Question about Saturn SC2

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The fan in my 2001 Saturn SC2 does not operate. I tested the fan by itself and it works. I measured the resistance of the coolant temperature sensor and it measures good. I measured the resistance of the fan relay coil and it measures good. I need a schematic for a 2001 Saturn SC2.

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  • Saturn Master
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Join the wires on the sensor and see if the fan comes on

Posted on Aug 22, 2010

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I have a 2000 crown vic and my coolant fan wont come on unless i cut the a/c on or unplugged the cylinder head sensor i changed thermostat and temp sensor it still same thing what could be the problem

You have a wiring problem from sensor to the PCM - engine computer .
    Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.
  • Disconnect PCM.
  • Measure resistance between CHT signal and SIG RTN circuits and then between CHT signal and PWR GND circuits at the PCM harness connector.
  • the PCM is what controls the cooling fan !
  • This Pinpoint Test is intended to diagnose the following:
    • Cylinder head temperature (CHT) sensor (6G004)
    • Harness circuits: CHT, VREF, and SIG RTN
    • Powertrain control module (PCM) (12A650)

    Tables and Graphs

    On applications that do not use a ECT sensor, the CHT sensor is used to determine the engine coolant temperature in place of the ECT sensor. In this case the PCM may store both CHT and ECT Diagnostic Trouble Codes (DTCs). To cover the entire temperature range of both the CHT and ECT sensors, the PCM has a dual switching resistor circuit on the CHT input. A graph showing the temperature switching from the COLD END line to the HOT END line with increasing temperature and back with decreasing temperature is included. Note the temperature to voltage overlap zone. Within this zone it is possible to have either a COLD END or HOT END voltage at the same temperature. For example, at 90°C (194 °F) the voltage could read either 0.60 volt or 3.71 volts. Refer to the table for the temperature to voltage expected values.
    Voltage values were calculated for VREF = 5.0 volts. These values can vary 15 percent due to sensor and VREF variations.
    • Run engine at 2000 rpm until engine temperature becomes stabilized.
    • No Starts or Vehicle that Stalls:
      • GO to DL3 .
    • Check that upper radiator hose is hot and pressurized.
    • Rerun Key On Engine Running (KOER) Self-Test.
    Is DTC P1288 or P1116 present? Yes No GO to DL2 . Engine temperature was not stabilized. REPAIR any other DTCs as necessary. DL2 CHECK VREF CIRCUIT VOLTAGE AT TP SENSOR
    • Refer to schematic at the beginning of this pinpoint test.
    • Disconnect throttle position (TP) sensor.
    • Key on, engine off.
    • Measure the voltage between VREF and SIG RTN circuits at the TP sensor harness connector.
    Is voltage between 4.0 volts and 6.0 volts? Yes No There is sufficient VREF voltage. RECONNECT TP sensor. GO to DL3 . GO to C1 . DL3 CHECK RESISTANCE OF CYLINDER HEAD TEMPERATURE SENSOR WITH ENGINE OFF
    • Disconnect CHT sensor.
    • Measure resistance between CHT signal and SIG RTN pins at the CHT sensor. Refer to the table at the beginning of this pinpoint test for resistance specifications.
    Is resistance within specification? Yes No For No Starts or Stalls, RETURN to Section 3 , Symptom Charts.

    All others, GO to DL4 . REPLACE CHT sensor. You need a scan tool to do some of these tests
      Note: Verify that engine is at operating temperature before taking CHT readings.
    • Run engine for two minutes at 2000 rpm.
    • Measure resistance between CHT signal and SIG RTN pins at the CHT sensor. Refer to the table at the beginning of this Pinpoint Test for resistance specifications.
    • Key off.
    Is resistance within specification? Yes No REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ). REPLACE CHT sensor. DL5 DTC P1289 OR P1290: ACCESS CHT PID AND CHECK VOLTAGE
    • Connect scan tool.
    • Key on, engine off.
    • Access CHT V PID.
      Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.
    • Disconnect PCM.
    • Measure resistance of CHT circuit between PCM harness connector pin and CHT sensor harness connector.
    • Measure resistance of SIG RTN circuit between PCM harness connector pin and CHT sensor harness connector.
    Is each resistance less than 5.0 ohms? Yes No REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ). REPAIR open circuits. free wiring diagrams at

