Code P0433, check engine light is on?

BABYBLUE52821

MEMBER
2005 CHEVROLET COBALT
2.4L
4 CYL
2WD
AUTOMATIC
1,540,000 MILES

Car started showing code P0171 code had that fixed it was a vacuum leak then is started showing a P0433 code took it to someone that was a shade tree mechanic They said my purge valve was broken in half I don't know how that happened it was a new problem that started right after the vacuum leak was fixed it just changed codes Any way they replaced the purge valve and brought it back and again the same day the check engine light came back on with the same code PO433 got another purge valve cleared code and drove it a few miles and the light came back on same code Changed the gas cap because I thought they gave me the wrong gas cap which I bought back when it was throwing the PO171 code Anyway reset the code again and once again went a few miles and the light came back on same code checked all the hoses no problems The car is running fantastic no issues its starts on a dime but I can't keep the check engine light off What should I check next The car is due for emissions and I was told it won't pass with the check engine light on I am out of money I have had the car for 4 years and never had much trouble with it I take very good care of it the oil is changed regularly along with other maintenance I just barley put a new alternator on it and a new battery and had it tuned up back in September I don't drive much well I had a shop do it The car is fantastic on gas I just don't know what to check next. Please help me I'm so confused. Thank you

Wednesday, March 5th, 2025 AT 5:05 PM

1 Reply

STEVE W.

MECHANIC
14,490 POSTS

Well, code P0433 is related to the purge valve control circuit. From the description of it being broken off I would suspect the wiring connector, or the wiring itself is the problem.
If you have a scan tool that has bidirectional controls the testing is easy. Without one it's a bit harder. However, the basics are to use a test light connected to ground, unplug the connector and use the test light to verify that there are 12 volts on the pink wire with black stripe. Then to test the other wire (dark green with white stripe) without a scan tool you would need to go to pin 15 on the PCM. Plug the purge valve connector back in, then apply a ground to pin 15 and see if the solenoid activates or connect a test light in place of the solenoid to see it visually. If you apply ground and the light or solenoid don't react you know the wiring is the issue which I suspect is the case. You just need to determine where the break is.

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