Speedtoys

Just tested..if a sensor goes bad..and goes red, it does NOT go green because its good again on the sensor screen.

So..I have no red sensors.

Lizard928

yup, that is how I know I need to look at it on my car....

dprantl

I had this issue in my car because it has the wrong style knock sensors for my model year. '91 should have the gold-plated contact knock sensors but it has the older style instead so the two connector sides have dissimilar metals. When I disconnected the front knock sensor, there was a bunch of gray dust in there. Once I cleaned it out and reconnected, the problem has yet to return in almost 2 years. At first the symptom was that occasionally the ST2 ignition monitoring screen just the red ignition retarded light would come on and ignition was retarded 6 degrees. Sometimes it corrected itself within seconds, other times it would stay that way until the engine was shut off and restarted. After a couple of months, the front knock sensor light started turning red along with the bottom one.

Dan
'91 928GT S/C 475hp/460lb.ft

John Speake

Roger has stocks for the gold plated terminals for the cable form, that I supply him.....

Speedtoys

Found some fraying on the harness side of the plug where 2 wires COULD touch each other.

I have separated them..will test/observe, the repair.

IcemanG17

This makes sense....while the knock sensors most likely are fine..the harness ISN'T....250K plus miles on it....