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 autopart...

Bougicord only.

If you must go with aftermarket...go with Bosch or NGK.

They will not last and perform like Bougicord...but they will last for a while.

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

Then it is wiring problem for ECT from wiring loom side.

It have to be it...it's a classic bad ECT sensor symptom or it's wiring.

Since ECT is oe and brand new...the connector or wiring for it from wiring loom side is bad.

Main fuel injection relay(grey one) on fan shroud?
Not having lambda light with ignition in posII along with all other lights means that ecu have no power.

Fuse no.1 ok?

It's alternator or voltage regulator...but first...use digital multimeter and measure alternator output directly on it. (+)probe on b+ terminal and (-) probe on alternator housing. Healthy charging system should read 13.8-14.2v at idle with headlights,radio and heater blower up to 2nd speed. Driving...

Sips airbags will not work.

'98 have mechanical sips airbags where '99+ have srs system controlled sips airbags.

Bougicord spark plug wires for 10v cars: https://www.google.com/search?q=volvo+850+10v-bougicord+spark+plug+wires&client=ms-android-tcl-rvo2b&prmd=sivn&sxsrf=AJOqlzXnpG8p-6Ke7VV1ft3FXM0XrJZn4w:1676589252149&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiZ0rvWlZv9AhXmmIsKHRSzB34Q_A...

On n/a it goes to flame trap...turbo doesn't have it.
Sorry i don't have a turbo but i think it should go to PTC nipple.

Vida Dice from '99.