ESC diagnostic

[Bruce Plecan]

-----Original Message-----
From: Joe Boucher <BoucherJC at lmtas.lmco.com>
To: diy_efi at esl.eng.ohio-state.edu <diy_efi at esl.eng.ohio-state.edu>
Date: Thursday, September 03, 1998 11:17 AM
Subject: ESC diagnostic


>I don't think my ESC module is working.  I was experiencing knocking, so I
retarded my timing.  Then I thought, that ain't the way this is supposed to
work.  So, I dug in the factory manual, and
>found some diagnostics.

Pausing here for a moment to state the following is for what I assume is a
gm system!?..,:;';.>.
>
>I thought the system worked by grounding a wire from the ESC module through
the knock sensor.

Nope, the sensor is pezaioelectric  doodad, so it developes a
voltage when shaken, not stirred.

  The one in the Suburban was new when I installed the engine.  The
diagnostics said to disconnect
>the knock sensor and hook that wire "momentarily" to a 12 volt source while
watching the timing mark.  Well, I tried both ways, 12 volt and grounding,
and didn't notice any difference in the
>timing.

Should have like a 7v signal to ecm, sensed knock drops it down,
from there.   If ya'all want I have some 555 circuits that you can
use in leiu of a knock sensor to trigger and hole the esc in a knock
mode.  The output on these is 12v.  If you hook a speaker to em them, they
even sound like a pinging car sorta.
>
>There was voltage at the ECS module, so it is powered.
>
>I forgot to hook the knock sensor up and the next day the check engine
light came on.  I rehooked the wire up and started the engine and the light
was out.

Ecm does a 1st engine "on" diagnostic, and then a while driving
down the street test.  "on" test to look for power on pin something,
and then run test adds a couple hundered degrees for an instant
to see if the knock sensor hears it.  Hundred degrees means a
far amount (40ish)..

  I was rushed and didn't use the ALDL
>to look for trouble codes.  I'm assuming the ECM somehow figured out the
wire was disconnected, but how if the module isn't working?
>
>Any suggestions?

Don't invest in the stock market.
Don't try to train flies, their life span is so short they don't get
to use the education very long..
>
>Thanks,
>
>Joe (Looking for fly turds) Boucher
>'70 RS/SS Camaro  '81 TBI Suburban
>
Hey Joe we got some over here.
Cheers
Bruce       Bashful had a beer with dinner last night and spent the
                 rest of the evening sitting on a 1227747, and making
                 his own sounds effects while using  a flight stimulator.
                 Poor boy can't hold a brew,  but he does have fun....