p0451
03-22-2013, 06:48 PM
#1
Nut up or shut up
Thread Starter
p0451
So I was warming up my engine today before going home from work and my CEL was on. So I checked my edge for the code and it was p0451. How bad would it be to drive on it or erase the code? Is this serious? I talked to AAMCO and they gave me some sort of outrageous price of like $95 an hour and it could take a whole day..Going to call the dealership later.
04-01-2018, 09:13 AM
#4
05 5.4l 3v s.crew lariat
Check for cracked hoses ,bad gas cap etc ,lot of lines in this circuit .
Too many people want to shoot the sensor instead of looking for a problem . You can make up your own cheap smoke machine too find leaks . Evap system to capture gas fumes in charcoal canister to be burned later as computer tells it to .
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amtpdb1 (04-02-2018)
04-01-2018, 10:32 AM
#5
LightningRod
Challange the sensor!
I agree with @redfishtd. This seems headed for another one of those parts throwing parties -- (that I would not want to attend at $300 the first pop). Trust what the PCM is telling you. AND REMEMBER: the PCM 'NEVER' tells you to replace a sensor. P0451 says "Evaporative Emission Control System Pressure Sensor Range/Performance". The attached diagnostic reference chart shows FTP (fuel tank pressure) should read between 2.62 volts Key on Engine Off to somewhere around 1.53 when the purge valve is pulling maximum negative pressure in the tank (ie -0.27 psi, ~ -7 to -10 In H2o).
A bad conection at the PCM wiring harness plug, -OR- in the Reference Voltage line, common, or signal wire -OR- Short on one of them to the sensor itself, would definately "FOOBAR" those readings 'OUT OF RANGE'. With the aid of the attached Wiring Diagram, you should be able to verify if it's some inexpensive fix like that or if it truely is a failed sensor.
At KOEO, both the purge valve (on the firewall) AND the Canister Vent solenoid (underneath by Canister) is CLOSED - which means the tank is sealed. You remove gas cap and can put a piece of radiator hose on the tank filler neck - and BLOW / SUCK on it and see if the voltage reading at relevant points changes.
Also, If you can specify PID # and formulas in your Edge OBDII code reader permits you to specify PID / Formula information, you can read both FTP Volts and FTP pressure in pascals at PID# 1639 - (A*256+B)/13107, and PID # 1687 - Signed(A)*256+B, respectively. By doing this, you can see the the readings respond dynamically when you BLOW/SUCK on the fuel tank neck - IF the sensor & wiring are all functioning properly.
Hope this saves you $300. If it does you can buy me a beer!
LOL
-------------------- BTW. The PCM plugs shown on the Diagnostic Reference Chart are shown (mirrored) as viewed from inside the cab! Also - it indicates FTP is on plug B-65, and note that that does not match the wiring diagram - so verify wire colors in the harness
A bad conection at the PCM wiring harness plug, -OR- in the Reference Voltage line, common, or signal wire -OR- Short on one of them to the sensor itself, would definately "FOOBAR" those readings 'OUT OF RANGE'. With the aid of the attached Wiring Diagram, you should be able to verify if it's some inexpensive fix like that or if it truely is a failed sensor.
At KOEO, both the purge valve (on the firewall) AND the Canister Vent solenoid (underneath by Canister) is CLOSED - which means the tank is sealed. You remove gas cap and can put a piece of radiator hose on the tank filler neck - and BLOW / SUCK on it and see if the voltage reading at relevant points changes.
Also, If you can specify PID # and formulas in your Edge OBDII code reader permits you to specify PID / Formula information, you can read both FTP Volts and FTP pressure in pascals at PID# 1639 - (A*256+B)/13107, and PID # 1687 - Signed(A)*256+B, respectively. By doing this, you can see the the readings respond dynamically when you BLOW/SUCK on the fuel tank neck - IF the sensor & wiring are all functioning properly.
Hope this saves you $300. If it does you can buy me a beer!
