Check Engine Light Problem

pink1632 · November 16, 2009

Is it possible for the Service Engine Light to go out when nothing is done to correct the problem? On my 02 Silverado 4x4, 5.3L, 73,000 miles, I've had the light come on quite a few times, giving the same code "P0446 Evaporative Emission Control System Vent Control Circuit Malfunction". The first time my mechanic checked it he cleaned the Sensor on top of the engine (front) and the light went out for two days, then it came back on. The second time it came on, code the same P0446 appeared, he found the Fuel Tank Pressure Sensor was failing, so he replaced that, the light went off. Two weeks later the light came back on, same code P0446, so back to the mechanic I went, this time he just put his computer machine on it and ran a test with it. He said the test passed and when he started the engine the light went out, I asked him if he erased the code and he replied he did not. Two days later the light came back on with the same code showing, so I'm wondering if it is possible for the code to erase itself? Or he erased it himself and said he did not!

Any ideas or suggestions would be very appreciated, my Thanks to those who give honest answers.

redvett · November 16, 2009

The evap test is a random test and after 50 ign. cycles if the fault is corrected the light will go off by its self. I am curious to why your mechanic did not clear the current code after working on the vehicle.

Is it possible for the Service Engine Light to go out when nothing is done to correct the problem? On my 02 Silverado 4x4, 5.3L, 73,000 miles, I've had the light come on quite a few times, giving the same code "P0446 Evaporative Emission Control System Vent Control Circuit Malfunction". The first time my mechanic checked it he cleaned the Sensor on top of the engine (front) and the light went out for two days, then it came back on. The second time it came on, code the same P0446 appeared, he found the Fuel Tank Pressure Sensor was failing, so he replaced that, the light went off. Two weeks later the light came back on, same code P0446, so back to the mechanic I went, this time he just put his computer machine on it and ran a test with it. He said the test passed and when he started the engine the light went out, I asked him if he erased the code and he replied he did not. Two days later the light came back on with the same code showing, so I'm wondering if it is possible for the code to erase itself? Or he erased it himself and said he did not!

Any ideas or suggestions would be very appreciated, my Thanks to those who give honest answers.

pink1632 · November 16, 2009

The evap test is a random test and after 50 ign. cycles if the fault is corrected the light will go off by its self. I am curious to why your mechanic did not clear the current code after working on the vehicle.

Thank you for the reply.

I guess it was because after he ran the test and started the engine the light went off so he didn't reset it. I'm just not sure he has done all that he can do to correct the problem. He is one of the best mechanic's in the state of Kansas and I have been trading with him for close to 20 years and I trust him and his work. I was just curious if the light would go off by itself, you've given me the answer to my question. However, with the light still being on I feel as if there still is a problem.

jpk · November 17, 2009

Evap emisions codes can be thrown by a loose gas cap. I was getting that every so often with my Saab until they came out with a TSB to replace the gas cap.

pink1632 · November 17, 2009

Evap emisions codes can be thrown by a loose gas cap. I was getting that every so often with my Saab until they came out with a TSB to replace the gas cap.

Hey thanks a ton for that information, I'll have the mechanic check it in the morning when I take it to him, it could very well be a part, if not all of the problem... Thanks again

minibike132 · November 17, 2009

Evap emisions codes can be thrown by a loose gas cap. I was getting that every so often with my Saab until they came out with a TSB to replace the gas cap.

Hey thanks a ton for that information, I'll have the mechanic check it in the morning when I take it to him, it could very well be a part, if not all of the problem... Thanks again

A gas cap would be a leak, this code is for a restriction. That isn't the problem.

[email protected] · November 17, 2009

P0446 IS THE VENT VALVE LOCATED ABOVE THE FUEL TANK,THEY ARE BAD ABOUT GETTING FULL OF DUST . REPLACE THE VALVE AND CHECK YOUR EVAP CANNISTER FOR DIRT ALSO

jblakeney · November 17, 2009

Evap emisions codes can be thrown by a loose gas cap. I was getting that every so often with my Saab until they came out with a TSB to replace the gas cap.

Hey thanks a ton for that information, I'll have the mechanic check it in the morning when I take it to him, it could very well be a part, if not all of the problem... Thanks again

A gas cap would be a leak, this code is for a restriction. That isn't the problem.

Gross fuel system Leak would be a fuel cap........ P0442 i think

pink1632 · November 17, 2009

P0446 IS THE VENT VALVE LOCATED ABOVE THE FUEL TANK,THEY ARE BAD ABOUT GETTING FULL OF DUST . REPLACE THE VALVE AND CHECK YOUR EVAP CANNISTER FOR DIRT ALSO

The Fuel Tank Pressure Sensor was the 1st part that was replaced, would the "Vent" valve be the same thing? I don't know if they checked the cannister or not, will relay that concern to the mechanic today. Thank you for the information, this problem is getting on my nerves to such a point that I just want to get it fixed regardless of cost. Thank you

Also, thanks for the information on the gas cap too.

pink1632 · November 18, 2009

SOLVED the DTC P0446 (Resticted/Blocked EVAP Vent Path) problem on my '02 Silverado.

The mechanic finally solved the DTC Code P0446 (Restricted/blocked EVAP Vent Path) problem I was having. The canister was first blown out with air, quite a bit of dust exited, and then the vent line was also depleted of dust in the same manner. After doing a series of tests the vehicle developed another Code of P0440 (Large Leak Detected) so that gave us another problem. The mechanic had to pressurize the fuel tank in order to track down the leak which was discovered to be at the Vent Valve Solenoid itself, during the blow out of at the canister and vent line, the debris covering the leak was dislodged thusly creating the second Code P0440. Total time spent with the mechanic was 7.5 hours Thursday, most of which was necessary due to letting the vehicle cool down in order to run another test. Evidently, there have been several issues by other owners concerning the location of the Vent Valve Solenoid location on 1999-2007 Classic/Old Style Models as soon as the new replacement was ordered; we discovered GM had totally redesigned the set-up. The new part for the 1999-2003 is Service Kit P/N 19207762; with Service Kit P/N 19152349 for the 2004-2007 vehicle year. Cost for this new kit is not cheap, in my area it cost $200.00. What this kit actually does is to relocate the vent filter box away from the present location to an area approximately 4’-5’ forward and along the upper right side of the transmission with the use of 5/8” heater hose. Approximately one hour was required to replace the old Vent Valve Solenoid (at it’s original location) with the new designed one, after which another test was made and everything operated as it should have with no DTC Codes produced.

Thanks to everyone for their replies and suggestions. Hopefully, this "fix" will help others who are experiencing this same problem.

Westlotorn · March 29, 2010

Thanks to all those in this Forum, my 02 Tahoe has been giving this code randomly for over a year. I use my scan tool and shut it off, 2 to 4 mos later I get the code again. Always P0446. I think you have saved me a ton of searching and frustration. Thanks.