2002 Saturn SL cooling fan

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Hi, My SL cooling fan doesn't turn on when the A/C is off and the temp
gauge climbs above it normal range. Turning on the A/C turns on the fan
and the gauge drops quickly to its normal range. What would the logical
trouble shooting steps be to find the fault? Joe


Re: 2002 Saturn SL cooling fan


Here is some information from the service manual for your machine that may
help you figure out what's going on:

Engine Coolant Temperature (ECT) Sensor

The ECT sensor is located in a coolant passage in the side of the cylinder
head near the upper radiator hose. The ECT sensor is a two wire thermistor
type sensor that varies resistance according to changes in engine coolant
temperature. The PCM supplies a five volt reference through a resistor to
the sensor, which is connected to ground. When the sensor is cold it has
high resistance, high signal voltage at PCM. As the sensor temperature
increases, its resistance decreases, lower signal voltage at PCM. The PCM
uses the signal voltage to determine engine coolant temperature.

The ECT sensor is used by the PCM for fuel control, calculation of
temperature of air/fuel mixture at the intake valve in conjunction with the
IAT sensor temperature, Coolant Temp telltale illumination, coolant
temperature gage position and cooling fan relay operation. The PCM also uses
the ECT sensor for ignition timing, exhaust gas recirculation (EGR)
operation, evaporative emission (EVAP) purge solenoid control, idle speed
control and oil life monitoring.

COOLING FAN MOTOR CONTROL
The PCM controls the cooling fan motor by grounding the cooling fan relay.
When the relay coil circuit is grounded, the switch side of the relay closes
allowing current to flow to the cooling fan motor.

The PCM operates the cooling fan relay based on the reading from the ECT
sensor. Under normal operating conditions, the cooling fan operates whenever
the ECT is greater than 105.5C (226F) or the A/C relay is commanded ON
below 113 km/h (70 mph). The cooling fan will turn OFF when the temperature
drops below 100C (212F). If the engine is turned OFF and the ECT is above
107C (225F), the cooling fan can run up to 4 minutes or until the ECT
drops below 107C (225F). If a low/high ECT circuit fault (DTC P0117 or
P0118) is set, the PCM will command the cooling fan relay ON to protect the
engine and transaxle until the condition is corrected.

Degrees(F) Sensor Resistance(ohms)
-40       77k-109k
-20       39k-53k
  0         21k-27k
 20       11k-15k
 40      6.6k-8.4k
 60      3.9k-4.5k
 80      2.4k-2.7k
100     1.5k-1.7k
120     0.98k-1.1k
140       650-730
160       430-480
180       302-334
200       215-235
220       159-172
248       104-113
284         63-68


COOLANT TEMP GAUGE
The PCM controls the coolant temperature gage by sending gage position
messages to the BCM over the class 2 link based on ECT sensor readings. The
body control module (BCM) averages the temperature over time allowing the
gage to move slowly and remain in a relatively stable position as
temperature varies. The BCM then sends the averaged information to the I/P
cluster over the link to position the gage.

COOLANT TEMP TELLTALE
The Coolant Temp telltale is used to alert the driver that the engine may be
in an overheated condition. The PCM controls the Coolant Temp telltale by
sending a message to the I/P cluster over the class 2 link. The PCM will
send the message when the ECT sensor reading is above 118C (244F). If this
condition exists, the PCM will set DTC P0217. If a high temp/low voltage
fault exists in the ECT sensor circuit, the signal is considered invalid and
the Coolant Temp telltale will not be illuminated. The malfunction indicator
lamp (MIL) and cooling fan relay will be commanded ON, however.


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Re: 2002 Saturn SL cooling fan


Thank you very much for that information. I replaced the ECT sensor and
changed and flushed the coolant on Sunday and so far the fan is
functioning properly.  Can  I ask what the source was for the
information you posted? I only have the Hanes manual and it has been
less than complete and confusing at times?


Re: 2002 Saturn SL cooling fan


The information came from the Techline CDs produced by eSI, one of  GM's
entities.  There are six CDs in the set and they have the exact same
information on them as you would find in the official Helms paper service
manuals.  Got them on eBay.  They cover 1998 to 2005 GM vehicles.  Great
bargain.

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