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P0446 = evaporative emissions vent system performance. So my scanner shows the following...
EVAP vent solenoid command is venting,
EVAP Purge solenoid command: value = 0, range 0 to 100%
Fuel Tank Pressure sensor: value = - 4.36, range -4.27 to 33 KPa, so I'm off by 0.09 KPa, the only thing that is off.
Fuel Tank Pressure sensor: value = 4.8 V, range 0 to 5 V
From what I found on the net for a P0446, looks like I have to replace the fuel pressure sensor.
Does this mean I have to remove one or both fuel tanks? No reference to this in the Shop Manual. Let me know if there is a reference to this.
Can't find anything in the Shop Manual regarding fuel sensors or their removal. Anyone have a page number, please let me know.
It's been one thing after another. Should have never sold my Mustang!
Thanks in advance.
What manual are you using…a Haynes ??…it is in my hard copy service manual…you will have to remove the right rear tire to access the sensor through a removable panel…do you have a bidirectional scan tool where you can do a purge/seal to confidently diagnose that sensor ??…on most GM’s you should read around 1.5 volts on the sensor if the tank is vented to atmosphere…if yours is not near this value just remove the gas cap…doing a purge/seal you can open the purge valve and close the vent valve which pulls the tank into a vacuum…at the end of the test when the vent valve opens and the tank is quickly vented to atmosphere you should see the 1.5 volts again…pic was on my 2001…now you may have something like a stuck closed vent valve or a clogged canister if you fill up your tank to the top of the fill pipe…so I hope you guessed right…to the right of the access cover you can see part of the canister.
I’ve reread your post and I saw you were reading 4.8 volts on the scan tool so you are reading the 5 volt reference as seen on the wiring diagram…you will need to measure some voltages on that 3 wire sensor just to make sure it is not a wiring problem as this is basically a simple potentiometer…you need to unplug the sensor to measure it.
I listened to your advice for a previous problem and bought an Autel MX 808, I’m pretty sure it is not bidirectional. I started my Vette and hooked up the Autel, checked the reading for the fuel tank pressure sensor, the readings were the same as yesterday, I then removed the gas cap waited for a few minutes, no change, increased the RPM to 1500, still no change, fuel tank pressure sensor values of -4.36 KPa and 4.8 V. The manual I’m using is Service Manual, 2002 Chevrolet Corvette, consists of 3 volumes, about 1 ¼ inches thick, cost me over $500.00. I’ve triple checked the index for any mention of gas tank, tank, fuel tank, fuel cell, I couldn’t think of any other wording to refer to the fuel system. I’m sure somewhere in the thousands of pages, it is mentioned but how GM refers to it I’ve no idea. Do you mind giving me the page number where you found it. I am thinking of getting a Haynes Manual, their Table of Contents does show Fuel Systems. Thanks for suggesting Schrodingers Box, I’ve watched over 20 episodes. Matt is an excellent teacher. My next step is to measure voltages on the 3 wire sensor. I’ll get back to you once that is done. Thanks again for all of your help.
With your Autel if you see “output controls” its bidirectional…if you see 4.8 you are seeing the 5 volt reference…unplug sensor and with key on see what the FTP sensor voltage shows…with DVOM you should see 5-0-0 sensor unplugged…5 volt reference and 0 on signal and low reference…measure voltage from 5 volt reference to low reference and you should see 5 volts…if you are 0 volts with scan tool on FTP sensor data PID take a jumper wire and go from 5 volt reference to SIGNAL…scan tool should see your 4.8…if you see all that it’s a bad sensor…I think in my 3 volume book its page 6-593 but I’ll check later…look for fuel tank pressure sensor under F in the index…Matt is sharp…I have him my old 2 channel PicoScope and he said it’s changed his channel !!
With your Autel if you see “output controls” its bidirectional…if you see 4.8 you are seeing the 5 volt reference…unplug sensor and with key on see what the FTP sensor voltage shows…with DVOM you should see 5-0-0 sensor unplugged…5 volt reference and 0 on signal and low reference…measure voltage from 5 volt reference to low reference and you should see 5 volts…if you are 0 volts with scan tool on FTP sensor data PID take a jumper wire and go from 5 volt reference to SIGNAL…scan tool should see your 4.8…if you see all that it’s a bad sensor…I think in my 3 volume book its page 6-593 but I’ll check later…look for fuel tank pressure sensor under F in the index…Matt is sharp…I have him my old 2 channel PicoScope and he said it’s changed his channel !!
Thanks again. I checked everything I could see including the icons top and bottom of the screen, nothing mentioned wrt "output controls". I checked the Index under "F", it lists Fuel Filler Door, Pocket and Rail. There is nothing else listed preceded by the word Fuel. I have to put the electrical testing on hold until Friday, will contact you then.
Thanks for the video. Definitely will be careful checking the sensor voltage. According to the net, I have the bidirectional feature. I've emailed Autel re directions on how to find it.
I'll be all over the FTP sensor Fri. Happy Thanksgiving!
Thanks for the video. Definitely will be careful checking the sensor voltage. According to the net, I have the bidirectional feature. I've emailed Autel re directions on how to find it.
I'll be all over the FTP sensor Fri. Happy Thanksgiving!
I get you an answer tomorrow…best thing is just to use all the functions of the scan tool to get familiar.
This is the path to turn your cooling fan output control on and off !!…under active tests you can also find “EVAP Purge/Seal”….vent valve will close and purge valve will open drawing the tank into a vacuum…how fast the vacuum decreases will tell the PCM if you have a large or small leak…when the vent valve opens the PCM will determine how fast the tank goes to atmospheric pressure (1.5 volts).
Thanks for the pics. With my Autel Maxicheck MX808S I can get to "Power Train" (but not to Engine Module), from there to "Engine Live Data" from there I can get to both "Fuel Tank Pressure Sensors"
which will show me a live graph, highlighting Fuel Tanks Pressure Sensor gives me the options of: tachometer, duplicating the graph, horizontal measure and trigger setting plus 2 others that help even less.
I called Autel today but they are closed. I will call them on Friday morning before I get rolling on the fuel tank pressure sensor replacement. Enjoy the turkey.
I got the old FTP sensor out no problem but Amazon sent me the wrong part. Should be able to finish the job on Monday. Did not check the voltage on the old FTP sensor, too crowded in there and did not want to risk
accidentally connecting the 5 volts to ground. I'll get back to you once the new part is installed and tested.
I got the old FTP sensor out no problem but Amazon sent me the wrong part. Should be able to finish the job on Monday. Did not check the voltage on the old FTP sensor, too crowded in there and did not want to risk
accidentally connecting the 5 volts to ground. I'll get back to you once the new part is installed and tested.
I would stay away from buying these sensors from Amazon or EBay…I’d try Rock Auto or Napa if there is one near you.
If at all possible, I try to buy made in the USA, unfortunately not always available.
The sensor I ordered from Amazon has the same part no. as the original AC Delco and it is made in Singapore, Malaysia. At least it is not made in China.
Got a P0446 H C code, how to proceed?
