Chevrolet Colorado & GMC Canyon Forum banner
1 - 20 of 21 Posts

·
Registered
Joined
·
59 Posts
Discussion Starter · #1 ·
So my truck is giving the code P0446 which is evap emission control system vent circuit malfunction. I have read a bunch of the posts on here. They all seem to refer to code 0455. But I am just wondering if changing out my canister will fix this problem. No one seems to say if it fixed their problem when they had code 446. Also if this will fix my problem how much hose will I need to do the cheaper fix, and if someone could give me the part number that would be awesome. From the older posts it seems to have changed over time. Thank you guys for reading and letting me know. If it won't fix it is there something else I should look at?
 

·
Premium Member
Joined
·
3,690 Posts
The truck performs an Emission test to determine if there is a block in the venting. It causes a vacuum to be pulled in the system and then checks to insure that the vacuum is released when commanded. If it holds vacuum, P0446 sets. Barring any wiring problems, it is probably a defective canister vent valve or fuel tank pressure sensor.

You can get a canister vent solenoid valve, part number 214-2149, that should work with a new piece of 5/8" hose. I would suggest to get a couple of feet of hose and trim it on installation and route it to prevent kinks. The valve is available from Amazon for less than $15.

The vent valve that was originally recommended as a cheaper alternative for these trucks, (214-2147), has been changed and now has a square connector receptacle. If you get one, it will require an adapter harness to connect properly.

If the vent valve doesn't fix the problem, the cause could be the Fuel Tank Pressure Sensor. The part number is 16238399 and is also available from Amazon. $24. You have a Regular Cab, so that Sensor can be replaced by removing the left rear wheel well liner and jacking up on the body a bit.

Let us know what happens. Open-ended Threads make the "Search" function more difficult to use, as you have noticed..

You can research the parts for cheaper options. I mentioned Amazon, but they are available elsewhere.
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #4 ·
Thanks for the information cart. I will definitely post on which one fixes the problem I will probably start with the canister and try the other valve later. Hopefully I can get to it tomorrow if not then probably next weekend.
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #7 ·
Well it didn't clear my code it came back on while I was driving home. I am going to have my code read again and see if it has changed. I am not sure if I need to clean out the line, I put in a new one with the new switch, but if you think I still should I don't think it will be too difficult to pull it off and blow it out.
 

·
Registered
Joined
·
16 Posts
Well it didn't clear my code it came back on while I was driving home. I am going to have my code read again and see if it has changed. I am not sure if I need to clean out the line, I put in a new one with the new switch, but if you think I still should I don't think it will be too difficult to pull it off and blow it out.

Mine also came back on after changing that thing out. What did you do to fix?
 

·
Registered
Joined
·
7 Posts
Well it didn't clear my code it came back on while I was driving home. I am going to have my code read again and see if it has changed. I am not sure if I need to clean out the line, I put in a new one with the new switch, but if you think I still should I don't think it will be too difficult to pull it off and blow it out.

Mine also came back on after changing that thing out. What did you do to fix?
I’m in the same boat- I have an 06 2.8l canyon and code po446..replaced gas cap (code)...and vent solenoid (code again)...leaning towards paying a garage now bc I can’t diagnose any further and I’ve exhausted all the internet help I can find...
 

·
Premium Member
Joined
·
3,690 Posts
For the P0446 test the ECM opens the purge valve and the vent valve and checks to insure that a vacuum doesn't go above a specific level. The fuel tank pressure sensor tells the ECM what the vacuum is. A high vacuum indicates a blockage somewhere in the system. A leaking fuel cap will not set a P0446 code.

If the vent valve has been positively ruled out, there could be a blockage in one of the tubes or in the canister. Constant "topping off' when refueling can allow raw fuel to penetrate the canister and deteriorate the carbon causing it to break apart.. If the fuel tank pressure sensor is defective it could be sending erroneous info to the ECM.

The fuel tank pressure sensor is mounted on the top of the pump module. It can be accessed, without dropping the tank, on a Std Cab or Ext Cab. I think the tank has to be dropped on a Crew Cab.
 

