coolant temp sensor, sender questions

[modelageek]

Which is which i have 2 sensors in my coolant outlet housing the one in the front works the gauge. the one toward the back is for the pcm. what are they called exactly? I was testing them with my mm and this is what i got so far. the pcm one koeo volts 4.77. Engine had been sitting for 45 min after running ohms=9. warmed engine to operating temp ohms 3 the sensor closest to the front(temp gauge) i did not do the volts yet I did check ressitance when it was at operating temp ohm=.19 does anyone know what these readings are suppose to be.thanks in advance

 

[Bob Ayers]

Which is which i have 2 sensors in my coolant outlet housing the one in the front works the gauge. the one toward the back is for the pcm. what are they called exactly? I was testing them with my mm and this is what i got so far. the pcm one koeo volts 4.77. Engine had been sitting for 45 min after running ohms=9. warmed engine to operating temp ohms 3 the sensor closest to the front(temp gauge) i did not do the volts yet I did check ressitance when it was at operating temp ohm=.19 does anyone know what these readings are suppose to be.thanks in advance

.19 ohms sounds like a shorted sensor.

 

[rurouni20xx]

.19 ohms can make the system signal output somewhere around 4 volts, its utilizing a 5 volt system. the pcm sends 5 volts to the sensor and a variable resistor (in this case a heat activated one) resists a certain amount of voltage. the voltage drop is recorded by the pcm and is programmed in steps so it can see what the engine temp is. put your multimeter inline with the sensor output line and ground and see what it reads, if its between 2-4 volts thats a general spec. if its around .5-1 volt or 4.7-5 volts (open) you have a sensor issue. thats how we check motorcycles all the time, and our fault codes indicate low or high spec voltage faults (seperate codes for each.) the general operating voltages are between 2-4 volts normally on most 5 volt sensors.

 

[Bob Ayers]

.19 ohms can make the system signal output somewhere around 4 volts, its utilizing a 5 volt system. the pcm sends 5 volts to the sensor and a variable resistor (in this case a heat activated one) resists a certain amount of voltage. the voltage drop is recorded by the pcm and is programmed in steps so it can see what the engine temp is. put your multimeter inline with the sensor output line and ground and see what it reads, if its between 2-4 volts thats a general spec. if its around .5-1 volt or 4.7-5 volts (open) you have a sensor issue. thats how we check motorcycles all the time, and our fault codes indicate low or high spec voltage faults (seperate codes for each.) the general operating voltages are between 2-4 volts normally on most 5 volt sensors.

Say What????

Have you ever heard of OHMS LAW????

I sensor resistance of .19 OHMS, and the PCM forcing 4V across it would take about 21 AMPS!!!

 

[modelageek]

this morning dead cold(25 degrees outside) the temp gauge sensor=21 ohms( koeo volts for the wire 8.9 V). the pcm sensor 105 ohms (koeo volts for the wire 4.7). I will bring it up to operating temperature and measure it again. thanks for your help . I am just learning this electrical stuff.

 

[modelageek]

this morning dead cold(25 degrees outside) the temp gauge sensor=21 ohms( koeo volts for the wire 8.9 V). the pcm sensor 105 ohms (koeo volts for the wire 4.7). I will bring it up to operating temperature and measure it again. thanks for your help . I am just learning this electrical stuff.

warmed the truck to OT. temp gauge sensor .12 ohms. pcm temp sensor 3.1 ohms. are these numbers within spec. thanks

 

[modelageek]

oops i was reading the mm wrong. the correct readings are temp gauge sender=21,000 ohms(cold), 130 ohms(hot)

engine coolant temp sensor(pcm)=105,000 ohms(cold), 3,100 ohms (hot)

are these within spec

 

[Bryan22]

that sure seems high, but i can't find any specs in my book, i think i have an extra one, if i can find it i'll test it in a cup of water and let you know.

 

[modelageek]

I have made 6 posts on 3 websites trying to get this answered and no one can do it . I am amazed. I thought it would take 5 minutes. I did find this website http://fordfuelinjection.com/?p=28 and according to it. my 3000 ohmswith a warmed engine( tstat is 192) seems correct but the 105,000 ohms at 324-30 degrees F it should be about 65,000 ohms. .thanks for helping.

 

[Bryan22]

well, if it's right when the engine is warmed, that wouldn't be causing you problems like you were talking about in your other thread.

 

[modelageek]

well, if it's right when the engine is warmed, that wouldn't be causing you problems like you were talking about in your other thread.

yeah it is still there a little when it is warmed up.maybe the sensor is slow?. I cleaned the iac yesterday. it seemed a little dirty and the truck runs a little better.

 

[Bryan22]

really dunno man, did you try cleaning the maf? you run a stock air filter or aftermarket? any codes?

 

[kimcrwbr1]

Is there a reason for testing the sensors. if you just want to find the one for the pcm unplug them one at a time while the engine is warm when the guage dont register you know which is which or if you need the one for the guage unplug them one at a time and take it for a spin if it runs crappy thats for the pcm. If you change the pcm sensor disconnect the battery for an hour then drive it at medium speed for a while to set new values.

 

[modelageek]

really dunno man, did you try cleaning the maf? you run a stock air filter or aftermarket? any codes?

no codes, stock clean air filter, new plugs, wires, pcv, fuel filter, cleaned maf, cleaned butterfly valve, cleaned iac, coolant if full, fuel pressure fine. i wonder if the sensor is just off enough to mess it up.

 

[Bryan22]

kinda doubt it, but if you want to try i think they're only like 5-10 bucks at autozone.