Knock Sensor: Testing and Inspection

Knock System Testing:

1. Connect Mazda Signal Monitor (SST #49 H018 9A1) or equivalent aftermarket "Scan" tool to check connector.
2. Ground test connector with a jumper wire.
3. Turn ignition switch "ON."
4. Tap on the right engine hanger (drive belt side) and check that the signal monitor lamp flashes.
5. If not, connect a known good knock sensor to the vehicle harness and ground it.
6. Repeat the tap test. If lamp now flashes, replace knock sensor. If lamp does not flash, check connections and wiring. If no problem is detected, replace knock control unit.

Knock control unit input can be checked at ECU terminal 1R. At idle, voltage should be 3.3 - 5.0V. When knocking occurs, voltage should be 1.3 - 2.6V.