·
Registered
Joined
·
7 Posts
For the P0446 test the ECM opens the purge valve and the vent valve and checks to insure that a vacuum doesn't go above a specific level. The fuel tank pressure sensor tells the ECM what the vacuum is. A high vacuum indicates a blockage somewhere in the system. A leaking fuel cap will not set a P0446 code.

If the vent valve has been positively ruled out, there could be a blockage in one of the tubes or in the canister. Constant "topping off' when refueling can allow raw fuel to penetrate the canister and deteriorate the carbon causing it to break apart.. If the fuel tank pressure sensor is defective it could be sending erroneous info to the ECM.

The fuel tank pressure sensor is mounted on the top of the pump module. It can be accessed, without dropping the tank, on a Std Cab or Ext Cab. I think the tank has to be dropped on a Crew Cab.


It was the fuel pressure sensor. Replaced by dropping driveshaft.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
16 Posts
For the P0446 test the ECM opens the purge valve and the vent valve and checks to insure that a vacuum doesn't go above a specific level. The fuel tank pressure sensor tells the ECM what the vacuum is. A high vacuum indicates a blockage somewhere in the system. A leaking fuel cap will not set a P0446 code.

If the vent valve has been positively ruled out, there could be a blockage in one of the tubes or in the canister. Constant "topping off' when refueling can allow raw fuel to penetrate the canister and deteriorate the carbon causing it to break apart.. If the fuel tank pressure sensor is defective it could be sending erroneous info to the ECM.

The fuel tank pressure sensor is mounted on the top of the pump module. It can be accessed, without dropping the tank, on a Std Cab or Ext Cab. I think the tank has to be dropped on a Crew Cab.
I have not found a diagram of the emission lines. At the canister, There is the one which goes from the canister to the Vent valve sol, then 2 others.
I assume the large diameter line (1/2 or 5/8?) goes to the gas tank and the smaller (about 1/4") goes to the purge valve on the side of the Engine? I blew into both w/compr air. The small one seemed like I was blowing against a closed line which I think is correct since the Purge valve should be closed. I removed the gas fill cap, installed a funnel to keep the flap open then blew into the larger line, it sounded like the tank was inflating. Now I've read that there is a check valve? Is that in the plastic line or the fuel pump module fittings? Does the line have to be blow out from the tank end to make sure there are no restrictions?
This is 9-17-18; I started addressing this P0446 code in March 2018. Each time I erase the code & make a change, the code doesn’t come back for a long time, so it’s getting drawn out. 1st, the Vent solenoid had over a 100 ohms resistance, so I replaced it and the tube that came with it, eventually P0446 came back. Then I verified that the new vent vlv still only had 21.4 ohms then tested the purge valve. The Purge held vacuum on both the inlet & outlet and had 22.2 ohms and 12v go to it w/the key on. P0446 came back so I installed an AC Delco gas cap, the code came back. So now I’m wondering about a restricted line, before I replace the Fuel Tank Pressure sensor. I’ve read that on my Reg cab, the sensor can be changed w/o dropping the tank or removing the bed, just by removing the inner wheel opening liner? Is this correct? Thanks for your helpful posts. I have 05 Reg Cab I5

What does 700 Nation stand for?
 

·
Registered
Joined
·
1 Posts
Reg. Cab , have to loosen Bed bolts passenger side, take out bed bolts driver side.
Remove Driver side rear plastic inner fender.
Disconnect filler and vent tube.
Lift and block Bed on driver side.
Clean top of tank, water-soap-water- dry and wipe
 

·
Registered
Joined
·
21 Posts
I recorded a video showing how to remove and install a fuel pressure sensor on 2005 GMC Canyon. Here's the link:
It's a GMC Canyon, extended cab. I would also recommend watching the other videos on my channel showing how to install a purge valve solenoid, and also a vent valve solenoid on a charcoal cannister, for the Evaporative emissions system on GMC Canyon.
 

