850 - 94 T5 Engine Knock Sensors

Hi all

Could I get some advise on knock sensors, I had replaced these new from
Volvo 5 years ago as a knock sensor kit, that is new wiring harness and
knock sensors. In the last couple of months I have had to clear the
emission light, fault codes logged for front & rear knock sensors,
sometimes twice a month, signal missing or faulty knock sensor.
I only ever use premium unleaded fuel from BP Ultimate or Shell
Optimax.

I have had this occour if I idle the engine to long on start up .ie
hitching up the trailer.

Short running while warming up, which I try to avoid. The light comes
on after starting engine again.

and finally when low on fuel and fuel light is on.

This all varies within the above mentioned but generally the light is
triggered during one of these outcomes.

Thanks for any advise in advance.

Gary.

 

My guess it the harness modifications have gone bad from corrosion.
When I did my dad's 850, I cut the terminals off the car harness, and
the adapter harness, and soldered the wires together. You're supposed
to cut the terminals off the car harness, put new ones on (from the
kit), then plug the adapter harness into the new terminals, and plug the
oxygen sensors into the adapter. The way I did it eliminates one
possibility of problems.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

It could be that your spark plug wires are shorting and giving you
misfires that trigger the knock sensors. My 94 850 turbo got so bad it
wouldn't run because of misfires. New wires and the knock sensor codes
quit occurring.