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Dan, ASE Certified Technician
Category: Pontiac
Satisfied Customers: 2270
Experience:  20 + years working on cars 9 years GM Tech
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Pontiac Sunfire: 2001 pontiac sunfire. 2.2 engine. no trouble

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2001 pontiac sunfire. 2.2 engine. no trouble codes, only has an issue with the fan control as stated here. within the last week, fan only comes on 12 minutes and 30 seconds into runtime as referenced through a scanner from the pcm. the cooling fan can be triggered on and off flawlessly via the scanner through the manual actuation menu. once on, the fan never shuts off or has a command to shut off until the key is turned off even if the engine is externally cooled to 140 degrees coolant temp by spraying with a garden hose. if restarted immediately, the fan will be off until 12.5 minutes of run time and will let the actual engine temp rise dangerously. essentially, the computer is ignoring the coolant temp which is correct and accurate and turning the fan on only 12.5 minutes into runtime. i cannot find the significance of this timed turning on anywhere.
AT what temperature does the fan come on?
I have noticed that on all these J-body cars that once the fan cycles on in the shop in park, it doesn't turn off. All these cars do that. The fans normally will come on at around 227 deg F. I have noticed a lot of the temp gagues reading a little high on these cars.
I just went and looked it up. The Fan comes on at 223deg and it will stay on until the key is turned off or the speed is greater than 5mph for 20 seconds. That is what GM says it does.
Dan and 8 other Pontiac Specialists are ready to help you
Customer: replied 4 years ago.

this is what i just verified with this car. upon starting and remaining in park, fan comes on at 223 degrees or 12mins 30sec of run time (whichever comes first) and remains on until vehicle driven over 5 mph for over 10-20 seconds and temp below 210 degrees. Stop while driving for over 30 seconds and fan may come on at any temperature. fan goes off if temp below 210 once speed is back over 5mph for 10 -20 seconds. stop car and put in park, fan comes on at 223 degrees and turns off at 210 degrees. i have never seen such a complex fan operation algorythm in a car nor such a high temp cut in. wow. i inadvertently fixed the actual original overheating problem when doing the basic checks on the car. the reservoir cap (pressure cap) is sticky where it screws in. the customer did not have it screwed down 100 percent and it was purging coolant out the overflow at these high fan turn on temps and running the coolant slightly low. she topped it off before she brought it to me and stated she saw coolant coming out the overflow. i took it off to check the coolant level and tightened it until it hit the physical stop which stopped the early purging. ill take the $18 advice that led me on the right track and a $10 new radiator cap. thank you Dan from one tech to another!- Ryan

Yea, the first one i saw do this back about 10 years ago, i thought there was something wrong with it that the fan never turned back off. Done a bunch of checks and figured it was a calibration issue until i realized every one of these cars done it. Don't know the reason behind it, why the fan would need to run all the time. But I'm just a tech and not an engineer.
Let me know if you need anything else.