95 Volvo 850 T-5 Killed Another ECT 9186486

[abscate]

Well yes there is a way the car can kill ECT sensors. The ECM applies a current to the sensor and the voltage drop (and current amount) caused by resistance change is how ECM interprets the temp. Mot 4.3 and Mot 4.4 have two level ECT interpretation. Lower current up to about 50C and then higher current above that temp. At low applied current a 1 C difference in temp at 100C range is miniscule and decisions for cooling fan control and some other things is not as accurate. If you increase applied current then the incremental changes per degree are much greater. The problem is the higher current is tough on the sensor. If there is a bad ground or a faulty ECM or a low quality sensor then the failures are greater and more frequent.

The later Bosch systems use periodic higher current pulse to read temp with better accuracy. Denso systems don't seem to have any special tricks but still can interpret temp accurately. Maybe electronics improved in some way????

I think NTCs often roll off at higher temps so then the measurement of higher coolant temp gets more difficult

Has anyone slapped a scope on the sensor to see what kind of waveform comes from the ECU on this puppy?

[TheCynicalCanuck]

So, from what I've heard from you guys and read elsewhere the current plan is to order a new Genuine ECT and put that in once I have my new battery. I just ordered the ECT along with my Control arms and what not so free shipping. And I wouldn't be able to use the old ECT as it was corroded and the wires were fraying.

[abscate]

Sounds like a good plan.

[cn90]

ECT is made by SWF (rmeuropean has it for $40). Dealer about $45.
I'd stick to SWF or Dealer ECT.
When it comes to finicky electronic parts, stick to "known quantity".

[misha]

ECT is made by SWF (rmeuropean has it for $40). Dealer about $45.
I'd stick to SWF or Dealer ECT...

Just make sure it's oem Volvo (which is SWF Valeo btw).

[E Showell]

As mentioned earlier, a known mode of ECT failure is coolant seepage down the wires. It causes the wire to get brittle and causes a solidified, flaky coolant residue at the electrical connector. You may get lucky just cleaning off the wires/connector.

[abscate]

Well yes there is a way the car can kill ECT sensors. The ECM applies a current to the sensor and the voltage drop (and current amount) caused by resistance change is how ECM interprets the temp. Mot 4.3 and Mot 4.4 have two level ECT interpretation. Lower current up to about 50C and then higher current above that temp. At low applied current a 1 C difference in temp at 100C range is miniscule and decisions for cooling fan control and some other things is not as accurate. If you increase applied current then the incremental changes per degree are much greater. The problem is the higher current is tough on the sensor. If there is a bad ground or a faulty ECM or a low quality sensor then the failures are greater and more frequent.

The later Bosch systems use periodic higher current pulse to read temp with better accuracy. Denso systems don't seem to have any special tricks but still can interpret temp accurately. Maybe electronics improved in some way????

I think NTCs often roll off at higher temps so then the measurement of higher coolant temp gets more difficult

Has anyone slapped a scope on the sensor to see what kind of waveform comes from the ECU on this puppy?

Ha! Another project for Corona sequestration

[Eddystone]

So, when we talk about the ECT, are we talking about the electronically controlled throttle module (I guess not if we are talking about an 850) or are we talking about the temperature sensor located near the thermostat housing?

Seems to me that we can create an awful lot of confusion by tossing around Volvo lingo without simply stating what we are talking about. Many of the people asking this kind of question or SEARCHING for solutions might not be using Volvo jargon when seeking help. When I post things, I usually make a real effort to simply describe what the problem is in English so that the database is useful to people looking for help. This is not to single out the people participating in this thread personally, but you can see the confusion that is present here, and we can see that jargon not as helpful as a bit of plain English might be at some point in the conversation.

I've been around this forum for a while and have worked on all of the components mentioned in this thread, and I am confused by this. There should not be a barrier preventing access to information that requires that you already be fully fluid in Volvo jargon to receive help, particularly when less experience people are searching the forum database. Granted, anyone working on their cars should probably know what a lower control arm or a brake caliper is, and we would all perhaps set that bar at different levels.

[E Showell]

ECT = Engine Coolant Temperature sensor.

[abscate]

That’s why I link to the Volvo glossary in my signature, and now I have to figure out why it’s broken

I have been backfilling threads with part numbers for about 2 years now, because there is no other way to make things searchable

Volvo calls things crazy names , but numbers remain pure and searchable, and also pick up year and VIN number changes