LOL -------------------- BTW. The PCM plugs shown on the Diagnostic Reference Chart are shown (mirrored) as viewed from inside the cab! Also - it indicates FTP is on plug B-65, and note that that does not match the wiring diagram - so verify wire colors in the harness
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amtpdb1 (04-02-2018)
04-02-2018, 05:10 PM
#6
I agree with @redfishtd. This seems headed for another one of those parts throwing parties -- (that I would not want to attend at $300 the first pop). Trust what the PCM is telling you. AND REMEMBER: the PCM 'NEVER' tells you to replace a sensor. P0451 says "Evaporative Emission Control System Pressure Sensor Range/Performance". The attached diagnostic reference chart shows FTP (fuel tank pressure) should read between 2.62 volts Key on Engine Off to somewhere around 1.53 when the purge valve is pulling maximum negative pressure in the tank (ie -0.27 psi, ~ -7 to -10 In H2o).
A bad conection at the PCM wiring harness plug, -OR- in the Reference Voltage line, common, or signal wire -OR- Short on one of them to the sensor itself, would definately "FOOBAR" those readings 'OUT OF RANGE'. With the aid of the attached Wiring Diagram, you should be able to verify if it's some inexpensive fix like that or if it truely is a failed sensor.
At KOEO, both the purge valve (on the firewall) AND the Canister Vent solenoid (underneath by Canister) is CLOSED - which means the tank is sealed. You remove gas cap and can put a piece of radiator hose on the tank filler neck - and BLOW / SUCK on it and see if the voltage reading at relevant points changes.
Also, If you can specify PID # and formulas in your Edge OBDII code reader permits you to specify PID / Formula information, you can read both FTP Volts and FTP pressure in pascals at PID# 1639 - (A*256+B)/13107, and PID # 1687 - Signed(A)*256+B, respectively. By doing this, you can see the the readings respond dynamically when you BLOW/SUCK on the fuel tank neck - IF the sensor & wiring are all functioning properly.
Hope this saves you $300. If it does you can buy me a beer!LOL
-------------------- BTW. The PCM plugs shown on the Diagnostic Reference Chart are shown (mirrored) as viewed from inside the cab! Also - it indicates FTP is on plug B-65, and note that that does not match the wiring diagram - so verify wire colors in the harness
A bad conection at the PCM wiring harness plug, -OR- in the Reference Voltage line, common, or signal wire -OR- Short on one of them to the sensor itself, would definately "FOOBAR" those readings 'OUT OF RANGE'. With the aid of the attached Wiring Diagram, you should be able to verify if it's some inexpensive fix like that or if it truely is a failed sensor.
At KOEO, both the purge valve (on the firewall) AND the Canister Vent solenoid (underneath by Canister) is CLOSED - which means the tank is sealed. You remove gas cap and can put a piece of radiator hose on the tank filler neck - and BLOW / SUCK on it and see if the voltage reading at relevant points changes.
Also, If you can specify PID # and formulas in your Edge OBDII code reader permits you to specify PID / Formula information, you can read both FTP Volts and FTP pressure in pascals at PID# 1639 - (A*256+B)/13107, and PID # 1687 - Signed(A)*256+B, respectively. By doing this, you can see the the readings respond dynamically when you BLOW/SUCK on the fuel tank neck - IF the sensor & wiring are all functioning properly.
Hope this saves you $300. If it does you can buy me a beer!
LOL-------------------- BTW. The PCM plugs shown on the Diagnostic Reference Chart are shown (mirrored) as viewed from inside the cab! Also - it indicates FTP is on plug B-65, and note that that does not match the wiring diagram - so verify wire colors in the harness
04-02-2018, 05:49 PM
#7
LightningRod
Sorry I skimmed over some of that. My posts always seem to get too long anyhow. Yes it's 221639 and 221687. The '22' is Mode and the rest is PID in hexadecimal.