·
Registered
Joined
·
21 Posts
EVAP SYSTEM OPERATION
The system limits fuel vapors from escaping into the atmosphere. Fuel tank vapors are allowed to move from the fuel tank, due to pressure in the tank, through the vapor pipe, into the EVAP canister. Carbon in the canister absorbs and stores the fuel vapors. Excess pressure is vented through the vent line and EVAP vent solenoid valve to the atmosphere. The EVAP canister stores the fuel vapors until the engine is able to use them. At an appropriate time, the control module will command the purge solenoid valve to be powered ON(valve open), allowing engine vacuum to be applied to the EVAP canister. With the vent solenoid valve powered OFF, the vent is actually open, allowing fresh air to be drawn through the vent solenoid valve and the vent line and into the EVAP charcoal canister. The air/fuel vapor mixture continues through the EVAP hose all the way to the EVAP purge solenoid valve and finally into the intake manifold to be consumed during normal combustion.

Large Leak Test
The control module commands the vent solenoid valve to be powered ON(vent closed) and commands the EVAP purge solenoid valve ON(valve open), with the engine running, allowing engine vacuum into the EVAP system. The control module monitors the fuel tank pressure (FTP) sensor voltage to verify that the system is able to reach a predetermined level of vacuum within a set amount of time. The control module then commands the EVAP purge solenoid valve OFF, sealing the system, and monitors the vacuum level for decay. If the control module does not detect that the predetermined vacuum level was achieved (the system could not pull enough vacuum into the gas tank), or the vacuum decay rate is more than a calibrated level on 2 consecutive tests, DTC P0455 will set.

Small Leak Test
The Engine Off Natural Vacuum (EONV) diagnostic is the small-leak detection diagnostic. The EONV diagnostic monitors the system pressure or vacuum with the engine OFF. Because of this, it may be normal for the control module to remain active for up to 40 minutes after the ignition is turned OFF. Remember this when performing a parasitic draw test on vehicles equipped with EONV.

The EONV utilizes the temperature changes in the fuel tank immediately following a drive cycle to use the naturally occurring vacuum or pressure in the fuel tank. When the vehicle is driven, the temperature rises in the tank. After the vehicle is parked, the temperature in the tank continues to rise for a period of time, then starts to drop. The EONV diagnostic relies on this temperature change and the corresponding pressure change in a sealed system, to determine if an EVAP system leak is present.
The EONV diagnostic is designed to detect leaks as small as 0.51 mm (0.020 in). If the test reports a failing value, DTC P0442 will set.

Canister Vent Restriction Test
If the vent system is restricted (restricted airflow), fuel vapors will not be properly purged(withdrawn) from the EVAP canister. The control module tests this by commanding the EVAP purge solenoid valve ON (valve open), and then commanding the EVAP vent solenoid valve OFF(vent open), and monitoring the fuel tank pressure (FTP) sensor for an increase in vacuum. If there is not a free flow of air/fuel vapor from the vent system, the flow restriction causes vacuum to increase in the gasoline tank, as measured by the FTP sensor. If the vacuum is above the calibrated accepted value, the DTC P0446 will set. The Fuel tank pressure sensor, if not working properly, can also cause a P0446 code.

Purge Solenoid Valve Leak Test
If the purge solenoid valve does not seal properly, fuel vapors could enter the engine at an undesired time, causing driveability concerns. The control module tests for this by commanding the EVAP purge solenoid valve OFF(valve closed) and the vent solenoid valve ON(vent closed), sealing the system, and monitors the fuel tank pressure (FTP) for an increase in vacuum, while the engine is running. If the control module detects that the EVAP system vacuum increases above a calibrated value, DTC P0496 will set, indicating that the purge valve is not fully sealing properly.

EVAP Purge Solenoid Valve
It controls the flow of vapors from the EVAP system to the intake manifold. The purge solenoid valve opens when commanded ON by the control module. This normally closed valve is pulse width modulated (PWM) by the control module to precisely control the flow of fuel vapor to the engine. The valve opens, allowing the engine’s intake manifold air pressure vacuum to create vacuum to enter the EVAP system.

EVAP Vent Solenoid Valve
The EVAP vent solenoid valve controls fresh airflow into the EVAP canister. The valve is normally open. The control module commands the valve ON, closing the valve during some EVAP tests, allowing the system to be tested for leaks.

