Hi all, I'm a newbie to this forum and have a question regarding a SES code that keeps popping up.
I recently replaced the fuel pump on my 2001 Blazer ZR2 and that was when the light issue first began. I'm getting a p446 code which is a charcoal canister malfunction (according to the manual). I took the canister apart, cleaned the filter, replaced the hoses to and from the canister box behind and below the gas tank, I replaced the gas cap and it still comes back. Thing is that when I clear the code sometimes it stays off for 1-200 miles then it comes back on. It always happens when I'm leaving my driveway for some reason (there is a little dip in the driveway where it always happens).
Another peculiar thing is that immediately after I put gas in the tank I smell a slight fuel odor which eventually goes away. The odor was more pronounced before the new fuel pump.
BTW, the fuel pump was not an OEM part but something that I bought from eBay from a trusted parts supplier.
Any insight is much appreciated.
Aloha.

 

im no technical guru with this stuff but on little thing caught my attention, "the fuel pump was not an OEM part but something that I bought from eBay from a trusted parts supplier" I've heard stories about fuel pumps failing stortly after being installing because they weren't OEM. Get the AC Delco pumps, for some reasons blazers are mated to them.

 

Hey! In my experience,the brand of the pump makes no difference whatsoever,I have had good luck with all reputable name brands! Two things I would check: The gas cap itself(common problem) and the filler neck assembly as these units are of very poor quality and are highly conducive to corrosion issues regardless of the climate where the vehicle resides. I bought a rust-free southern unit and this problem had me going crazy for some time! Good luck!

 

Thanks for the input! I suppose that I should get an OEM gas cap just to be sure instead of the new generic that I bought from Napa. As far as the filler neck assembly, when I changed the pump I put in all new hoses and inspected the neck for corrosion and found none. Despite living in a very salty climate this truck has very little rust at all, mainly surface stuff and some minor under carriage spots.

I've also disconnected the hard lines to the charcoal canister and shot them with the air compressor just in case something was stuck in the line.

No luck!

 

When the PCM runs the monitor for the EVAP system, it relys heavily on data from the fuel level sender and the fuel tank pressure sensor. Both of these parts are included with the fuel pump module and if they are not OEM quality, EVAP codes will continue. Just another of many reasons to get an OEM module

P0446 is indicating a problem in the EVAP vent valve circuit. This flow chart will pinpoint the problem: https://blazerforum.com/forum/showthread.php?t=35143

 

Thank you for your reply, Captain! This is something that I had suspected but I couldn't find any information on. I've been chasing my tail since this all began and it has been frustrating to say the least.

I live in Hawaii and we get screwed on price on everything. The reason that I went with an aftermarket fuel pump is that the Napa store here wanted $600 for an OEM!

Thank you again for your keen insight!

Aloha!

 

I'm not saying that this is your problem, but it is entirely possible for a sensor to be within range but out of calibration. If this is the case, it will not set a DTC indicating a faulty sensor. When the EVAP monitor runs, the test results are based on data from the level sensor and fuel tank pressure sensor. If the data is incorrect, the test results will be incorrect. The reason the SES light is inconsistent could very well be due to the monitor requires a certain set driving situations to be followed for the monitor to run and complete. If you perform a "driving cycle", http://www.obdii.com/drivecycle.html it will force all monitors to run and complete their tests. Each step will force a different monitor to run and complete. You don't need to run all of the steps, and you don't need to run them in order, but you do need to do each step exactly as outlined.

If you smell fuel, and there are no visible signs of leakage, chances are good that there's a problem in the EVAP system. If you follow the flow chart, you'll find the problem.

Just an FYI: If your fuel level gauge on the dash jumps around, is inacurate, or totally inoperative, you will continually get EVAP DTC's until the gauge is repaired. A lot of aftermarket fuel pump modules have this problem right out of the box! The cause.... cheap level sensor with an inferior buffer.

 

Wow, you are quite the fount of knowledge! I will perform this test and see if that doesn't make a difference.
What makes me think that the problem is the aftermarket fuel pump and not a fault in the system per se, is that if it were in fact a system problem I think it would have manifested itself sooner, before I installed the new pump. The old pump would whine and make a terrible noise when the truck was running, it was as is it were always priming. However it was like this for a very long while as it slowly degraded. That is why I think a failure in the system would have reared its head earlier as the pump failed.
Secondly, the aftermarket pump requires that the connector plug that joins the pump to the rest of the harness be removed and replaced with one that they provided. The shape of this plug was much different than the original with the connector being flat and long as opposed to square (I could have this backwards). The wires matched up, of course, but I am skeptical about doing things like that.
The fuel gauge itself does not float about or anything and keeps an accurate reading, however my old pump caused the gauge to read inaccurately once it reached 1/4 tank.
Thanks again for your insight!

 

The harness connector was redesigned. The old style square plug did not make good contact with the module pins. As a result, the plug would overheat, melt, and lose contact completely. When upgrading to the new style oval shaped connector, solder the connections using rosin core solder, don't rely on the el cheapo butt connectors that come with it.

 

Will do! You wouldn't happen to know how to disable the SES light on the dash would you? It's a bit annoying to look at.