2004 Ford Mustang V6 3.9L OBD2 Codes P1000 and P0455 (x2)

Hello everyone! I'm fairly new to StangNet.com and I'm getting used to posting things online. I have another thread about my Motor Oil or Transmission Fluid Leak, but I got no replies to that thread. Not sure how I posted it on the site, but it still shows up. Here's the link if interested (https://www.stangnet.com/mustang-fo...-v6-leaking-fluid-or-oil.917994/#post-9261286).

For this new issue I'm having I'm getting three (3) codes on my Bosch OBD2 Scanner (1 ODBII/EOBD & 2 ECM). I need to do a smog test in California and was told it will not pass until these are fixed.

The 1st is the P1000 (On Board Diagnostics II Monitor/Drive Cycle Test Not Complete NON-MIL). The top reported fix is...Performed Emission Monitor Drive Cycle Until Drive Cycle Monitor Reports All Supported Monitors are OK. I originally cleared all the codes and then drove the car over 100 miles on the freeway and streets nonstop, but the codes are still there.

The 2nd is the P0455 (Evaporative Emission System Leak Detected (Gross Leak/No Flow PENDING). The top reported fix is...Replaced Evaporative Emissions (EVAP) Canister Purge Solenoid/Valve. I replaced the fuel cap with the original Ford Motorcraft gas cap and the fuel cap light on the dashboard came off (went away), but this code is still here after driving 100+ miles. I did buy a used gas cap from the salvage yard. I'm guessing it's good since the fuel cap light came off the dashboard, but I'm contemplating just buying a new one from Ford Motorcraft just to be 100% sure it works.

The 3rd is another P0455 (Evaporative Emission System Leak Detected (Gross Leak/No Flow PENDING). The top reported fix is...Replaced Evaporative Emissions (EVAP) Canister Purge Solenoid/Valve. Since I've already driven 100+ miles and these three (3) codes are still on the computer I'm looking to replace the EVAP Canister Purge Solenoid/Valve. I called three (3) different Ford Dealerships and they all tell me different things. One said the EVAP Canister Purge Solenoid/Valve system is made-up of three (3) different part numbers for Motorcraft (9C915, 9D653 and 9F945). Another told me there's only one (1) part and that is Motorcraft (CX9216). The last one told me it's Motorcraft part number CX1692.

I want to buy the correct part, but need to know where this is located so I can get the right one. All of them told me it's in the engine compartment somewhere near the firewall. I want to take it off and take it with me when I buy the new one to make sure it's exactly the same one since all of them gave me different parts. There's currently no check engine light or any other light on the dashboard at the moment, but these 3 codes are showing up on my OBD2 scanner tool.

Any thoughts? Thank you all for your assistance and support!
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SN Certified Technician
Aug 14, 2009
Houston Texas
First. Should we assume this a a 1999-2004 model year Mustang?

Before you go crazy replacing parts there are two things to check.

Check the EVAP vapor hose from the throttle body to the right hand fender well for leaks.

Next check the gas tank filler neck for rust through.
Thanks for your reply and suggestions. Here's the update...

Yes, this is a 2004 Ford Mustang V6 3.9L. I have replaced the EVAP Canister Purge Valve, the EVAP Canister Vent Solenoid and ended up buying a brand new Ford Motorcraft Fuel Cap (Gas Cap) to replace the used one I bought at the junk yard. The P0455 codes still came back after replacing these parts and after 150+ miles of driving and have been told to replace the Fuel Tank Pressure Sensor (FTP Sensor).

Based on your comments, I did check the Gas Tank Filler Neck for rust through and it didn't have any; it was pretty clean compared to some I've seen online (YouTube, etcetera). Before I replace the FTP Sensor I will check the EVAP vapor hose from the throttle body to the right hand fender well for leaks.

I will keep everyone here updated and thanks again for your recommendations.
I replaced the EVAP vapor hose from the throttle body to the EVAP Canister Purge Valve. It was deteriorated pretty bad and coming apart in my hands. I also replaced the other hoses/lines from the EVAP Canister Purge Valve to various lines in the car. I also decided to replace the EVAP Charcoal Canister. Now I'm getting a P0457 code along with the P1000 and the check fuel cap light is back on. The P0455 code is gone now, but I'm getting a new P0457 code. I got the P0457 code back in September 18, 2020 but after replacing the fuel cap with an original Ford Motorcraft used (junkyard) it went away and the P0455 code started to appear. I've since bought a brand new Ford Motorcraft fuel cap.

Here's the update of what I've replaced.
1. EVAP Canister Purge Valve - (Brand New - Duralast)
2. EVAP Canister Vent Solenoid - (Brand New - Ford Motorcraft)
3. EVAP Charcoal Canister - (Brand New - Ford Motorcraft)
4. Fuel Filler Cap (Gas Cap) - (Brand New - Ford Motorcraft)
5. EVAP hoses/lines from the EVAP Canister Purge Valve to the engine - (Brand New - Ford Motorcraft)

I've been told to replace the Fuel Tank Pressure (FTP) Sensor and the Fuel Filler Neck.

Any thoughts or recommendations from anyone?


