm worried about. What concerns me is that the friggin light will come on every two weeks after I fill up.
Anyone else having issues with this and if so, what did you do about it? I haven't gone back to Ford yet because I wanted to see if someone here is dealing with the same thing. Gives me ammo so to speak when I talk to Ford (worked when I was having Sync issues).
Thanks
So I filled up on Sunday and when I was done I put the nozzle in and out a few times to work the door. After more than a few puzzled looks from other customers I went home. Today after work the dang light is on again with the same code....0451. So I funnel-banged my truck for a fourth time. I'm taking my truck to my normal mechanic in a few days for PA safety and emmissions inspection. It will fail the emmissions portion if there are any trouble codes stored or the CEL is on. Thats not what I'm worried about. What concerns me is that the friggin light will come on every two weeks after I fill up.
Anyone else having issues with this and if so, what did you do about it? I haven't gone back to Ford yet because I wanted to see if someone here is dealing with the same thing. Gives me ammo so to speak when I talk to Ford (worked when I was having Sync issues).
Thanks
03-13-2022, 08:53 AM
#110
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