My 2000 chevy venture i have two engine codes p0449 exhaust gas recirculting sensor circuit low and p0449 evaporative emission control system,vent control circuit malfunction does any body know what would be causing this problem . i replaced my egr vale already and may no difference can some one help

Check engine light code P0449. check engine light ison,autozone says code is P0449 this is whattheir ticket says: The PCM has determined that a malfunction exists in the electrical circuit for the vent valve/solenoid in the evaporative emission control system.
https://chevroletforum.com/forum/impala-14/engine-code-p0449-chevy-impala-59857/

https://www.youtube.com/watch?v=PmK3G-OZobY

DTC P0449 Evaporative Emission (EVAP) Vent Solenoid Control Circuit.
Circuit Description
An ignition voltage is supplied to the evaporative emission (EVAP) canister vent solenoid valve. The control module grounds the EVAP canister vent solenoid valve control circuit to close the valve by means of an internal switch called a driver. The scan tool displays the commanded state of the EVAP canister vent solenoid valve as ON or OFF. The control module monitors the status of the driver. If the control module detects an incorrect voltage for the commanded state of the driver, this DTC sets.

Do you know how to test automotive electrical circuits using a volt meter ? How to test a transistor (driver) inside the PCM . Videos on youtube. Do you know what a wiring diagram is ?
Also search P0449 on youtube . Free wiring diagrams here http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model and engine size . Under system click engine ,then under subsystem click fuel controls . Click search the blue link. Scroll down to #9 diagram . Circuit for vent solenoid . This video is a chevy truck ,doesn't matter .
GMC Chevy Truck DTC P0449 EVAP Vent Solenoid Control Circuit

DTC P0449: Evaporative Emission (EVAP) Vent Solenoid Control Circuit , your vent solenoid is opened or the wiring circuit is . The vent solenoid is by the charcoal canister at the gas tank .
P0449 Battery voltage is supplied to the EVAP canister vent solenoid valve. The control module grounds the EVAP canister vent solenoid valve control circuit to close the valve by means of an internal switch called a driver. The scan tool displays the commanded state of the EVAP canister vent solenoid valve as ON or OFF. The control module monitors the status of the driver.

check engine light ison,autozone says code is P0449 this is whattheir ticket says:

The PCM has determined that a malfunction exists in the electrical circuit for the vent valve/solenoid in the evaporative emission control system.

Definition:
EVAP (Evaporative Emission System) purge/vent solenoid circuit condition

Explanation:
The solenoids and system wiring are monitored for opens or shorts

Probable Causes
1- Purge or vent solenoids defective
2- Check connevtor and wiring
3- Fuel saturated vapor canister
4- Failed EVAP vent solenoid

P0420 - Catalyst System Low Efficiency
P0410 - Secondary Air Injection (AIR) System
P0305 - Cylinder 5 Misfire Detected
P0449 - Evaporative Emission (EVAP) Vent Solenoid Control Circuit

That is a problem in the evaporative emission control system.
Could be anything causing it
Clogged filter in the charcoal canister
A leak in one of the vacuum lines
The purge valve not working,,,etc.
The best thing is to take it and have it checked out, they might have to do a smoke test to find the problem.
All they do is inject smoke into the system, if there is a leak the smoke will come out of it. All it takes is a pin hole in these emission systems to screw it all up.

P0446 Evaporative Emission System Vent Control Circuit.
The following are descriptions of all Evaporative possible codes:

P0441 Evaporative Emission System Incorrect Purge Flow
P0442 Evaporative Emission System Leak Detected (small leak)
P0443 Evaporative Emission System Purge Control Valve Circuit
P0444 Evaporative Emission System Purge Control Valve Circuit Open
P0445 Evaporative Emission System Purge Control Valve Circuit Shorted
P0446 Evaporative Emission System Vent Control Circuit
P0447 Evaporative Emission System Vent Control Circuit Open
P0448 Evaporative Emission System Vent Control Circuit Shorted
P0449 Evaporative Emission System Vent Valve/Solenoid Circuit
P0450 Evaporative Emission System Pressure Sensor/Switch
P0451 Evaporative Emission System Pressure Sensor/Switch Range/Performance
P0452 Evaporative Emission System Pressure Sensor/Switch Low
P0453 Evaporative Emission System Pressure Sensor/Switch High
P0454 Evaporative Emission System Pressure Sensor/Switch Intermittent
P0455 Evaporative Emission System Leak Detected (large leak)
P0456 Evaporative Emission System Leak Detected (very small leak)
P0457 Evaporative Emission System Leak Detected (fuel cap loose/off)
P0458 Evaporative Emission System Purge Control Valve Circuit Low
P0459 Evaporative Emission System Purge Control Valve Circuit High
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At least the cap isn't loose for the gas tank.

I would clear the code with an OBD-II Scanner 'erase code' button, and see how long it takes for it to come back.

p0443 is evaporative emission control system, purge control curcuit malfunction, p0449 is emission control system, vent control curcuit malfunction. p0449 is often a filler cap problem on fuel tank. try tightening cap

i have code reader says p0449 is evaporative emission control system - vent valve / solenoid circuit

P0135 is a bad 02 sensor
P0442 is a evap problem
P0449 is a vent solenoid

i would check the vent solenoid first its a 4ws fuse under the hood in the fuse box make sure you have power to it you should have power at all times the ground comes from the pcm i think if you fix this everything else will work they are all computer controled