[Supras] Factory shielding of knock sensors

[Hacker J]

Bernie,

The knock sensors shielding should be grounded from the ECU end only to avoid ground loops. The actual ground used by the factory is the main ECU ground (so-called B ground in the wiring diagrams) which ultimately connects to the bunch of ground wires that get bolted to the intake runners. I would not deviate from this arrangement.

Jon
90T

----- Original Message ----

The '91-up manual set I have here shows the knock sensor cabling to be 
shielded in much the same manner as mods which have been posted on this 
same group.  I inspected the forward most sensor wire and found it to be 
shielded about 2" back from where the overall protective tubing starts 
at the sensor.  According the the wiring schematic, the shields are 
grounded to a common point near the AFM ground.  However, I have seen 
mods involving shield grounding at both the block and the ECU case (with 
soldering to the ECU case whch can be done to aluminum with SAL-Met flux 
with difficulty).  So the factory shield grounding point does not seem 
that outrageous.  Yet I had instances with my '90 where knock sensor 
codes were set.  I have a brand new '90 harness in the original plastic 
bag (which will be for sale) which shows the same shielding.  Maybe it 
was an upgrade from the original. since I did have knock codes set a 
couple of times on the '90 before the BHG.  There were no codes set on 
the '90 when it was received from the dealer. 

Were the list modification comments intended for older harnesses only?  
Both the 91 and '90 manuals show the shielding (referred to as 
sealing").  Any comments would be appreciated.  Thanks.

       BernieK








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