P0496 Code - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Pontiac When starting new posts, please specify YEAR, MAKE, MODEL, ENGINE type, and whatever modifications you have made.

Reply
 
 
 
Thread Tools Search this Thread
Old 05-24-2015, 08:56 PM   #1
Junior Member
Thread Starter
 
Join Date: May 2015
Posts: 4
Thanks: 0
Thanked 0 Times in 0 Posts
GhostRO is on a distinguished road
Default P0496 Code

Disclaimer: I'm not a car guy. I have a 2004 Grand Prix GTP. I have 105K on the vehicle and I'm original owner. In the past few months, I started getting evap codes. The first time was, I believe the P0440 code and my info center said check gas cap. I changed the sensor/canister (AC Delco) that is located in the LR wheel well and I changed the solenoid sensor (AC Delco) at the engine. This was maybe about a month ago and I did this myself.
CEL just came on again and I now have the P0496 code. According to the Auto Zone scan print out, it appears that the only thing I have not changed is the Evap Pressure Sensor.
So knowledgeable people, where is the pressure sensor located on my GTP?
Should I start with replacing that part first or should I check/do something else first?
GhostRO is offline   Reply With Quote
Old 05-25-2015, 12:20 PM   #2
Junior Member
Thread Starter
 
Join Date: May 2015
Posts: 4
Thanks: 0
Thanked 0 Times in 0 Posts
GhostRO is on a distinguished road
Default

Correction previous code was not 0440 it was 0455
GhostRO is offline   Reply With Quote
Old 05-27-2015, 03:11 PM   #3
Senior Member
True Car Nut
 
Soft Ride's Avatar
 
Join Date: Jan 2012
Location: BC Canada
Posts: 3,579
Thanked 335 Times in 298 Posts
Soft Ride has much to be proud ofSoft Ride has much to be proud ofSoft Ride has much to be proud ofSoft Ride has much to be proud ofSoft Ride has much to be proud ofSoft Ride has much to be proud ofSoft Ride has much to be proud ofSoft Ride has much to be proud of
Default

Welcome to the forums!
When I looked up PO455 this is what I found:
P0455 Pontiac Evaporative Emission Control System Leak Detected Gross Leak OBDII Engine Light Trouble Code | Engine-Codes.com
As this really is a large leak detected, did you replace the gas cap with a new OEM one?
Find any cracked lines that might cause a leak ?
Soft Ride is offline   Reply With Quote
Old 05-29-2015, 12:04 AM   #4
Junior Member
Thread Starter
 
Join Date: May 2015
Posts: 4
Thanks: 0
Thanked 0 Times in 0 Posts
GhostRO is on a distinguished road
Default

I am sorry, I didn't make that clear 0455 was the previous code where I replaced the gas cap, solenoid and canister. The current code is 0496
GhostRO is offline   Reply With Quote
Old 05-29-2015, 04:51 AM   #5
Senior Member
True Car Nut
 
Soft Ride's Avatar
 
Join Date: Jan 2012
Location: BC Canada
Posts: 3,579
Thanked 335 Times in 298 Posts
Soft Ride has much to be proud ofSoft Ride has much to be proud ofSoft Ride has much to be proud ofSoft Ride has much to be proud ofSoft Ride has much to be proud ofSoft Ride has much to be proud ofSoft Ride has much to be proud ofSoft Ride has much to be proud of
Default

This site also mentions purge solenoid & has good P0496 diagnostic information & tests.
P0496 EVAP Flow During A Non-Purge Condition

Anyone else got some help in this P0496 situation?
Soft Ride is offline   Reply With Quote
Old 05-31-2015, 01:18 PM   #6
Senior Member

Certified GM nut
 
Tech II's Avatar
 
Join Date: Feb 2014
Location: Worcester, Ma.
Posts: 2,142
Thanked 778 Times in 608 Posts
Tech II has a reputation beyond reputeTech II has a reputation beyond reputeTech II has a reputation beyond reputeTech II has a reputation beyond reputeTech II has a reputation beyond reputeTech II has a reputation beyond reputeTech II has a reputation beyond reputeTech II has a reputation beyond reputeTech II has a reputation beyond reputeTech II has a reputation beyond reputeTech II has a reputation beyond repute
Default

Soft Ride, he says he replaced the purge solenoid.......from his description of the rear, it sounds like he also replaced his vent solenoid.....

The code, P0496, usually means a vac is present, when there shouldn't be....so either the purge solenoid is not sealing(but he replaced it), or the vent solenoid is not opening when commanded, or there is a possible blockage......

Basically, he has become a parts changer, and I guess he wants us to recommend another part to change......his pressure sensor is located on the top of the gas tank....I believe on this year car, he has access in the trunk to it(remove carpeting and then the cover plate).......so the tank does not have to be dropped.....

Basically, the car goes through a system check.....it will close the vent solenoid in the rear , open the purge solenoid, and look for a corresponding drop in pressure(increase in vacuum)......then it will close the purge solenoid, and watch to see if the pressure changes in a prescribed amount of time......when it wants to purge the system of vapors, it will open both solenoids(this brings in fresh air o revove vapors from the charcoal cannister)......during all these tests, the pressure sensor data is monitored by the PCM, for the appropriate data with each action.....

Of course the only way to know for sure is with a bidirectional scanner, like a Tech II....you run the car at idle, you close the vent and open the purge and look for a drop in pressure.....you then seal the system by closing the purge solenoid and see if the pressure is maintained......then you open the vent and see if the vac in the system drops.......

Now the normal fix is replace the purge solenoid(leaking vac)....but he has replaced that, and assuming that it is good.....another possibility is the harness to the solenoid.....the ground side is "pulsed" by the PCM....however, if there is a a rub though condition or a wire that is exposed due to a rodent eating the insulation, then that solenoid could be on, without being "commanded", and could set the code....so check the condition of the harness to the purge solenoid......

If you have a vac gage, you can check the purge solenoid(I know it is new)........disconnect the harness from the solenoid......disconnect the lines from the solenoid(2)....attach the vac gage to the line from the intake....should read around 18".....reattach that line .........now attach your vac gage to that open end of the solenoid......should read no vac at all......now rev the engine several times to 2000 rpms and look at the reading.....should still be zero......if you get a reading, the solenoid is not sealing and is no good....

The other possibility is a PCM problem, but that would be very rare....
Tech II is offline   Reply With Quote
The Following User Says Thank You to Tech II For This Useful Post:
Soft Ride (05-31-2015)
Old 05-31-2015, 01:41 PM   #7
Junior Member
Thread Starter
 
Join Date: May 2015
Posts: 4
Thanks: 0
Thanked 0 Times in 0 Posts
GhostRO is on a distinguished road
Default

I will get on checking the things above and see if it helps. I will keep you updated just for fyi. Thanks again for the help, Soft Ride and Tech II, much appreciated.
GhostRO is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Need OBD-II code help Code: B1242 pkmach1 General GM Chat 8 04-21-2011 10:52 AM
TCC (torque coinverter clutch)code and Evap code at same time?? (fixed) lobi Oldsmobile 16 02-24-2011 11:46 AM
Code P0496 on 2006 lacrosse 3.8L azbuick Buick 12 12-18-2010 05:13 PM
1991 SSE - code 28 code 39 code 42 - losing sleep labonnita 1987-1991 9 12-26-2009 10:58 PM
SSEi Bonnie is having a Nervous Breakdown. Code after Code wug 2000-2005 18 08-24-2008 09:48 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 08:47 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.