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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Pontiac Technician
Category: Pontiac
Satisfied Customers: 29428
Experience:  GM Grand Master Technician 2007. 14 years experience.
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2000 Pontiac Montana: Dave..engine code..temperature gauge

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This question is for Dave Nova(dt69Nova):
What would cause engine code PO128 and PO440 to appear in a 2000 Pontiac Montana?
Both cooling fans remain on while the 'check engine' light is on and the temperature gauge is not moving.However, when the light is cleared the temperature gauge starts to move and the fans shut off.

GM Tech (Cam) :

Hello, I'm Cam. Please include all the details about your issue so I can accurately advise you. I cannot see your vehicle so please be detailed.

GM Tech (Cam) :

Dave Nova is offline at the moment, can I assist you?

GM Tech (Cam) :

P0440 is the evap system performance

GM Tech (Cam) :

The code 0128 is almost always set because of the thermostat opening too early. The computer sees the engine has not reached a set temp in a set time and assumes there is an issue. The code is actually for the coolant temp sensor, but I have yet to see this code set because of the sensor. Replace the thermostat and see. It is not an expensive part.

Dave Nova is offline at the moment, can I assist you?

5:33 PM

P0440 is the evap system performance

5:34 PM

The code 0128 is almost always set because of the thermostat opening too early. The computer sees the engine has not reached a set temp in a set time and assumes there is an issue. The code is actually for the coolant temp sensor, but I have yet to see this code set because of the sensor. Replace the thermostat and see. It is not an expensive part.

Customer: replied 5 years ago.
How about the po440 code?Which component normally goes bad?
Normally the fuel cap goes bad or it sets from fueling with the engine running.
Customer: replied 5 years ago.

Would you say the purge solenoid or vent solenoid likely to go bad on these vehicles thus causing the 440 code?

 

Not usually. Vent sets a p0446 and p0449, pugs sets other codes as well. P0446 is simply a evap performance code.
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