Po441

[jem270]

P0441 Evaporative Control System Incorrect Purge Flow

Stock 1997 Grand Prix 3.8 SE

I checked the vacuum lines from the throttle body to the purge solenoid to the solenoid switch to the charcoal canister. They all look OK. I put in a new purge solenoid and cleared the PO441 code and the code returned. Where is the sensor that actually trips the code and lights up the dash light? I have a hand held vacuum pump and a volt meter. Is there any way of determining if the problem is with the solenoid switch or charcoal canister without buying them? Is there a way of testing these parts? Any way of “tricking” or bypassing the sensor short of pulling the bulb? Car is great except for the annoying dash light.

[corning_d3]

A lot of times the charcoal inside the vapor canister breaks up and gets sucked into the system, causing a clog. Try removing all the lines from the car and blow air thru them. Don't blow air into the solenoids, and don't put any more than 1 psi on the EVAP system while it's installed in the car.

[jem270]

Before I remove any vacuum lines I would like to test the system to see what is wrong. The way I understand it, my system has a purge solenoid which controls the vacuum, a vacuum switch which senses the vacuum and a charcoal cannister which stores the vapors. The vacuum comes from the throttle body and goes to the purge solenoid. It opens when it gets a signal from the computer. The computer uses the switch to see if vacuum is present. Both the purge solenoid and the vacuum switch have electrical connections. I would like to know if I could test the voltage going to them to see if they are getting the right signals. I do not know how much voltage they should get or when they should get it. The Haynes manual I have does not go into testing of the system.

[BNaylor]

Your Haynes manual is too generalized and ineffective on these type problems. You need a GM service manual. DTC error codes such as P0441 are listed along with a course of action. It has the testing procedure for the complete evaporative emissions control system. Waiting for the various solenoids to work would be an exercise in futility. When using a Tech II diagnostics machine solenoids are commanded open/closed based on a sequence of events.

The vacuum pressure switch is located at the fuel tank and is part of the fuel pump assembly. There is a line that feeds from the charcoal cannister to the vacuum switch. The fuel tank must be able to properly hold pressure. The gas cap seal and seal on the fuel pump pod to tank must be good. The vacuum pressure switch must be good. So check all of that.

[jem270]

I just want to make sure I understand. These are pictures of my car. Do I also have a switch on the fuel pump or do only have the one on the engine?

Here is my emission sticker showing evap system


Here is my evap canister


Here is my engine view with the switch (top) and purge valve/solenoid (bottom) marked


Here is the purge valve/solenoid


Here is the switch

[BNaylor]

All '97 and up Grand Prixs are supposed to have the pressure switch at the gas tank. That is what the PCM uses to monitor the evaporative emissions system. In the trunk behind the rear passeneger seat is an access cover. Remove carpeting. To remove 7 nuts hold the cover on. Once removed you will see the pressure switch, the electrical connector to the switch, the electrical connector to the fuel pump and three lines - fuel pressure, fuel return and evaporative emissions all on top of the fuel pump assembly.

Basically, the only real way to tell is inspect to see if you have one. Certain '97 models may not have one but from certain 97.5 and up models they do.

Edit Update: From your pics you have the old style system.

[jem270]

Thanks. I'll take a look.

[BNaylor]

Originally Posted by jem270

Thanks. I'll take a look.

From your pics it looks like you have the old style system but it doesn't hurt to check. I have a 97.5 GTP and my fuel pressure sensor is at the fuel pump pod. The production change took effect around mid-1997. 1998 models and up definitely all have the sensor at the gas tank.

[97gpgtcpe]

Sorry to bring this thread back from the dead, but my 97 Grand Prix GT is doing the same thing. Is it likely that the Purge Valve switch could cause this? I replaced the silenoid, with no luck. I also put a new gas cap on it, and all of the lines look good as well.

Thank you all in advance for your advice, inspection is coming soon, and won't pass with the CEL.

[BNaylor]

Originally Posted by 97gpgtcpe

Sorry to bring this thread back from the dead, but my 97 Grand Prix GT is doing the same thing. Is it likely that the Purge Valve switch could cause this? I replaced the silenoid, with no luck. I also put a new gas cap on it, and all of the lines look good as well.

Thank you all in advance for your advice, inspection is coming soon, and won't pass with the CEL.

Check for leaks or test system to see if it holds pressure (leak down test). Evaporative emissions charcoal cannister and the lines to and from the gas tank and filler neck. The o-ring seal at the top of the fuel pump assembly. Evaporative emissions lines at the fuel pump assembly. If system holds pressure then possibly the pressure switch.

Also, to clarify did you replace the purge valve switch/solenoid?

[97gpgtcpe]

Thanks for the reply. I already replaced the solenoid, but now found a switch online that's very reasonable, so I'll do one of those too.

Going to bring it to a guy who chases down stuff like this, sometime next week or the week after, was just curious if it sounded like the switch itself could be bad.