This data is for primarily for the 1st generation Diamond Star Motors
The DSM Knock LED
This LED hack is misnamed. More correctly, it's called the Boost Control
Solenoid Open LED. Basically we want an LED to turn on when the boost
control solenoid opens thus dropping boost pressure to around 7PSI.
If we really want to know knock, you want to go back to the
ECUView page, this shows the count that the ECU uses to
determine how much knock it's seeing.
Hooking up the BCS LED
There is an orange wire connecting to the BCS. Tap this line anywhere from the
solenoid to the ECU. Connect this line to a 1K ohm resistor. The other end
of the resistor should be connected to the anode end (positive end, or
longer wire if not cut and bulk, or usually the smaller wire in the plastic
part) of an LED. Wire the cathode (Negative end, shorter wire if LED leads
weren't cut, or the big metal section in the plastic with the LED die on it)
to any convenient ground location. This will work as long as the BCS is
installed. If the BCS is removed, a different circuit is needed.
Why the BCS is closed, thus not allowing any bleedoff of boost to the WGA?
The ECU controls operation of the BCS. Under certain conditions, it is closed
and thus all boost pressure is fed into the WGA, which will open the wastegate
early, reducing the ability of the the turbo to generate boost.
This helps prevent damage to the engine.
Conditions when it's "on" (i.e., boost control solenoid is CLOSED and not
bleeding any boost):
1) It's turned on when ECU is on and engine is not running.
1a) It's turned off by rapid pulsing when the engine starts and there's no
2) It's turned on when the engine is running has seen a lot of knock for the
past few minutes. It has to be consistant knock with no gaps generally.
2a) This condition is stored and doesn't get cleared until there has been a
few tens of miles of knockless operation.
3) It's turned on and pulsed when you're near redline.
This is not acceptable for detecting knock and thus is pretty useless. However,
ECUView does display knock - because it reads the value the ECU gets from the
knock sensor instead of depending on the operation of the BCS.
Where is the knock sensor?
It's on the back side of the engine block underneath the intake manifold.
On a 1G you can contort your arm and body and reach for it underneath the
intake manifold from the battery side of the car. It's probably easier to
hunt for the cable first, which is mounted on the rear intake manifold
Corrected 9/07/2004 after self-proofreading. Proves that the DSM
community really doesn't care.