Fuel Tank Pressure Sensor
The fuel tank pressure (FTP) sensor measures the pressure or vacuum in the fuel tank. The control module provides a 5-volt reference and a ground to the FTP sensor. The FTP sensor provides a signal voltage back to the control module that can vary between 0.1-4.9 volts. A high FTP sensor voltage indicates a low fuel tank pressure or vacuum. A low FTP sensor voltage indicates a high fuel tank pressure.
 

·
Registered
2007 Chevy Colorado LS 2.9L Automatic trans RWD
Joined
·
4 Posts
EVAP SYSTEM OPERATION
The system limits fuel vapors from escaping into the atmosphere. Fuel tank vapors are allowed to move from the fuel tank, due to pressure in the tank, through the vapor pipe, into the EVAP canister. Carbon in the canister absorbs and stores the fuel vapors. Excess pressure is vented through the vent line and EVAP vent solenoid valve to the atmosphere. The EVAP canister stores the fuel vapors until the engine is able to use them. At an appropriate time, the control module will command the purge solenoid valve to be powered ON(valve open), allowing engine vacuum to be applied to the EVAP canister. With the vent solenoid valve powered OFF, the vent is actually open, allowing fresh air to be drawn through the vent solenoid valve and the vent line and into the EVAP charcoal canister. The air/fuel vapor mixture continues through the EVAP hose all the way to the EVAP purge solenoid valve and finally into the intake manifold to be consumed during normal combustion.

Large Leak Test
The control module commands the vent solenoid valve to be powered ON(vent closed) and commands the EVAP purge solenoid valve ON(valve open), with the engine running, allowing engine vacuum into the EVAP system. The control module monitors the fuel tank pressure (FTP) sensor voltage to verify that the system is able to reach a predetermined level of vacuum within a set amount of time. The control module then commands the EVAP purge solenoid valve OFF, sealing the system, and monitors the vacuum level for decay. If the control module does not detect that the predetermined vacuum level was achieved (the system could not pull enough vacuum into the gas tank), or the vacuum decay rate is more than a calibrated level on 2 consecutive tests, DTC P0455 will set.

Small Leak Test
The Engine Off Natural Vacuum (EONV) diagnostic is the small-leak detection diagnostic. The EONV diagnostic monitors the system pressure or vacuum with the engine OFF. Because of this, it may be normal for the control module to remain active for up to 40 minutes after the ignition is turned OFF. Remember this when performing a parasitic draw test on vehicles equipped with EONV.

The EONV utilizes the temperature changes in the fuel tank immediately following a drive cycle to use the naturally occurring vacuum or pressure in the fuel tank. When the vehicle is driven, the temperature rises in the tank. After the vehicle is parked, the temperature in the tank continues to rise for a period of time, then starts to drop. The EONV diagnostic relies on this temperature change and the corresponding pressure change in a sealed system, to determine if an EVAP system leak is present.
The EONV diagnostic is designed to detect leaks as small as 0.51 mm (0.020 in). If the test reports a failing value, DTC P0442 will set.

Canister Vent Restriction Test
If the vent system is restricted (restricted airflow), fuel vapors will not be properly purged(withdrawn) from the EVAP canister. The control module tests this by commanding the EVAP purge solenoid valve ON (valve open), and then commanding the EVAP vent solenoid valve OFF(vent open), and monitoring the fuel tank pressure (FTP) sensor for an increase in vacuum. If there is not a free flow of air/fuel vapor from the vent system, the flow restriction causes vacuum to increase in the gasoline tank, as measured by the FTP sensor. If the vacuum is above the calibrated accepted value, the DTC P0446 will set. The Fuel tank pressure sensor, if not working properly, can also cause a P0446 code.

Purge Solenoid Valve Leak Test
If the purge solenoid valve does not seal properly, fuel vapors could enter the engine at an undesired time, causing driveability concerns. The control module tests for this by commanding the EVAP purge solenoid valve OFF(valve closed) and the vent solenoid valve ON(vent closed), sealing the system, and monitors the fuel tank pressure (FTP) for an increase in vacuum, while the engine is running. If the control module detects that the EVAP system vacuum increases above a calibrated value, DTC P0496 will set, indicating that the purge valve is not fully sealing properly.