On the Torque dashboard screen - 'long tap' any digital gauge, then select >Display Configuration...>Number of Decimal Places, and set it to whatever you want. Torque Pro is very intuitive.
I don't think a smoke test in indicated in your case. There are several other DTCs for leak test failure, purge valve faults, canister vent problems, leak down tests, gas cap off and so forth. But THEY are all dependent on the FTP sensor working reliablely. The readings you were getting seem to be in the right range. Giggle some more wires, or unplug and spray with contact cleaner / re-plug several times and monitor it some. BTW, fuel slosh in the tank will whip up additional gas fumes and change pressure upward for a period. Some of the evap tests will 'abort' if FTP voltage is irregular assuming rough road or slosh.
On the Torque dashboard screen - 'long tap' any digital gauge, then select >Display Configuration...>Number of Decimal Places, and set it to whatever you want. Torque Pro is very intuitive.
I don't think a smoke test in indicated in your case. There are several other DTCs for leak test failure, purge valve faults, canister vent problems, leak down tests, gas cap off and so forth. But THEY are all dependent on the FTP sensor working reliablely. The readings you were getting seem to be in the right range. Giggle some more wires, or unplug and spray with contact cleaner / re-plug several times and monitor it some. BTW, fuel slosh in the tank will whip up additional gas fumes and change pressure upward for a period. Some of the evap tests will 'abort' if FTP voltage is irregular assuming rough road or slosh.
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07-26-2018, 02:37 AM
#8
F150Torqued:
I am still working on this. I pulled the line off the purge valve and connected a regulator on the test port and put 7 inches of water pressure on it and the purge valve is sealed. I did not seal the vent on the evap tank. I just left it open during the test. Torque said the pressures were all off but the voltage went from 2.2 with out pressure to 2.6 with pressure. I pulled the gas cap off during the test and Torque said that the pressure voltage dropped back to the unpressurizer figure. I will have to go to the program and see if some of these formula figures for the program are wrong as the water pressure on the program did not change hardly at all while the voltage definitely changed and the pascals just sat around -1500 or so. It was just a ruff test to see if something was plugged so I could see the voltage change. I will have to pull the tire and finish the smoke tank and complete the test. I heard that the voltage was suppose to be about 2.6 with the car off but I don't see that. I wonder if most of the sensors for fords tell the same things to the computer as far as the same numbers? I found a person selling the sensor that looks close for a 05 to 10 Ford Explorer. I wonder if I purchased it and made up connections to put it in line and fit the plug if it would work? I would think that with the same motor, 5.4l, it would work but I have no idea if it functions the same. I would hope that Ford would not re-engineer the computer function on each car each year, but what do I know. If anyone knows if I should be able to adapt it and have it work, please chime in.
Thanks
I am still working on this. I pulled the line off the purge valve and connected a regulator on the test port and put 7 inches of water pressure on it and the purge valve is sealed. I did not seal the vent on the evap tank. I just left it open during the test. Torque said the pressures were all off but the voltage went from 2.2 with out pressure to 2.6 with pressure. I pulled the gas cap off during the test and Torque said that the pressure voltage dropped back to the unpressurizer figure. I will have to go to the program and see if some of these formula figures for the program are wrong as the water pressure on the program did not change hardly at all while the voltage definitely changed and the pascals just sat around -1500 or so. It was just a ruff test to see if something was plugged so I could see the voltage change. I will have to pull the tire and finish the smoke tank and complete the test. I heard that the voltage was suppose to be about 2.6 with the car off but I don't see that. I wonder if most of the sensors for fords tell the same things to the computer as far as the same numbers? I found a person selling the sensor that looks close for a 05 to 10 Ford Explorer. I wonder if I purchased it and made up connections to put it in line and fit the plug if it would work? I would think that with the same motor, 5.4l, it would work but I have no idea if it functions the same. I would hope that Ford would not re-engineer the computer function on each car each year, but what do I know. If anyone knows if I should be able to adapt it and have it work, please chime in.
