fuel pump replacement
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Joined: 01-23-2009
Posts: 26,532
From: Fredericksburg,VA
Here is a pdf of the article in Mitchell OnDemand
It is a matter of the sensor not zeroing when P0442 is run. It has to start at zero so that the computer knows what the atmospheric pressure is. There is a reference port that needs to be open. Could be the canister is clogged. Could be either the 5V ref or the low ref is not good. Test the low ref by thinking of it as ground, check continuity to ground.
p0451-p0454.pdf
It is a matter of the sensor not zeroing when P0442 is run. It has to start at zero so that the computer knows what the atmospheric pressure is. There is a reference port that needs to be open. Could be the canister is clogged. Could be either the 5V ref or the low ref is not good. Test the low ref by thinking of it as ground, check continuity to ground.
p0451-p0454.pdf
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Member
Joined: 05-27-2015
Posts: 95
From: N. America
Here is a general reply to my on going problem which again started after I changed the fuel tank and fuel pump due to a bad leak at the top of the tank at the
vent hose fittings on the tank. Also when looking at the scanner it had NO history of problems at all. Again the ONLY problem code PO451 was not showing ever
before changing the tank and pump? The good part is there are no running problems in driving. It takes times for me to get to a lift and scanner so work as I can.
So I push on and thank all for the help....
================================================== ================================================= E-VAP System Problems
WARNING LIGHTShttps://www.carparts.com/blog/can-a-...=65&bsft_tv=47
Can a Loose Gas Cap Turn On The Check Engine Light?
The engine computer, which is often referred to as the powertrain control module (PCM), monitors the EVAP system for leaks. If the PCM detects a leak—from a loose gas cap or any other part of the EVAP system—it turns on the CEL and stores a corresponding diagnostic trouble code (DTC) in its memory.
How to Tell If a Loose Fuel Cap Is Triggering Your Check Engine Light
To determine whether the gas cap might be to blame, you’ll first need to use a scan tool or code reader to retrieve the DTCs from the PCM’s memory.
Typically, when the gas cap is to blame for the CEL, the PCM stores a code for an EVAP system leak in its memory. Examples include codes P0455 “Evaporative Emission System Leak Detected (Large Leak)” and P0457 “Evaporative Emission System Leak Detected (Fuel Cap Loose/Off)”.
How to Reset the Check Engine Light on a Loose Gas Cap
Although the PCM can log EVAP leak codes for a variety of reasons, the most common cause is a loose or faulty gas cap. As such, you’ll want to check the gas cap before trying anything else. Make sure to tighten the cap completely. On most vehicles, the cap will “click” into place when it’s secure.
After you’ve tightened down the gas cap, use a scan tool or code reader to clear the EVAP-related codes from the PCM’s memory.The codes will not go away immediately on their own—you must use a tool to clear them. Then you can drive the vehicle to see whether the codes return.
If the CEL does not return after a few weeks of driving, there’s a good chance that tightening down the gas cap fixed the problem.
You can verify whether tightening the gas cap fixed the problem by watching the EVAP monitor on a scan tool (some code readers will also work).
It’s important to note, however, that the PCM does not continuously check the EVAP system for leaks. Instead, the device only runs the EVAP system self-test, which is referred to as a “monitor”, when certain conditions are correct. For example, on most vehicles, the fuel tank must be between 15% and 85% full, and several sensors must be within a certain operating range.
Once the EVAP monitor’s status changes to “OK” (or something similar), the PCM has deemed the problem is fixed.
You can verify whether tightening the gas cap fixed the problem by watching the EVAP monitor on a scan tool (some code readers will also work). Once the EVAP monitor’s status changes to “OK” (or something similar), the PCM has deemed the problem is fixed.
Keep in mind that you may need to drive the car for several days (or even weeks) before the PCM runs the EVAP system monitor.
What If the Gas Cap is Not the Cause of the EVAP Leak Code?
If the EVAP leak code returns after tightening down the gas cap, you may want to try swapping out the cap, since replacements are relatively inexpensive. Should you find the code returns even after replacing the cap, the leak is somewhere else in the EVAP system.
Pinpointing an EVAP leak that’snotthe gas cap can be difficult. Usually, the process requires the use of a professional smoke machine, which forces smoke into the EVAP system so that (hopefully) the leak will become visible when smoke starts billowing out.
vent hose fittings on the tank. Also when looking at the scanner it had NO history of problems at all. Again the ONLY problem code PO451 was not showing ever
before changing the tank and pump? The good part is there are no running problems in driving. It takes times for me to get to a lift and scanner so work as I can.
