Code 25 - Knock Detection System
1) With ignition off, disconnect harness from knock sensor. See Fig 1 . Loosen sensor and tighten to 12-18 ft. lbs. (16-24 N.m) using a 1 1/8" deep socket. Disconnect MCU connector.
2) Connect ohmmeter between MCU connector pin No. 13 and ground. If resistance is less than 1 k/ohm, repair short circuit to ground, and retest. If resistance is more than 1 k/ohm, go to next step.
3) Check continuity between MCU connector pin No. 13 and knock sensor connector (Yellow/Red wire). If less than 5 ohms, go to next step. If more than 5 ohms, repair circuit, and retest.
4) Check continuity between MCU connector pin No. 14 and knock sensor connector (Black/Light Green wire). If less than 5 ohms, go to next step. If more than 5 ohms, repair circuit, and retest.
5) Reconnect Self-Test Trigger jumper on self-test connector. Connect a test light to battery positive terminal. Disconnect knock sensor. Perform steps 1) and 2) of ENGINE RUNNING TEST.
6) Instead of tapping manifold with rod, tap test light to Yellow/Red wire contact in knock sensor connector for 5 seconds. Observe voltmeter. If Code 25 appears, replace MCU. If any other code appears, replace knock sensor.