ECT Sensor

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

Weird question: Does anyone know anything about the ECT sensor? Has anyone seen any published specs on it, as one might use for testing?

CATCRD · **Posted:** Wed Dec 23, 2020 4:47 pm

It's an NTC thermistor. Here's what I measured on a new one:

Temp/Resistance
73F/2200 ohm
170F/350 ohm

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

That's huge - thank you!!

CATCRD · **Posted:** Wed Dec 23, 2020 5:23 pm

No problem. It actually appears to be the same temp/ohm curve as the fuel temp sensor and TMAP sensor (pins 1-2). I think they're all one of the common types of NTCs.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

That definitely would make some sense! I expected to find at least some values published for testing, but it seems Chrysler prefers the "Doesn't seem right? Replace it" approach. Did you find curves for those other sensors somewhere?

Although not super-precise, this

https://www.ametherm.com/thermistor/ntc-thermistor-beta

suggests the beta is 3530, which is probably ball-park-y enough to get me going.

CATCRD · **Posted:** Wed Dec 23, 2020 6:03 pm

I have a couple of those other sensors laying around and I measured them at various temperatures to come to the conclusion that they had the same curves.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

Ah, cool. Well, I'm glad you did it!

PZKW108 · **Joined:** Sun Apr 06, 2014 5:23 pm **Posts:** 461

thesameguy wrote:

That definitely would make some sense! I expected to find at least some values published for testing, but it seems Chrysler prefers the "Doesn't seem right? Replace it" approach. Did you find curves for those other sensors somewhere?

Although not super-precise, this

https://www.ametherm.com/thermistor/ntc-thermistor-beta

suggests the beta is 3530, which is probably ball-park-y enough to get me going.

The test procedure for the ECT according to the manufacturer is this one:

Bring engine to temp. ( thermostat open) .Turn engine off and wait 10min for temp to stabilized.

Compare the reading from the sensor using DRBIII and a temperature probe on the block near the ECT.

Temp readings should be no more than 13f difference !

This is a water temp sensor it make sense to test it in the coolant, there is nothing wrong with this type of procedure.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

True, but it would be a lot more straightforward to say "read the temp with a probe, measure the resistance of the sensor." For virtually every other car I have owned, there some simple chart that correlates resistance with temp, eliminating the need for a scan tool to complete what should be a quick test.

PZKW108 · **Joined:** Sun Apr 06, 2014 5:23 pm **Posts:** 461

thesameguy wrote:

True, but it would be a lot more straightforward to say "read the temp with a probe, measure the resistance of the sensor." For virtually every other car I have owned, there some simple chart that correlates resistance with temp, eliminating the need for a scan tool to complete what should be a quick test.

You are right about that, the manufacturer is not making it easy for the owner to diagnose his vehicle with minimal tool !

But hey, my home obd2 reader costed me 17$...... A lot less than my multimeter :wink:

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

Haha... you raise a good point. But in this case I need the actual resistance values, not a magic computer converting it to a number. Believe me, I get the irony of having cheap, easy to use tools just give me the answer but actually needing the nuts & bolts information that lies underneath.

PZKW108 · **Joined:** Sun Apr 06, 2014 5:23 pm **Posts:** 461

thesameguy wrote:

Haha... you raise a good point. But in this case I need the actual resistance values, not a magic computer converting it to a number. Believe me, I get the irony of having cheap, easy to use tools just give me the answer but actually needing the nuts & bolts information that lies underneath.

You could always confirm your ECT good with the manufacturer recommended procedure and then unplug The ECT sensor hook your meter to the sensor in place on the thermostat housing so you can read the resistance as well as the housing temp with a temp probe !

layback40 · **Posted:** Thu Dec 24, 2020 6:57 pm

I had the 2 temp sensors fail on my XJ diesel. I opened up the sensors & replaced the thermistors with ones from an electronics store. 50 cents each. Car companies dont make temperature sensors. They just buy standard off the shelf ones from some place. The defineing factor is the thread for fitting. Those who make sensors dont make thermistors, they buy standard ones from an electronic component manufacturer. Google is your friend. The Bosch motor sport site has curves for many sensors like the MAP sensor used on our CRDs.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

Yes, Bosch is very forthcoming with details about their products. Unfortunately, the same cannot be said about Chrysler.

If you know something I don't about the ECT sensor, like who actually makes it or what thermistor it contains, that would be helpful. Taking the one I have apart is what I was hoping to avoid as they rarely go back together as nicely.

WWDiesel · **Posted:** Thu Dec 24, 2020 10:14 pm

These are the part numbers I have on file if it helps any:
Coolant temperature sensor
OEM PN: 5066779AA
Bosch PN: 0281002209

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

That Bosch part number may be key - thank you! Mine has no part number other than the Mopar one.

Edit

Likely this:

https://www.bosch-motorsport.com/conten ... =53698955/

With CATCRD's values I get a beta of 3530, and with Bosch's values I get 3517. Definitely within an acceptable margin of error!

WWDiesel · **Posted:** Fri Dec 25, 2020 2:58 am

Love the chart, it tells all.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

Definitely a good asset to have around!

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

To get deeper into the weeds, does anyone recognize the connector on the ECT as being used elsewhere? I'd really like to find a loose one.

Alternatively, does the ECT wiring run all the way to the ECM, or is there a junction somewhere in the middle that would be convenient to intercept that wiring? I've got my Bosch (TE/Amp) wiring down, but I don't know squat about Chrysler's situation.

WWDiesel · **Posted:** Wed Dec 30, 2020 6:06 pm

Study the wiring diagrams in the FSM, it does show one connector and one splice in the circuit.
According to Mopar Connection Repair list, the connector (05143779AB) is used in a lot of places over several years.
http://connectors.dcctools.com/home.htm
search for kit no. 05143779AB, it will produce a list where it is used, it is quite long. :wink:

ECT Sensor

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