I have the missing problem with my 1992 4Runner and just had a Coolant temp sensor put in. The mechanic said it was reading at 89 ohms and should be 12? Or other way around. Can someone explain what ohm means and could that be the cause of my engine missing? I will be taking it on a big drive tomorrow. Does it take time to send signals with that much of a difference? I am clueless to 89 vs 12? Help
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Re: Coolant Temp sensor
The coolant temperature sensor should read at approx 1,800 ohms between 68 and 88 degrees F. As the temperature lowers, the resistance rises. More ohms. As the temperature rises, the resistance lowers. Less ohms. At 210 degrees, the ohms would be about .15 K ohms.
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Re: Coolant Temp sensor
I agree with gasitjr also if the sensor was bad He could have checked the temp reading on his computer when the truck was cold or hot usualy it will give a fause reading also. The miss could be from a numbe rof thing s plugs wire coil injector or a week clynder
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The difficulty factor of not being there coupled with the absence of a trouble code is high...One possible cause is a defective coolant temperature sensor which is falsely telling the PCM that the temperature is too high...See diagram below location of CTS (coolant temperature sensor) disconnect connector...set ohm meter on X10 scale (you are looking to read 6000 ohms)...place probes on sensor leads not connector...At outdoor temp of 70-80 degrees meter must read about 5400 ohms...If it reads 1100 ohms or less sensor is defective...test two; measure from top of negative battery terminal, with meter set the same, place other lead first on bare metal of fender;READ...Then on bare metal of engine; READ...Both readings must be less than 50 ohms...If meter reads high (1000-2000) ohms you have found the fault...Install braided ground straps from - batt to chassis and block...Let me know the results of these two basic tests...
There are 2 sensors 1 is temp sensor for dash gauge and 1 is engine coolant sensor for computer. Does the upper radiator hose get hot and pressurized. The engine coolant sensor has two wires one has a reference voltage 5 volts and the other is signal return to computer with key on is will have a minimal voltage .25 volts this tells you that the wire is not broken between sensor and computer. the sensor is a negative coefficient sensor average sensor range about 390 ohms warms and 2400 ohms cold engine.
The ECM doesn't read the temps. it only takes the readings from the sensors and tries to adjust within given parameters. You has a coolant sensor on the car you have a temp sensor on the car. Check the wiring, make sure you didn't plug the wrong wire to the wrong sensor. Check to make sure everything is actually plugged in and getting power. It's definitely either bad wiring or a bad temp sensor.
you are trying to test, the readings should equal the temp, lets say like now you have it out it should read the temp of air, if you had it in the car and tested it with cold engine and then test as engine runs and coolant gets hot you would see the readings change, this way is okay if it reads the temp of the air but i would also do it installed with engine running .
There are more readings in between these temps but this should help i will enclose a web site if you need the other readings. this chart is good and readings have a + or - of 50ohms. good day. www.gmtemperaturesensorchart
he coolant thermo sensor is located on the outlet to the upper radiator
hose. It has green connector and facing up. Air thermo sensor is inside
airflow meter housing.
Remove the 2 wire connector lead. If the fans start up immediately, the temp fan switch is faulty.
If you measure the sensor, using a multimeter on ohms, it will read
around 0.5 ohms. Put the sensor into boiling water and measure the
sensor again. It will only have risen to around 2.5 to 3.0 ohms. This
confirms that it is unserviceable.
You may have a coolant or manifold temp sensor that is out of range enough to give you a slight problem but not bad enough to create a code. Check ohm readings: coolant sensor should read about 7,000 ohms cold and less than 1,000 ohms hot. Manifold sensor should read 4,000 ohms or less after it has warmed up and should decrease with any rise in temp. Slight vacuum leaks can give you problems cold as well...check all hoses and fittings for loose fit or cracks. An injector with a slight leak can also flood one cylinder overnight, just enough to give a rough idle till it clears itself out. Damp ignition parts (cap, rotor, wires and coil) can also give the same symptoms and that too may disappear after engine heat drys them up. OK, I've thrown a lot at you but there are quite a number of things that can cause your problem. If the vehicle was in my shop, I'd need to check all of them and possibly more to find it. You need to go over everything carefully. Haynes and chilton list those tests and more and may also be helpful.(available in most larger parts stores) good luck
make sure you cooling fan is coming on (this should when the temp guage starts to climb) and also make sure the temp sensor that turns it on/off is good. You could also have low coolant or bad thermostat (the wrong mix of coolant) or oher major mechanical issues but start with the fan and coolant level/mix