Question about 1999 Saturn SL
Well there are 2 coolant sensors,,,one is the coolant level sensor which is internal to the coolant resivor,,but i think you are talking about the infamous engine coolant temp sensor,,,,ok pop your hood you will see the cam cover that says saturn on it,,,,thats the top of the engine,,,ok,,,then on the lower right side of that you will see the upper radiator hose,,,and the EGR valve,,,,now inbetween the egr valve and upper rad hose is where the coolant temp sensor is,, its just below them,,there is a little wiring harness with a yellow and a black wire going to it,,,,it actually screws into the lower side of the cylinder head,,,,just squeze the wiring connector at the 2 thicker spots and pull it straight off then take the coolant cap off the resivor,,to relases pressure and put it back on,providing the car is not hot,,,,the sensor is actually a 13mm or 14mm socket that removes the sensor,,,,,they usually crack and leak into the harness so check the harness for corrosion,,,,be like green/blue on terminals,,if so youre gonna have to wire in a new connector,,,,no big deal ,, normal s-series issue,,,do not use aftermarket junk like autozone as these do not read correctly from the start youre gonna have to shell out the money at the saturn dealer for the good stuff ,,like $18 for the sensoe and $37 for the connector but it comes with the 2 **** connectors you need to wire it in,,,so if you remove the sensor just put the new one in snug but dont break it off,,,,top off coolant,,,,cut the 2 wires off the old connector as close to the end as possilbe. so you retain as much wire as you can,,,,,it doesnt matter which wire goes on what side but i lke to keep it the way it was the black wire on the right and the yellow on the left,,use the **** connectors,then heat shrink them and wrap them with electrical tape and youre done
Posted on Oct 25, 2009
On the 1999 there is ONLY (1) (CTS) Coolant Temp Sensor!
This sensor sends information to the (PCM) Powertrain Control Module that controls the Coolant Temperature Gauge located in the Instument Cluster and also helps in calculating Fuel Air Mixture so the car won't flood on cold mornings keeping your O2 Sensor from contamination during the open loop start process. It also continues to monitor coolant temp after start up, keeping your emissions low as it sends the temp info to the PCM to help calibrate the Fuel To Air Ratio along with the O2 sensor.
This is a very important part of the emissions system that is continually overlooked when tring to fix Hard Starts and High Emmisions values!
The ORIGANAL CTS where made of a Plastic that always Cracked causing Coolant to leak out of the Dark Brown tip causing corrosion to the 2 wire connector!
You must replace both the connector and the CTS if the CTS is made of plastic.
If not, you will continue to have False CTS values creating Hard Starts, High Emissions and Poor Fuel Economy!
The CTS is located under the drivers side of the motor.
Follow the upper radiator hose, and look for 2 wires together coming out of the cylinder head below the upper radiator hose and to the left of the EGR Valve.
The 1991-1994's SOHC & DOHC heads had 2 CTS Sensors in the same location, 1 has a Gray tip at the end where the connector slides over and ONLY HAS 1 wire (this is for the Coolant Temp Gauge ONLY!) it is located higher then the 2 wired CTS Sensor!
In these years ONLY the 2 wired CTS would Crack!
The single wired CTS gauge sensor never had problems due to the fact it was made of Brass!
Your replacement CTS (2) wired Sensor is also made of Brass, which has kept them from cracking after they where replaced!
One other bit of knowledge, the TTS or Transmission Temp Sensor is the exact same sensor as the CTS and also had the same Cracking issues, causing a Transmission Fluid leak that are misdiagnosed as a leaking Spin on Trans Filter!
The TTS is located above and to the right of the Trans Filter.
If this sensor is found to be leaking, replacing the sensor is all that is required as the connector with the 2 wires will not be damaged!
Hope this information was helpful!
Happy Saturn Motoring! ;-)
Posted on Jul 21, 2014
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Posted on Jan 02, 2017
These are located in the cylinder head in the back of the head...meaning 180 degrees from the belts and pulleys(front) or the side the transmission is on. Two sensors exist...the single wire sensor is for the dash gauge. Saturn pn# 21025106 is the one you need
Posted on Aug 12, 2009
SOURCE: location of ECT sensor
when you open the hood take your right hand and follow the upper rad hose down to the eng. when it stops thats the themostat housing the ect sensor is screwed into that housing there are two sensor one will have one wire and the other will have two you want the two wire one. be carful remove the conector the like to break good luck kdc744
Posted on Jan 08, 2009
The coolant temp sensor is on the driver's side of the engine in the head. If you remove the lid to the airbox and lift the intake tube, you will be able to reach it easily. To remove the connector, you just squeeze it. Then use a socket or a wrench to remove the coolant temp sensor. You will lose some coolant so be ready with the new one or drain the antifreeze before you start.
Posted on Jan 09, 2009
the coolant temp sensor is located on the right side of the cyl head its small under by the upper rad hose 13mm socket removes it after u take the small connector of,make sure the car is cold coolant will come out when u remove it,,,,check the connector too for corrosion,by only saturn sensor the cheap autozone and aftermarket ones dont read right and give you the same problem as the old bad one
Posted on Oct 04, 2009
The ects in located on the drivers side up towards the top and into the side of the block has a small 2 wire plug,make sure when you buy this that you tell them sensor and not switch as they look the same,do this with the engine cool,remove the coolant tank cap to relieve pressure and coolant loss will be very small.
Posted on Dec 25, 2008
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