Main IndexAuto Repair Home Search Posts SEARCH
POSTS
Who's Online WHO'S
ONLINE
Log in LOG
IN









DTC PO440


  Email This Post



coachk_23
New User

May 15, 2008, 10:53 PM

Post #1 of 3 (15480 views)
Shortcut
post icon DTC PO440 Sign In

1999 PONTIAC GRAND AM SE
3.4 LITER V6 ENGINE
105,000 MILES

SERVICE ENGINE LIGHT CAME ON WHILE DRIVING DOWN THE ROAD. NO NOISES, NO PERFORMANCE ISSUES. HOOKED UP OBD-2 AND FOUND CODE PO440, CLEARED CODE. REPLACED FUEL CAP WITH NEW ONE. CODE HAS RETURNED. NOT SURE HOW TO DIAGNOSE FURTHER. HOW MANY EVAP SENSORS ARE THERE ON THE PONTIAC GRAND AMS AND WHERE ARE THEY LOCATED? THANKS FOR THE HELP.

coachk_23


DanD
Veteran / Moderator
DanD profile image

May 16, 2008, 11:55 AM

Post #2 of 3 (15466 views)
Shortcut
Re: DTC PO440 [In reply to] Sign In

A P0440 Large EVAP leak sets when the PCM does an EVAP integrity test on the system and it fails.
Large leak is a relative term in this case, anything that will allow pressure to escape from a .020” hole, is considered a large leak.
Any time the fuel level in the tank is from ¼ to ¾ full is when the PCM may run a test.
The PCM will turn on the purge solenoid; which will allow engine vacuum to enter the system.
The PCM will also turn on the vent solenoid sealing the vent.
The PCM will now watch the EVAP pressure sensor, which should be showing an increase in negative pressure in the EVAP system.
Once a certain pressure is reached (depending on fuel level); the PCM will turn off the purge solenoid; completely sealing the EVAP system.
Now the PCM will watch the pressure sensor; timing how long it takes for the pressure to leak down.
So if the pressure cannot be reached or if the pressure degrades too quickly; on comes the light and the 440 sets.
Causes could be the purge solenoid, vent solenoid, pressure sensor, vacuum supply to the purge solenoid, wiring, PCM or a leak anywhere in the system, larger then .020” (pin hole).
The purge solenoid is under the hood, the vent solenoid under the car close to the fuel tank and the EVAP pressure sensor is on top of the fuel tank.
The testing is quite simple with the proper equipment; a scan tool to command the solenoids on & off; an EVAP leak test/smoke machine, to apply smoke to the system under low regulated pressure.
The smoke is there as a visual aid, you won’t see gas fumes leaking out of that small of a hole or leak in a line or solenoid.
You asked and I hope you understand; it’s not just having the knowledge of how the system is designed to work but also having the equipment to run the tests.

Dan.
.

Canadian "EH"






coachk_23
New User

May 19, 2008, 4:34 PM

Post #3 of 3 (15447 views)
Shortcut
post icon Re: DTC PO440 [In reply to] Sign In

THANKS FOR THE EXPLANATION. IT HELPS.




Advertising


  Email This Post
 
 






Latest Forum Post

Hello, My fuel pump went bad today and my car stopped in the middle of the roa...


Car started making humming noises, mechanic said one wheel bearing is going bad....


Hey! I recently got my beloved VW Mk3 Golf 1.4L 1996 (N) MOT'd, I was considerin...


Year of vehicle 2004 Make of vehicle Nissan Model of vehicle Sentra Engine ...


I have a 98 Pontiac grand prix GT with a 3.8L in it... the problem I have is my...


Hey I recently got my beloved VW Mk3 Golf 1.4 1996 MOT'd, I was considering scra...


Feed Button






Automotive Forum Categories
AC Auto Repair
Auto Body Repair
Auto Insurance
Automotive Repair
Automotive Wiring
Automotive World
Brake Systems
Car Care Tips
Car Racing
Car Shows and Events
Car Stereo Repair
Car Troubleshooting
Engine and Car Noises
Engine Fault Codes
Engine Troubleshooting
Exhaust System Repair
Gasoline and Motor Oils
General Discussions
Motor Vehicle Inspection
Motorcycle ATV Repairs
Motorcycle Body Repair
Motorcycle Clutch Repair
Motorcycle Engine Repair
Motorcycle Repair
Motorcycle Seat Repair
Remote Control Cars
Steering and Suspension
The Bargin Bin
Traffic Ticket Help
Tricks of the Trade
Truck Repair
Truck Repair Advice
Truck Engine Repair
Truck Suspension Repair
Car Forum - Sitemap


Search for (options) Privacy