Check engine light .. i have code...help please

[floatncork]

P0446 EVAP Emission Control System Vent Circuit Malf

this was 1 of 2 codes that were on it....but 2 or 2 was the same exact code as the first. Autozone said the replace the gas cap, i did and it the enngine light still stayed on. Anyone know what this code means?

i own a 1997 4dr LS 4x4.

[Turbocpe]

After replacing the gas gap, did you clear the code by clearing the computer's memory?

[ricksza]

A code P0446 means a restricted or blocked EVAP canister vent path caused by:

A malfunctioning EVAP vent solenoid (stuck closed)
A plugged kinked or pinched vent hose
A shorted EVAP vent solenoid driver circuit
A plugged evaporative canister.

Gas cap won't cause it.

After repairs, the PCM self test for the EVAP system could take a week depending upon driving habits to turn out the light. Or you could have the code cleared with a scanner.

[Turbocpe]

My '98 Blazer factory GM manual lists "loose, missing, damaged, incorrect or improperly installed fuel cap" as a possible issue under this code?

Furthermore, it states "the VCM sets this DTC if the vacuum decay rate is greater than a predetermined value". It uses the Fuel Tank Pressure sensor to determine this.

Using that information, how could a faulty (leaking) gas cap not cause this code? It would allow vaccum to escape?

I've already learned that you know what you're talking about, so please don't think this is disrespect. I'm just a bit confused with what the GM shop manual says.

[ricksza]

I'm using GM's own Service Information Program which is updated at least twice a week.

Document ID# 60258
1997 Chevrolet/Geo Blazer - 4WD
DTC P0446 Evaporative Emission (EVAP) Vent System Performance

A code P0440 is normally a loose gas cap.

[Turbocpe]

Is it possible the codes are different between '97 and '98?

The book is from Helm, so it isn't the cheap books.

[ricksza]

Codes are the same across all OBD2 vehicles. Just not all vehicles can display all the same codes.

[blazee]

When I first saw this, I looked up the code and saw a couple different things for it.

P0446- Evap Canister vent blocked
p0446- EVAP Emission Control System Vent Circuit Malf

[ricksza]

They are the same thing, Vent Circuit Malfunction because the vent function is blocked or restricted.

[Turbocpe]

ricksza, I should have known the 97/98 would be the same on the OBDII, especially since that is a federal code.

But my GM shop manual for '98 states in the first paragraph it states that "the VCM sets this DTC if the vacuum decay rate is greater than a predetermined value".

However, under "Conditions for Setting DTC", it states "The VCM fails to detect a drop in the EVAP system vacuum over a calibrated number of seconds with the vent solenoid open"

That seems to me to give two different (opposite) information on this DTC, doesn't it??

[ricksza]

My info says the same thing in the first paragraph under circuit description...... And we're suposed to use this information to repair the problem.
To make matters worse, if the paper manual is incorrect, they will issue a Service Bulletin about the correction. but with SI, it should have been updated automatically.