SN Certified Technician
Aug 14, 2009
Houston Texas
I've been told to replace the Fuel Tank Pressure (FTP) Sensor and the Fuel Filler Neck.
Who ever told you that as a trouble shooting method isn't doing you any favors. IMO you would be a TON smarter to TEST the fuel pressure sensor to find out if it's bad before going to the trouble of replacing it.

Besides after you dropped the tank you would find out that replacing the fuel tank pressure sensor is easier said than done.

So how to test? Use an ODB2 scanner to monitor the fuel tank pressure while the car is operating. Here's some information on an affordable ODB2 scanner. Likely the cost of the USB dongle would have already paid for itself by not replacing good parts.

The other HUGE advantage that an advanced function ODB2 scanner can give you is the ability to perform a bay test of the EVAP system using bi-directional control.

ForScan ODB2 scanner w ELM327 USB​

Thanks for your reply and explanation. I would love to know how to use the OBD2 scanner correctly and to pinpoint the problem. I have a Bosch OBD1200 Scanner and this is the one I used to diagnose the problem (P0455 & P0457), but I based it on the CODECONNECT fixes. For example: #1 Fix = Replace EVAP Canister Purge Valve, #2 Fix = Replace FTP Sensor, #2 Fix...Etcetera. How would I use it to pinpoint the pressure of the FTP sensor, fuel filler neck, etcetera? Are there specific PID's to run while driving or is there another menu inside the scanner to look at? I did access some TEST $04, TEST $63 screens (I've included the screenshots), but I didn't capture them while driving. In the meantime I will try to read more about how to use the Bosch OBD1200 scanner to measure the FTP sensor and the fuel filler neck or other problem. Thanks once again for your insight and assistance.
Here's the screenshots...


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SN Certified Technician
Aug 14, 2009
Houston Texas
How would I use it to pinpoint the pressure of the FTP sensor, fuel filler neck, etcetera?
One way to test the fuel tank pressure sensor is to long term graph the FTP PID value. Does it ever change?

Another way is to use the bi-directional capability to close the CV vent solenoid and then opening the EVAP VMV while the engine is running. What should this do? This should subject the gas tank to engine vacuum. What should the FTP sensor do? At the minimum it should CHANGE. If the EVAP system is reasonably air tight then the FTP should drop. When the FTP sensor acts as expected, this "proves" it is working at some level.

A broken FTP sensor would likely graph as a "flat line".
I wasn't able to find a FTP (Fuel Tank Pressure) screen or graph on my OBD2 scanner. The only thing that came close was the "Relative Fuel Rail Pressure - REL FRP (PSI)" and when I turned on the key, but left the engine off it read 41.56 PSI and this was at 2:07PM. It then started to drop little by little until it reached 18.34 PSI at 2:47PM (exactly 30 minutes later). This happened all while the engine was off and the key was in the on state. While I was driving it stayed between 38-41 PSI for the REL FRP (PSI). Other readings I took were for the "Fuel Trim Bank/Sensor" for "ST FTRM11(%)" & "ST FTRM21(%)" & "ST FTRM1(%)" & "ST FTRM2(%) while driving (see screenshots). I've also included the "TEST $04" results since these were the only ones that came back showing "LOW" while all the others were "OK" I have also included pictures of the Fuel Filler Neck where it connects to the gas tank and where you pump the gasoline to see if anything looks strange to anyone. I've been told by some people to do a SMOKE TEST to check for leaks. Any thoughts on the information I've provided so far? Does anyone know what this "TEST $04" is since this is the only one that had "LOW" measurements on it? What else should I do or check? The P0457 & P1000 codes are still present along with the "Check Fuel Cap" light the dashboard and I've driven 150+ miles. All your thoughts and information is greatly appreciated.


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Here's the additional pictures...


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There's a lot of pictures that will hopefully help. Thanks.


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I went to a local auto repair shop and had them run a complete diagnostic test along with the pressure test. They hooked up the pressure machine to the EVAP connection in the hood (close to the EVAP Canister Purge Valve) and it maintained the pressure (the bubble-thing stayed in the middle). The mechanic told me that means there's no leaks anywhere in the EVAP system of hoses, fuel tank, etcetera. He then hooked up this large tablet/OBD2 scanner to the car and told me the FTP sensor was defective, because it was way off (the readings were wrong). So the problem is the FTP sensor, but the part is discontinued everywhere (Ford dealerships, local auto parts, specialty auto parts, everywhere). The mechanic told me the best option was to get one from the junk yard and pay to put it on. I researched heavily online and found a brand new one from DORMAN Part# 911-260 that many people online claim is a compatible fix, but the hoses needed to be cut in order to adapt it to the FTP sensor assembly hoses on top of the fuel tank. I bought the new sensor and had another local mechanic put it on, but now I'm getting a P1450 error code on my OBD2 scanner which is "Fuel Tank Vacuum Can Not Bleed" The local mechanic told me that our best option is to buy the one from the junkyard and hope that works. Any thoughts from anyone on this site regarding the P1450 error code and the FTP sensor or anything else? I've gone through a lot with this car and it won't pass the SMOG test here in California. Kindly help and all your thoughts, input or recommendations are greatly appreciated. I included the picture of the new sensor installed on my gas tank.


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