Purge / Vent Solenoid P0455

Purge Vent Solenoid P0455

How do you test the EVAP system using a bidirectional Scan Tool?


First of all, you can not check the system if you have no idea how the PCM tests the circuit.  If you have a basic knowledge of the system, this will go a long way when you test EVAP System. 


There are a number of ways to test the EVAP circuit with or without a scan tool.  


A good scan tool should be able to perform bi-directional control functions, for example, you can turn a solenoid on and off and confirm its operation.


Here is a good example, let's say a vehicle comes into your shop with a code P0455 gross leak. You probably will start to look at the gas, so let's say the gas cap was already replaced, now what would you do?


Remember on a previous page "Basic EVAP Overview." I had mention the vent valve only closes during testing. During testing the vent valve closes so the system can pull a vacuum. 


But if the vent valve is stuck open when the purge valve is a command on a stuck open vent valve will not be able to pull a vacuum. 


So when the monitor runs a test on the circuit, it will fail, and if it fails twice the MIL will come with a DTC. 


So that is pretty obvious a stuck open or missing component will cause a P0455 code with a MIL on the dashboard. 


But did you know a stuck close purge valve will also cause the same problem, this was a surprise to me? A stuck closed purge solenoid will also prevent the vacuum from building in the EVAP system, and the result will be a gross leak and DTC P0455.


So a large leak will prevent a vacuum from building up, so it's a good idea to confirm the Purge / Vent Solenoid are functional. 


This can be accomplished with a vacuum pump, smoke machine, amp meter or a bi-directional scan tool. 




Basic GM EVAP Overview

If you like the information on  this page PLEASE CLICK The LIKE BUTTON


CLASS SCHEDULES

Emission Control 1:

(Inspector  "Smog" License): 8am - 1:45pm 

8/15/2017 - 9/22/2017

11/03/2016 - 11/28/2017

Class # 799065


Engine Performance 1:

 8am - 1:45pm

10/21/2017

Class # 799069


Engine Performance 2:

(Repair "Smog" License) 8am - 1:45pm

close until Jan 2018

Class # 799071


Emission Control 1

(Inspector "Smog" License):6pm - 8:45pm

M/W nights: 8/16/2017 - 12/13/2017

Class # 799065


Emission Control 2: 

(Repair "Smog" License):

close until Jan. 2018

M/W nights N/A

Class # 799067


Exhaust Emissions (Update Class):

5:30 pm - 8:45 pm 

Tuesday nights: 

8/15/2017 - 9/19/2017

09/26/2017 - 10/31/2017

11/07/2017 - 12/12/2017

Class # 796070