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Old 02-04-2018, 09:27 PM   #2
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 43,474
 

2003 L-Series 3.0L Sedan
Default Re: 2001 Saturn L300 Temp Gauge Issues + Blower Issues Help?

1-The coolant temperature display is driven by the body control module (BCM). The coolant sensor sends signals to the ecm.

2-Remove and check for corroded fuses; left instrument panel fuse block (driver's side footwell) 20A HVAC, underhood fuse block HVAC Blower Motor 40A.

You may be describing two separate problems. The temperature display gets its information from bcm - the ecm receiving sensor signals sends info to the bcm to drive the display. One way to differentiate between ecm and bcm handling the coolant sensor signals is how the engine runs from cold startup all the way to full operating temperature regardless of what the temperature gauge is showing. A normal cold engine startup always starts out with rich fuel mixtures based on all sensors but mainly from the coolant sensor as it has a large effect on the ecm adjusting for fuel mixtures. On cold startup, idle should be around 1200 rpm, gradually lowering back to normal (650 rpm) after a few minutes of driving (without referring to the temperature gauge). This presumes the thermostat isn't faulty and regulating operating temps to around 195F.

Check for an intermittent coolant sensor connection, corrosion on connections, etc.. No one has ever reported sensor failure. An intermittent sensor connection or faulty sensor may create oddball engine running symptoms since the ecm relies on continuous signals to adjust fuel mixtures. In addition, check the intake air temperature sensor, mounted behind the front grille on the driver's side. Although its main role is to display outside temps on the hvac panel (auto climate control), it may affect hvac operation.

Its difficult to determine if the hvac panel or bcm is faulty. The bcm is sitting on top of the glove box and has many programs to run almost all the electronics not associated with the engine (ecm) control module.

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