Thanks
07-27-2018, 10:13 AM
#9
LightningRod
@amtpdb1
Not sure I interpret your diagnostic procedure correctly - which line you pulled of the purge valve. If you made the FTP voltage 'rise', that suggests you were putting pressure in the tank. Let's analyze that. That shouldn't happen --- BECAUSE the Carbon Canister 'VENT' vlave (located under the spare tire) is Normally Open. Assuming the canister is not 'plugged up' (full of water from driving in too deep of water) or (the vent line plugged with a mud-dobber nest or mud from 'mudding'). The later sounds plausible if you removed the Gas Cap and the Torque Pro FTP voltage dropped back down to the 'unpressurized' value.
The PCM _ONLY_ energizes the Carbon Canister VENT valve to run an 'Evap Test'. There are 'umpteen' conditions that must be met before the PCM initiates an EVAP test. /// ie: Vehicle Speed > 40mph & < 65mph, IAT < 90º, Engine Temp > ~ 170º, Engine Load stable > ~ 30 sec, Fuel Slosh < ???, etc - etc). /// So we have every reason to believe the VENT valve should have been open. SO how did you build ANY pressure in the tank that would NOT have bled off fairly quickly. The carbon canister offers some resistance to air flow, but if you held + 7 H2o pressure on it for long, I would think you would have seen it decay. That 'decay' RATE (of negative pressure - not '+' pressure) is utilized by the PCM in EVAP Tests to determine other DTC codes involving canister and vent valve operation.
Under NORMAL operation, the PCM -- modulates the PURGE valve open variably & periodically to keep slight negative pressure and slight air flow (through VENT valve - and canister) into Intake manifold to keep gas vapors from escaping into the atmosphere.
I am unable to determine your Vehicle type/description beyond the Forum this thread is in. But there are lots of variations in OBDII assignments - even to the extent of what you suggested:
Unfortunately, I have actually found differences in PID assignments - and errors in documentation, even between like year and body models assembled at different plants.
IF you are dealing with 2004-2008 F150 style 5.4l, You can modify the Torque Pro formula on PID #1687 (FTP) to read in In H2O instead of Pascal's. (Or create another Gauge) Make the formula (Signed(A)*256+B)*0.0040146307866177 to convert the PCM's Pascal output into inches of water. Min/Max should be +5 to -30.
I have worked out a complete EVAP diagnostic dashboard for Torque. I will try to return and post the PIDs / formulas and a 'csv' download file when I have a chance.
Not sure I interpret your diagnostic procedure correctly - which line you pulled of the purge valve. If you made the FTP voltage 'rise', that suggests you were putting pressure in the tank. Let's analyze that. That shouldn't happen --- BECAUSE the Carbon Canister 'VENT' vlave (located under the spare tire) is Normally Open. Assuming the canister is not 'plugged up' (full of water from driving in too deep of water) or (the vent line plugged with a mud-dobber nest or mud from 'mudding'). The later sounds plausible if you removed the Gas Cap and the Torque Pro FTP voltage dropped back down to the 'unpressurized' value.
The PCM _ONLY_ energizes the Carbon Canister VENT valve to run an 'Evap Test'. There are 'umpteen' conditions that must be met before the PCM initiates an EVAP test. /// ie: Vehicle Speed > 40mph & < 65mph, IAT < 90º, Engine Temp > ~ 170º, Engine Load stable > ~ 30 sec, Fuel Slosh < ???, etc - etc). /// So we have every reason to believe the VENT valve should have been open. SO how did you build ANY pressure in the tank that would NOT have bled off fairly quickly. The carbon canister offers some resistance to air flow, but if you held + 7 H2o pressure on it for long, I would think you would have seen it decay. That 'decay' RATE (of negative pressure - not '+' pressure) is utilized by the PCM in EVAP Tests to determine other DTC codes involving canister and vent valve operation.
Under NORMAL operation, the PCM -- modulates the PURGE valve open variably & periodically to keep slight negative pressure and slight air flow (through VENT valve - and canister) into Intake manifold to keep gas vapors from escaping into the atmosphere.
