ECT sensor wiring 1995 850 N/A Fenix 5.2

[hausmeister]

I am sure the ECT is the same on all these engines

Regarding o2 sensor I would not worry about Hella, they are also an OEM and usually high quality. No idea if they produce their own or rebrand someone elses, but It should be good quality. I guess you could disconnect the O2 sensor to test, for starting it shouldn't matter much (?)

I do have a wiring doc for '97 that has Fenix in it, I will attach it, maybe it helps.

1997_850_wiring_diagram.pdf

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ECT is 7/16 in the table

Hope you can solve it, I also had bad issues with starting an missing (also dependent on temperature and moisture) with my s70 which also had fenix... did not help me much as it never set any codes. in the end my issue was a bad distributor cap.

[Kokonradus]

How do you in general find original parts for your cars? How do I know which is the factory part? Are there some webpages with relevant catalogue info about this cars?

Best way to start is propably to have new original sensors, than I can start with wiring.

[Kokonradus]

It is behaving the same with unplugged o2 sensor. Can´t start the car when it´s cold...

Yes, I know, bad distributor cap can cause several issues. Mine was in bad condition too with totally black burned contacts.... At such a high voltage the electricity can jump through air between contacts and burn them... Spark will be there but very poor. I bought a bosch one from SKANDIX...

Thank you, hausmeister, this is it!

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I will check this schema and figure out what is going on under that hood

But I have no idea where actually is that junction point on the schema Maybe there is something bad.

[misha]

Volvo dealership for OE parts if it's not available in oem.
Ect...for example is SWF which is made by Valeo,but you can't buy it from Valeo or under Valeo...you must go with dealership on this.

O2 sensors are made by Bosch...we use original part number and buy it directly from Bosch or find autoparts store which is able to get them for us.

Aftermarket parts can be used for mechanical stuff,but there are also premium and average aftermarket brands.

Sensors,relays and ignition stuff MUST be oem since these cars will never run properly with aftermarket...if run at all.

[hausmeister]

But I have no idea where actually is that junction point on the schema Maybe there is something bad.

I am not really good with reading these diagrams, but, looking at the other stuff this is connected to it seems to related sensors, and seems to be ground (18). So some kind of shared ground? Not sure if that really is your problem.

Regarding the distributor cap - mine was new but maybe had a defect or fracture... it was not visible until later when I saw the path the electrons were taking, and it was not the right one.

Parts - basically what misha said. Skandix is a good source to find the correct parts and they usually carry ok quality if not original. But can be pricey, always compare.

[Kokonradus]

Ordering new ECT now, I let you know if it will fix the problem.

By the way, I´ve fount catalogue for original volvo parts. http://www.catcar.info/volvo/?lang=en
Bit chaotic, but finally I found what I´ve been looking for!

[misha]

Part number is Volvo 9186486 IF 10v cars use the same like 20v.

[Kokonradus]

Yes Thanks, that´s it.

I have studied this circuits for a while and find out that no continuity on ECT ground wire is definitely a fault! It have no continuity to ECU ground, vehicle ground, the wire is leading nowhere and that can´t be...

The ECU don´t measure the actual resistance between ECT wires! It measures the changes in input voltage like many other sensors in the car (like TPS does by potentiometer). Input voltage 5V is going through yellow wire to sensor thermistor (resistor that changes resistance according to its temperature) and from the thermistor the voltage it´s grounded to ECU ground like in the schema above. When the resistance of thermistor changes, the amount of voltage conducted through sensor to ground changes.

Propably wire or connection is damaged and ECT has due to it too high resistance to ground and ECU thinks I am just stucked somwhere in sweden winter blizzard!

Tomorrow I will take a look on it and let you know. Planning to jump the ECT ground to another sensor ground that is on the schema and has continuity.

[misha]

Ect doesn't send voltage like tps...it sends resistance to ecu like IAT on air box on 10v cars.

Maybe ecu is at fault.

Also...'95 could be different than '96 or '97(later cars).

[Kokonradus]

On the schema IAT, ECT MAP, Cam position and has the same second wire (ground wire). If the ecu measures resistance between two wires of each sensor it would need separate input and separate ground pin for every sensor. On this schema it has one collective ground. The 23/8 is an ground terminal, propably situated somwhere on the engine.

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I will check ground connections on chasis or engine and brush them all. I will try to find it from this scheme

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