Please help! 2001 LS with P0446 that won't go away
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Joined: Jan 2015
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Please help! 2001 LS with P0446 that won't go away
P0446 - Evap Vent valve circuit.
I replaced the vent valve and purge valve, neither fixed any problems. I checked the vapor canister for any restrictions...no problems there either. I borrowed a Snap-On scanner from a friend and was able to turn on the vent valve & purge valve. I ended up having to bring it to a shop and they said the PCM was the culprit. They reset and updated it, and the code still came back. They said that the PCM is for sure the problem. I have a few buddies that have been mechanics for over 20 years, they checked it out and said that was definitely not the problem. any ideas??
I need to pass the emission test by the end of next month
I replaced the vent valve and purge valve, neither fixed any problems. I checked the vapor canister for any restrictions...no problems there either. I borrowed a Snap-On scanner from a friend and was able to turn on the vent valve & purge valve. I ended up having to bring it to a shop and they said the PCM was the culprit. They reset and updated it, and the code still came back. They said that the PCM is for sure the problem. I have a few buddies that have been mechanics for over 20 years, they checked it out and said that was definitely not the problem. any ideas??
I need to pass the emission test by the end of next month
Monte Of The Month -- January 2016
Joined: Feb 2013
Posts: 2,293
From: Pacific NW
John, first I would be having a few words with the mechanic that replaced the PCM and never go back. He's way off target.
I would be checking for a pinched, blocked or leaking EVAP hose. Or faulty tank pressure sensor. Do you top off your tank when you fuel up? This can cause charcoal in the EVAP canister to spill out and block hoses. Do you smell fuel at all? The EVAP canister could also still be bad, but I believe the purge valve is sticking open because there is a blockage in one of the hoses and pressure is not reaching the specified value.
You can use a Tech 2 or the Snap-on to do further diagnostics. Some of these diagnostics require a vacuum pump w/gauge to measure pressures through a process of disconnecting hoses and using the scan tool to command purge and vent valves open and closed and reading pressure values to narrow down the point of blockage.
Or with help from an assistant, you can disconnect and blow through hoses to verify they are clear at the other end.
Here's a couple links that might help.
http://coloradofans.com/forums/67-te...ing-parts.html
Hope this helps, keep us posted.
I would be checking for a pinched, blocked or leaking EVAP hose. Or faulty tank pressure sensor. Do you top off your tank when you fuel up? This can cause charcoal in the EVAP canister to spill out and block hoses. Do you smell fuel at all? The EVAP canister could also still be bad, but I believe the purge valve is sticking open because there is a blockage in one of the hoses and pressure is not reaching the specified value.
You can use a Tech 2 or the Snap-on to do further diagnostics. Some of these diagnostics require a vacuum pump w/gauge to measure pressures through a process of disconnecting hoses and using the scan tool to command purge and vent valves open and closed and reading pressure values to narrow down the point of blockage.
Or with help from an assistant, you can disconnect and blow through hoses to verify they are clear at the other end.
Here's a couple links that might help.
http://coloradofans.com/forums/67-te...ing-parts.html
Hope this helps, keep us posted.
Last edited by plumbob; Jul 19, 2015 at 12:11 PM.
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