Knock Control Unit

Knock Control Testing:

1. Connect the LED test light between terminal #1 (test terminal), which is located on the harness to the ignition distributor, and the positive battery terminal.

CAUTION: Damage will result if terminal #1 is connected directly to the positive battery terminal.


2. Turn the ignition "ON".

^ The LED test light should illuminate indicating that the knock control unit is responding. If the LED does not illuminate, check the circuit to terminal #4 of the knock control unit. If the circuit is OK the control unit may be bad. Refer to CHASSIS ELECTRICAL DIAGRAMS.

3. Start the engine and accelerate to above 3000 RPM briefly.

^ The LED should go out, indicating that the system is operating correctly and there are no faults stored. If the LED does not go out, or it goes out and comes back on, a fault has been recognized.

4. If a fault has been recognized, let the engine continue to idle and keep the LED test light in place.
5. Connect a jumper wire from the test connector #1 to ground for at least 3 seconds. The LED test light should flash in coded intervals.

^ Two flashes per interval indicates a fault with the knock sensor wiring, the knock sensor, or the knock sensor control unit.
^ Three flashes per interval indicates a fault with the vacuum connection to the knock sensor control unit or the vacuum signal circuitry of the control unit itself.

NOTE: If the LED does not flash the knock control unit is defective and should be replaced. The fault memory will be erased if the ignition switch is turned "OFF" during this test.

ERASING FAULT CODES

6. Fault codes will be erased after the ignition is switched "OFF", and the engine restarted.

Self Constructed Led Test Light:

If a LED test light is not available, make your own from items purchased from your local electronics store.