I am unable to determine your Vehicle type/description beyond the Forum this thread is in. But there are lots of variations in OBDII assignments - even to the extent of what you suggested:
IF you are dealing with 2004-2008 F150 style 5.4l, You can modify the Torque Pro formula on PID #1687 (FTP) to read in In H2O instead of Pascal's. (Or create another Gauge) Make the formula (Signed(A)*256+B)*0.0040146307866177 to convert the PCM's Pascal output into inches of water. Min/Max should be +5 to -30.
I have worked out a complete EVAP diagnostic dashboard for Torque. I will try to return and post the PIDs / formulas and a 'csv' download file when I have a chance.
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amtpdb1 (08-01-2018)
08-01-2018, 11:42 PM
#10
F150Torqued
I guess I was not clear. I pulled the vacuum line off the purge valve and connected a hose from the smoke can and pressurized the system to 7 inches of water. It stayed there as the air continued to flow out of the evap canister as I did not seal it as I need to take out the tire to get to it. I pulled off the gas cap to see if the air was getting to the tank as this was a diy smoke can I was just getting set up. The program torque was saying the tank was pressurized to .5 inches and the voltage was 2.2 before I turned on the compressor. The water pressure in the tank moved but not much with the setting I have in torque. The voltage moved to 2.5-2.6 and the pascals changed but were setting at about -1800 when pressurized. This was a quick test just for the new smoke tester. This showed that at least the formulas in torque that I have seem to be wrong for the water pressure and the pascals I be-leave. I will compare the formulas you gave me to what is in my tablet. I was thinking about cutting the FTP sensor out of the vent line and see if I could see anything. It has been too hot to lay on the concrete to get under the truck to cut it out! I ordered a sensor for a different ford with the same engine to test to see if Ford kept the same computer perimeters for the FTP sensor but sent it back as I was not sure the sensor worked the same and I was going to have to cut into the wires as the plug was not the same. When it cools down I will cut it out. I can't seem to locate a wrecking yard with a 04 F150 around anywhere around Southern Cal. I see alot of the trucks and SUVs on the road but I can't find anywhere they have parts for one in a wrecking yard. Thanks for everything and I will let you know if I find anything out! I was looking for a low cost scanner that will let you seal the evap system, but haven't seen any that do it that people are recommending. O well, thanks again.
I guess I was not clear. I pulled the vacuum line off the purge valve and connected a hose from the smoke can and pressurized the system to 7 inches of water. It stayed there as the air continued to flow out of the evap canister as I did not seal it as I need to take out the tire to get to it. I pulled off the gas cap to see if the air was getting to the tank as this was a diy smoke can I was just getting set up. The program torque was saying the tank was pressurized to .5 inches and the voltage was 2.2 before I turned on the compressor. The water pressure in the tank moved but not much with the setting I have in torque. The voltage moved to 2.5-2.6 and the pascals changed but were setting at about -1800 when pressurized. This was a quick test just for the new smoke tester. This showed that at least the formulas in torque that I have seem to be wrong for the water pressure and the pascals I be-leave. I will compare the formulas you gave me to what is in my tablet. I was thinking about cutting the FTP sensor out of the vent line and see if I could see anything. It has been too hot to lay on the concrete to get under the truck to cut it out! I ordered a sensor for a different ford with the same engine to test to see if Ford kept the same computer perimeters for the FTP sensor but sent it back as I was not sure the sensor worked the same and I was going to have to cut into the wires as the plug was not the same. When it cools down I will cut it out. I can't seem to locate a wrecking yard with a 04 F150 around anywhere around Southern Cal. I see alot of the trucks and SUVs on the road but I can't find anywhere they have parts for one in a wrecking yard. Thanks for everything and I will let you know if I find anything out! I was looking for a low cost scanner that will let you seal the evap system, but haven't seen any that do it that people are recommending. O well, thanks again.