Jul 13, 2015 | Cars & Trucks

1 Answer

Radiator fans not working on a 99 dodge Grand Caravan

Hi there:
The engine coolant temperature sensor is a variable resistor with a range of -40 degrees F-265 degrees F (-5 degrees C-129 degrees C).

The engine coolant temperature sensor provides an input voltage to the PCM. As the coolant temperature varies, the sensor resistance changes resulting in a different input voltage to the PCM.

When the engine is cold, the PCM will demand slightly richer air/fuel mixtures and higher idle speeds until normal operating temperatures are reached.

The engine coolant temperature sensor is also utilized for control of the cooling fan.


Fig. 1: Engine coolant temperature sensor location - 3.3L and 3.8L engines

Check this test procedure:

  1. Turn the ignition switch to the OFF position.
  2. Detach the coolant temperature sensor electrical connector.
  3. Using a DVOM set to the ohms scale, connect one lead to terminal A and the other lead to terminal B of the coolant temperature sensor connector.
  1. With the engine at normal operating temperature, approximaterly 200 degrees F (93 degrees C), the ohmmeter should read approximately 700-1000 ohms.
  2. With the engine at room temperature, approximately 70 degrees F (21 degrees C), the ohmmeter should read approximately 7000-13,000 ohms.
  3. If not within specifications, replace the engine coolant temperature sensor.
  4. Test the resistance of the wiring harness between PCM terminal 26 and the sensor wiring harness connector. Also check for continuity between PCM connector terminal 43 and the sensor wiring harness connector. If the resistance measures greater than 1 ohm, repair the wiring harness as necessary.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Jul 18, 2012 | 1999 Dodge Grand Caravan

1 Answer

P0128 code on 2006 ford escape, solutions?

Diagnostic Test Code (DTC) P0128 has a generic description of "Coolant Temperature Below Thermostat Regulating Temperature".

The Poertrain Control Module (PCM) checks the coolant temperature at startup. It then calculates the period of time that it should take for the engine to reach operating temperature (or thermostat regulated temperature). After the calculated period of time, the PCM again checks the coolant temperature. If it has not reached operating temperature, a code P0128 flag is set in mode 6.

If the engine still has not reached operating temperature after 5 more minutes of continuous engine operation, code P0128 is set in continuous memory and the Check Engine (or Malfunction Indicator Light "MIL" is turned on.

Possible causes:

> A stuck-open engine coolant thermostat (MOST common)
> A skewed Engine Coolant Temperature (ECT) or Cylinder Head Temperature(CHT) sensor (working, but not reading correct temperature)
> Low engine coolant level (causing the sensor to not read correctly)

First, the engine coolant (antifreeze) level should be checked. If it is low, it is recommended to perform a cooling system pressure test to find out WHY.

Then, the actual engine temperature should be measured with an infrared thermometer near the ECT or CHT. The reading from the thermometer should be checked against the live sensor data with a scan tool. (PLease note that MOST generic OBD code readers CANNOT perform this function.)

If the reading from the thermometer and the sensor data is within 10 degrees F of each other, replace the thermostat. Otherwise, the sensor circuit should be checked for high resistance (loose or corroded connector, damagd wire, etc.). If no high resistance is measured in the rest of the circuit, the sensor should be replaced.

Jan 03, 2012 | Ford Escape Cars & Trucks

1 Answer

My cadillac deville(2001)runs smooth,but it runs hot.what is the problem?

