CISIII wiring diagram (Knock Light)

[Marc Swanson]

>     I tried testing my knock sensor in a similar fashion, didn't seem to do
> anything.  Pinging must be a very specific noise that the knock sensor is
> specifically looking for and the hammer doesn't quite do it.

Huw mentioned to me that he had tripped a CISIII knock sensor by using a long
screwdriver and tapping directly on the sensor.  I still suspect a bad knock
sensor.


>     Though I surely know that the knock light was working when I had the
> spark timing all wacky.  When jumping on the gas hard the light came on and
> the power literally shut off in the 80.  Maybe you should give that a shot,
> turn that timing too far advanced and rev the engine, might be enough to
> trip full retard and the light should pop on, watch out for the pinging if
> you really do have a busted knock, but usually if you pull the codes a bad
> knock will show up.

I'm not sure how the engine would check for a bad knock sensor... it isn't
like other sensors that shunt to ground or go open circuit when they are bad.


>     Yes the knock light is the ECS light!  When you hit FULL retard the
> light stays on as long as full retard is being held, or until you restart
> the car.  Mind you this was on my CIS-Motronic 80, but I bet CIS-E III has
> the same function, Bentley says it does.

that's what I suspect... still at least marginally usefull to know that your
engine was knocking fairly hard but it would be nice to get an indication of
any knock.  <sigh>

Thanks for your insight.

-Marc-
87 4ktq
88 90q