'03 S-10 4.3 temp sensor trbl won't clear sensor just replcd reads 2600 ohms,w/line to comp opened--no grounds--and 1.9 vdc across leads.,once ckt is closed.It usually clrs ,once the weather warms up--not this time--and I can't renew my plates w/ coolant sensor fail(low temp) indication.--- 65,000 miles on vehicle.
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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.
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
Hello! Located in the block is the Coolant temperature sensor....It has two wires in the connector (Blue or Dark Blue and Black)...It is an inverse variable resistor that is to say that as temperature rises the resistance drops...This device is the culprit...At 20 C should read 2000 ohms and at 120 C 200 ohms...Replace the sensor...Guru...saailer
Have you cleaned the throttle valve and the air bypass idle speed control valve? If not do that. When they get really gummed up from backwash from the combustion process they cause this problem of stall on cold start.
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
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.
for the sake of cheap expense could be worth renewing the engine management coolant temp sensor as could be faulty and not telling computer more fuel needed when cold or if have means of a multimeter being handy then check resistance between pins 1 and 3 and measure resistance readings should be approx at a temperature of 10.c between 3350 to 4400 ohms at 20.c between 2250 to 3000 ohms and at 30.c between 1500 to 2100 ohms.Also check resistance of intake air temp sensor between pins 1 and 2 and should read similar to the figures above at them temps too. Hope this helps.
Check Thermostat operation & Temp sensor for ECU.
CHECK ENGINE CCOLANT TEMP SENSOR IN WATERHOSE, NORMALY A 4 PIN PLUG. ON
SENSOR SELF PIN 1&3 OR C&D AT 0 degrees 5000-6500 ohms,60 degrees 530-675 ohms,90 degrees 200-275 degrees
Could also be the cooling fans - I've heard of fixing it by replacing the fan motor and clearing the code as well. The easy fix seems to be the coolant sensor though - I've seen several online threads where owners cleared this code by changing that sensor.