I've been throwing parts at a P0446 code on my 2001 Blazer ZR2 for a couple of months. Changed Gas cap, Vent Valve, Purge Valve and Vent Solenoid. I removed and blew out the Charcoal Canister and blew out all the lines attached to all the parts I replaced. The code just keep coming back a day after I clear it. I'm out of ideas. Can anyone help?

 

P0446 is a malfunction in the EVAP Vent Control Circuit. The link below will take you to the flow chart, straight out of the GM factory shop manual. If you follow it exactly as written, you'll find the problem. https://blazerforum.com/forum/diagno...plained-35143/

EDIT: If the fuel pump module has been replaced with anything other than AC Delco or Delphi, the fuel tank pressure sensor might be the problem, (aftermarket modules use cheezy sensors). Also, make sure you have battery voltage on the pink wire at the vent solenoid when the ignition is in the RUN position.

 

Thanks for the information. I have replaced the fuel pump unit. I'll have to pull the fuel tank and look at again. Think I'll just replace the tank sensor at the same time. Thanks again.

 

If you replace the sensor, use an AC Delco and replace the seal, don't reuse the old one. While you've got the tank down, check the wiring at the sensor.
Unplug the electrical connector from the sensor:
Resistance on the black wire to ground must be 5 ohms or less.
With the ignition in the RUN position the grey wire should show ~5VDC.

EDIT:
The EVAP monitor also uses fuel level sensor data during the test. Some, not all, aftermarket fuel pump modules have also been known to have "issues" with the buffer in the level sensor. If you're experiencing fuel gauge problems, P0446 will likely set. Yet another reason to use AC Delco fuel pump modules

 

I agree with captain hook- and make sure the lines going to the charcoal canister are intact. One of mine rusted through above the drivers side rear wheel well- I replaced the whole line from the purge solenoid to the charcoal canister with 12' of 1/4" rubber fuel line.

 

I'm going to replace the fuel pump assembly this weekend. It's still under warranty so I'm going to replace it with the same crappy brand that failed me. This is a $300 part so I'm stuck with it for now. I'll post results later.

 

I wouldn't take a chance on another one. See if you can return that POS and upgrade to an AC Delco or Delphi, most reputable parts stores will work with you. Amazon has them for under $200.

 

I agree with the Captain here I did the samething changed my fuel pump with a cheezy chinese made pump then the gauge didnt work and now I have the same code and its the pressure sensor in the pump. Ive realized the hard way only use acdelco or delphi parts theres a reason they are the parts it came with and that reason is because they are quality!!! ps rockauto.com sucks

Also I've EVAP control issue the purge valve is easy to replace but it was also dead to a faulty wire at the trans cross member.


may the way of the hero lead to the Triforce

 

Finally, I think I've solved the problem. This all started with code P0463, (I changed the fuel pump mod) Didn't fix the problem. Then code P0446. I replace three different vent solenoids and the fuel cap. Still same codes. I got some good advice from member Captain Hook and this is what I found. There are 4 wires going into the tank pump module, Black is ground, Grey is 12v power to the pump, purple is 5v power to the fuel level indicator, black with white stripe is the return signal from the fuel level indicator. I had a good ground and good volts but the dash indicator showed empty. So I changed the pump mod again and again 3 total. I removed and inspected the dash cluster twice. I was about the replace the computer when I decided to trace the wiring.

At the transmission cross over the tiny black with white stripe wire goes to the center an then up alone the left side of the transmission right in between the forward drive shaft and the shift linkage. Bad Location GM. It's a tight fit less than 1 inch from the drive shaft. The drive shaft wore through the wire loom and the black and white wire. A quick splice with a butt connector and the 6 month $500 odyssey is over. I Hope.

Hopefully this will also cancel the code P0446.

 

Good piece of investigating! You might want to solder the connection though, (instead of crimp connector) with rosin core solder and some heat shrink tubing. The location of the connection is subjected to road gunk, water, salt, etc and will corrode before too long.

At the fuel pump module connector, both the fuel pump and the level sender ground wires are black. They both run from the connector to a ground splice pack behind the rear bumper. The fuel pump ground leaves the splice pack as a black wire and grounds on the top of the frame rail, left rear corner. The level sender ground leaves the splice pack as a black with white trace wire. It travels the length of the vehicle and splices with several other grounds, about 4" from the underhood fuse panel. From the splice it goes to the PCM as a black wire in connector 3, pin #19, (IIRC connector 3 is the blue one, not 100% certain though) and eventually to ground inside the PCM. With all that in mind, when I replace fuel pump modules, I solder both black wires together at the module connector, and run a single 14ga wire to the frame near the fuel tank. Solder on an eyelet and bolt her down. This provides a better path to ground with less resistance and distance, and fewer places for trouble, for the fuel pump and the level sender. This would have fixed your problem before it was a problem Anyway, good job, glad you got her figured out and fixed. Thanks for posting back.