EVAP Purge Solenoid Valve
It controls the flow of vapors from the EVAP system to the intake manifold. The purge solenoid valve opens when commanded ON by the control module. This normally closed valve is pulse width modulated (PWM) by the control module to precisely control the flow of fuel vapor to the engine. The valve opens, allowing the engine’s intake manifold air pressure vacuum to create vacuum to enter the EVAP system.

EVAP Vent Solenoid Valve
The EVAP vent solenoid valve controls fresh airflow into the EVAP canister. The valve is normally open. The control module commands the valve ON, closing the valve during some EVAP tests, allowing the system to be tested for leaks.

Fuel Tank Pressure Sensor
The fuel tank pressure (FTP) sensor measures the pressure or vacuum in the fuel tank. The control module provides a 5-volt reference and a ground to the FTP sensor. The FTP sensor provides a signal voltage back to the control module that can vary between 0.1-4.9 volts. A high FTP sensor voltage indicates a low fuel tank pressure or vacuum. A low FTP sensor voltage indicates a high fuel tank pressure.
Thank you for this info!

i have been trying to figure out the cause of my P0446 code, and is it possible that there are more complex or multiple complex issues causing this? Or simply, something other than the common causes for this code?

My only EVAP code before this one, was P0449 I think… or whatever the code is for “high purge flow”. I replaced the purge valve with a “standard motors” brand part.
The high purge flow symptoms and the code went away.
However, my EVAP monitor was incomplete after.
I then replaced my fuel pump, as it was weak. Truck ran much much better, yet EVAP monitor staying incomplete.
While replacing pump, I accidentally broke my tanks roll over valve at the filler neck. So I couldn’t pump gas….
I then got tired and decided I’d give myself a break and trust a shop to handle my mistake.
They replaced my fuel tank with a used one, and although I didn’t need another brand new pump, because I put an aftermarket pump in, I asked them to put a new Delphi pump in, since they’d be replacing my tank, why not go full throttle and never need to pull my tank or remove the bed again for awhile?
SO my truck ran worse than ever before after picking it up, and EVAP monitor is still incomplete.
I suspected they did a crap job, so I pulled my tank and pulled the new pump, and found mud everywhere and inside my new Delphi pump. I also found they CUT my filler hose to remove it, leaving a one inch rip that barely stayed sealed by the hose clamp. They didn’t even put things back together well. They told me they tested my EVAP parts etc, and they were all good.
Yet EVAP moniter remained.
I of course redid everything and got that tank sparking clean and put another new (aftermarket) pump in, and a new filler hose, lines were clear at tank (worn out loose o rings though).

i then FINALLY got a code to pop up, being P0446.

This has been over a year.
Whenever I take my gas cap off, the code goes away. I NEVER get leak codes. Only P0446.

The purge pulse has gotten weaker, when I touch the purge line around near the canister. It used to be stronger. Sometimes I never feel it.

Im always able to refuel. No problems there.

I simultaneously get a lean code too, P0171.

What could my cause of a P0446 be?
Should I replace my purge valve again? Did I wreck its connector?

Is my canister (not valve) but actual vapor canister faulty or partially clogged yet letting me refuel?

If the pressure sensor in tank is what senses this issue, is there a problem with the part of the fuel pump where the vapor goes out into the vapor line to the canister? Basically, Is a fuel pump module ever a cause, aside from just the pressure sensor?

Or did we not clean the tank vent well enough, that’s a permanent part of the tank? That part that has the ball valve and vents to the canister as well?

Did the shop mess up my connectors? Or blow crap into my purge line causing a blockage? Or break anything else to cause this? (Very likely)…

Could my EVAP test port (green cap) be broken, causing blockages near the purge valve? (I tried using it once and worry I broke it).

Lastly, could anything between the purge valve and the intake manifold be a cause for P0446?

THANK YOU FOR ANY RESPONSES!
 
1 - 20 of 21 Posts
Top