Check engine light?

[Rhyno]

Called onstar and they said it is a powertrain fuel delivery problem, code #P446! Anybody have this code before?

[Rhyno]

Called onstar and they said it is a powertrain fuel delivery problem, code #P446! Anybody have this code before?

[MaLLHPPR]

My check engine light came on about 2 mos ago. Dealer said was my gas cap wasn't on tight. So that inturn didn't allow the correct pressure in the fuel system. Seemed weird to me because I had filled up the tank a few days earlier.. the light didn't come on til I was at a quarter of a tank.....Service rep said gas cap didn't seem loose. They also did pressure check the system and didn't find a problem.

Last week the light came on again. Go figure. I always make sure the cap is tight. So back to the dealer I go.

Good Luck!

Kim-

Lovin' every minute of my H2!
Sunset Orange, Lux pkge, air suspension, sunroof.

[Hummie2]

Evaporative Emission (EVAP) Control System Description
EVAP System Operation
The evaporative emission (EVAP) control 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 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 EVAP purge solenoid ON, allowing engine vacuum to be applied to the EVAP canister. With the EVAP vent solenoid OFF, fresh air is drawn through the vent solenoid and the vent line to the EVAP canister. Fresh air is drawn through the canister, pulling fuel vapors from the carbon. The air/fuel vapor mixture continues through the EVAP purge pipe and EVAP purge solenoid into the intake manifold to be consumed during normal combustion. The control module uses several tests to determine if the EVAP system is leaking.



Canister Vent Restriction Test
If the EVAP vent system is restricted, fuel vapors will not be properly purged from the EVAP canister. The control module tests this by commanding the EVAP purge solenoid ON, commanding the EVAP vent solenoid OFF, and monitoring the FTP( Fuel Tank Pressure ) sensor for an increase in vacuum. If the vacuum increases more than a calibrated value, DTC P0446 will set.

Sounds like you have dirt or mud in the vent to your EVAP canister, located on left frame rail about even with drivers door.

Don

[This message was edited by Hummie2 on 05-14-03 at 06:42 PM.]

I think it's a loose gas cap. I had that happen to me with my 03 yukon. C

First American Properties Inc. 916-858-2383
White 03-H2-LUX

[Hummie2]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> posted 05-14-03 07:54 PM
I think it's a loose gas cap. I had that happen to me with my 03 yukon. C

<HR></BLOCKQUOTE>

Maybe so, but I would have expected a loose gas cap to set DTC P0442 or P0455.

Don

The control module uses several tests to determine if the EVAP system is leaking.

Large Leak Test
This tests for large leaks and blockages in the EVAP system. The control module commands the EVAP vent solenoid ON and commands the EVAP purge solenoid ON, 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 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, 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 for the EVAP system. While previous leak detection methods were performed with the engine running, the EONV diagnostic monitors the EVAP system pressure or vacuum with the key OFF. Because of this, it may be normal for the control module to remain active for up to 40 minutes after the engine is turned OFF. This is important to remember 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 start to drop. The EONV diagnostic relies on this temperature change and it's corresponding pressure change 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 inches). The diagnostic can determine if a small leak is present based on vacuum or pressure readings in the EVAP system. When the system is sealed, a finite amount of pressure or vacuum will be observed. When a 0.51 mm (0.020 inches) leak is present, often little or no pressure or vacuum is observed. If the test reports a failing value, DTC P0442 will set.

Check Gas Cap Message
The PCM sends a class 2 message to the driver information center (DIC) illuminating the Check Gas Cap message when any of the following occur:

A malfunction in the EVAP system and a large leak test fails
A malfunction in the EVAP system and a small leak test fails

[Doug]

I too had a check engine light and yes a loose gas cap will cause this. But in my situation the gas tank valve was cracked, being the valve is molded to the tank they had to replace the entire gas tank. Just my experience. No problems since!

Doug
2003 Metalic Red H2
Adventure Series. w/navigation/Sat Radio/Winch

[MaLLHPPR]

I took the H2 to the dealer Thurs. It's still there. They said they are replacing the "charcoal canister" and "vent purge solenoid". Evidently it wasn't the gas cap like last time. (or they diagnosed the problem wrong the first time) The parts are suppsosed to be in Monday and they said definatly shouldn't drive til fixed.

I'll let you know Monday what happened.

Kim-

Lovin' every minute of my H2!
Sunset Orange, Lux pkge, air suspension, sunroof.