Hello,

I have a 01 Blazer S-10 4.3L and i'm having problems troubleshooting my evap system. My codes are P0449, and P0440. So far I have replaced the Evap Vent solenoid, and put on a new gas cap.

I removed the Purge solenoid and tested it with 12v and it opens properly and seals good with no voltage. So i put it back on. I also checked the (Eng 1) fuse and it's good.

I tested both plugs for the vent and purge solenoids and they both have about 11.8v in the plugs with the key on. Not sure if that's normal.

If i reset the codes they come back on right away after I start it. I'm not sure what to check next.

 

DTC's must be diagnosed & repaired in the order they are retrieved. If P0449 was the first one, you will find the diagnostic flow chart here: P0449..Replaced evap vent/valve and reset code..comes back - JustAnswer

After the repair is complete, clear all DTC's and perform a General Motors Driving Cycle. The steps do not need to be performed in order, and you don't need to do step 1. But each of the other steps must be performed exactly as written to allow the PCM to run and complete all EVAP system monitors. If they all run and pass, the check engine light will remain off. If the light comes on, retrieve the DTC's and repeat the procedure starting with the proper flow chart.

EDIT: Better hope this fixes it cuz the P0440 flow chart is a nightmare

 

Thanks for those links, thats good info. The p0449 comes up first and then after i drive it a while the p0440 comes up. I have a basic scanner so i can't activate the solenoids with it.
I have not checked the canister, could a plugged canister cause those codes?

 

The P0449 is most likely a fault in the electrical circuit to the vent valve, or the vent valve itself, (either an open or short circuit). The P0440 means that a problem was detected with the EVAP system. Probably whatever is causing the P0449 is what set the P0440.

 

I already replaced the Evap vent valve. I really don't want to take this in to the shop and get charged an arm and a leg.

I could not find a cut wire but the wires are routed in some hard to reach places. I might run some new wires to the evap vent valve solenoid.

After a lot of research i found out it has a pink wire that goes to the ENG 1 fuse and a white wire (ground) that goes to pin 45 on the PCM Connector C2. I just don't want to fry my PCM.

 

The pink wire does in fact go to ECM1 10 amp fuse in the underhood fuse panel. With the solenoid connector disconnected, it should show battery voltage at the harness connector when the ignition is in the RUN and START positions.

The white wire goes to ECM connector C2 pin #2. The PCM grounds this wire to activate the vent solenoid. With the solenoid and the PCM C2 electrical connectors disconnected: Resistance on the white wire must be less than 5 ohms from end to end. The resistance from either end of the white wire to ground must be infinite, (open circuit).

 

Just a quick update.

I think i fixed the P0449 code. I think it was the electrical connector that plugs into the Evap Valve on top of the gas tank. I looked insided the plug and the tabs were bent back so it wasn't making contact with the pins on the evap valve.

I bent the tabs out again with a needle and sprayed it with contact cleaner. So far it's working. 5 warmup cycles and still no engine light.

A couple years ago i had a shop replace the evap vent valve. They must have damaged the plug trying to test it. Sometimes you have to undo what someone else did.

Side Note: Here is a Youtube video that really helped me. It's a long video for a Silverado but it pretty much describes everything you need to know about this code.

 

Nice. If you want it done right, ya gotta do it yourself

If you perform the General Motors Driving Cycle it will force all of the monitors to run and complete their tests. You don't have to do the steps in order, but you must do each step exactly as written. If you don't do the drive cycle properly, it can take anywhere from a day, to several months before all aspects of the EVAP monitor will run and complete their tests. Each step runs different monitors, but certain functions of the EVAP monitor are run in each step. The EVAP system is the most difficult one for diagnosis and running monitors. With some planning, and a little practice, you can complete the drive cycle in 15 or 20 minutes.

EDIT: Excellent video, the guy knows his stuff! Post #6 (above) is a "safe" way to test the circuits so you don't run the risk of toasting the driver in the PCM.