So I push on and thank all for the help....
================================================== ================================================= E-VAP System Problems
WARNING LIGHTShttps://www.carparts.com/blog/can-a-...=65&bsft_tv=47
Can a Loose Gas Cap Turn On The Check Engine Light?
The engine computer, which is often referred to as the powertrain control module (PCM), monitors the EVAP system for leaks. If the PCM detects a leak—from a loose gas cap or any other part of the EVAP system—it turns on the CEL and stores a corresponding diagnostic trouble code (DTC) in its memory.
How to Tell If a Loose Fuel Cap Is Triggering Your Check Engine Light
To determine whether the gas cap might be to blame, you’ll first need to use a scan tool or code reader to retrieve the DTCs from the PCM’s memory.
Typically, when the gas cap is to blame for the CEL, the PCM stores a code for an EVAP system leak in its memory. Examples include codes P0455 “Evaporative Emission System Leak Detected (Large Leak)” and P0457 “Evaporative Emission System Leak Detected (Fuel Cap Loose/Off)”.
How to Reset the Check Engine Light on a Loose Gas Cap
Although the PCM can log EVAP leak codes for a variety of reasons, the most common cause is a loose or faulty gas cap. As such, you’ll want to check the gas cap before trying anything else. Make sure to tighten the cap completely. On most vehicles, the cap will “click” into place when it’s secure.
After you’ve tightened down the gas cap, use a scan tool or code reader to clear the EVAP-related codes from the PCM’s memory.The codes will not go away immediately on their own—you must use a tool to clear them. Then you can drive the vehicle to see whether the codes return.
If the CEL does not return after a few weeks of driving, there’s a good chance that tightening down the gas cap fixed the problem.
You can verify whether tightening the gas cap fixed the problem by watching the EVAP monitor on a scan tool (some code readers will also work).
It’s important to note, however, that the PCM does not continuously check the EVAP system for leaks. Instead, the device only runs the EVAP system self-test, which is referred to as a “monitor”, when certain conditions are correct. For example, on most vehicles, the fuel tank must be between 15% and 85% full, and several sensors must be within a certain operating range.
Once the EVAP monitor’s status changes to “OK” (or something similar), the PCM has deemed the problem is fixed.
You can verify whether tightening the gas cap fixed the problem by watching the EVAP monitor on a scan tool (some code readers will also work). Once the EVAP monitor’s status changes to “OK” (or something similar), the PCM has deemed the problem is fixed.
Keep in mind that you may need to drive the car for several days (or even weeks) before the PCM runs the EVAP system monitor.
What If the Gas Cap is Not the Cause of the EVAP Leak Code?
If the EVAP leak code returns after tightening down the gas cap, you may want to try swapping out the cap, since replacements are relatively inexpensive. Should you find the code returns even after replacing the cap, the leak is somewhere else in the EVAP system.
Pinpointing an EVAP leak that’snotthe gas cap can be difficult. Usually, the process requires the use of a professional smoke machine, which forces smoke into the EVAP system so that (hopefully) the leak will become visible when smoke starts billowing out.
Moderator
Joined: 01-23-2009
Posts: 26,532
From: Fredericksburg,VA
P0451 has nothing to do with the actual pressure in the tank. It is the inability of the pressure sensor to zero itself due to either an electrical connection or a blocked vent system, so that it cannot reliably measure the pressure. It needs to be sensing the same pressure inside the tank as outside the tank before P0442 can run
When the P0442 test starts to run it tells the pressure sensor to zero itself, that is the P0451 test. The P0442 tests the rate of change in the vapor pressure in the tank after the engine is turned off.
Is it possible that the charcoal canister got disturbed or any of the tubes around it got kinked? Is it possible that the connectors to the pressure sensor got switched? I think I recall someone having a problem with the tank connectors being different.
When the P0442 test starts to run it tells the pressure sensor to zero itself, that is the P0451 test. The P0442 tests the rate of change in the vapor pressure in the tank after the engine is turned off.
Is it possible that the charcoal canister got disturbed or any of the tubes around it got kinked? Is it possible that the connectors to the pressure sensor got switched? I think I recall someone having a problem with the tank connectors being different.
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