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Old 12-07-2019, 03:47 AM   #6
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 43,512
 

2003 L-Series 3.0L Sedan
Default Re: Dreaded P0480 and P0481 code

Don't bother attempting to test the ac pressure sensor if its a three wire unit. The pressure transducer is always on, measuring pressures and outputs varying voltages from approximately 0.1-4.9vdc. The ecm only needs to 'see' one of two pressures and determines when to disable compressor operation; extremely high pressures exceeding approximately 425 psi or very low pressures below approximately 25 psi (from damage releasing refrigerant). Each extreme in pressures are two voltage signals. The ecm simply disables compressor operation to protect the compressor from destroying itself. The transducer does not directly influence cooling fan operation. Put another way, if your ac is working then the pressure sensor is fine. Disconnecting it will not alter ac operation or cooling fan issues but will remove compressor protection. Normal ac operating pressures never exceed 350 psi. Gauges are the only way to measure operating pressures. Something else is causing this error code to return. Normal ac operation automatically turns on low speed fan(s) then ramps up as air, coolant temps and ac pressures rise. Coolant temps are one of several criteria in determining what speed cooling fans are needed whether ac is used or not but ac use always turns on low speed cooling.

The best way to check coolant sensor operation is with a reader; once with a cold engine to compare coolant temps with ambient air temps and at operating temps where its expected to display between 185F-200F before the cooling fans turn on. If you observe cold engine temps matching (within a few degrees of) ambient temps and operating temps within specs, the coolant sensor is fine. What may throw off operating temps would be both fans running that will cool off the radiator.

One or two threads in the Vue forums have reprinted info on when cooling fans turn on. https://www.autocodes.com/p0480_saturn.html is one site describing the error code and what to check. Service manuals - GM, alldata.diy or Mitchell are great sources of info. If I'm not mistaken, the fan control module (next to the battery) is the electrical and electronic interface between both fans and ecm.

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