Insufficient or weak coolant, bad thermostat (out of range), cooling fan not running or kicking into 2nd phase with A/C on, bad temperature sensor, bad temperature sending unit.(false guage reading).
Start by checking your coolant level and color (nice and green or orange? not rusty looking?) if rusty looking, flush coolant system and refill with recommended coolant type of 50/50 mixture.

Check specific gravity of coolant to see if the mixture is weak.

Verify cooling fan is kicking on after engine reaches operating temperature with engine idling.

Replace thermostat.

Measure resistance of temperature sensor. (should slowly raise as engine heats up)

Measure voltage at sending unit. (should slowly raise as engine heats up)

One of those should solve it, I always lean toward weak coolant and bad thermostat. I have seen bad water pumps do that too.


Jun 14, 2011 | 2000 Cadillac DeVille

3 Answers

The cooling fan comes on even when engine is cold and the engine stalls out on my 2001 Saturn l200

Would seem to indicate a faulty coolant sensor. If the sensor is mistakenly triggering the cooling radiator fan to come on then it most likely that it telling the ECU in error that the engine is at running temperature. When the engine is cold at start up the coolant sensor is supposed to inform the ECU of that fact. The ECU then sets a longer injection time to enrich the fuel/air mix to keep the engine running. As the engine warms the ECU responds to the coolant sensor signals by shortening and therefore leaning the fuel air mix. Your engine is stalling due to there not being enough fuel at idle at low temperatures. Check the connections to the sensor, they should be clean and free of corrosion (do not confuse the sensor with the temperature sender connected to the indicator on the dashboard; the sender has only one wire to the top of it). Check that there is continuity between the coolant pins. If it has four pins then the pair of pins diagonally opposed are on the same circuit. If there is a break (infinite resistance) then replace the sensor. You can check the sensor function by removing it and measuring its electrical response when its tip is put in hot water; generally the hotter it is the lower its resistance, with one pair of pins being about half the resistance of the other pair. As it cools the sensor increases its resistance. failure to see this indicates that a new sensor is required

May 09, 2011 | Saturn L-Series Cars & Trucks

1 Answer

My radiator fans are not coming own.

If the fans don't engage after the engine reaches normal operating temperature start the diagnosis by checking the fuse 16 under the dash, and fuse 4 under the hood. If those are good test the coolant temperature sensor by checking the resistance across the two sensor terminals. If the coolant temperature is 50 degrees F then the resistance should be about 5670 ohms the resistance increases at cooler temps and decreases at higher temps. If the sensor is good then have the fan relays tested. Since both fans don't appear to be working the fans are probably ok.

Jan 10, 2011 | 1992 Buick Park Avenue

1 Answer

I recently have a new trany and water pump in stalled and now my temperature gauge does not work. How can I check it myself. Thank u very much for ur time.

Coolant Temperature Sender TESTING a coolant temperature sensor: Using an ohmmeter, measure the resistance between the terminals. Refer to the appropriate chart for your engine. If the resistance is not as specified, replace the sender. Fig. 1: Coolant temperature sender chart — gasoline engines 89552g87.gif
Fig. 2: Coolant temperature sensor chart — deisel engines 89552g89.gif
Fig. 3: Inspecting the coolant temperature sender for resistance 89552g90.gif
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Jul 03, 2010 | 1990 Toyota Camry

1 Answer

Saturn is overheating, tried several things.. nothing is working.

how about the coolant temp sensor, they had alot of problems with that sensor and also the plug for it,some have two of these sensors side by side, one for the gauge and the other for the fan, i would replace these first and go from ther good luck,

Apr 10, 2010 | 1997 Saturn SC

1 Answer

2001 saturn sc2 gets code 341&340 camshaft sensor

if you have high resistance in secondary ign. system (plug wires, ign.coil) this will cause this code to set. make sure you are using a high quality spark plug wire set. not from autozone!!! and denso non platinum tipped spark plugs. also use a diaelectric grease on plug wires to keep moisture out.

Feb 18, 2009 | 2005 Saturn SC2

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