NOTE: Repair any engine knocking sounds before performing test.

Turn ignition off. Remove BACK-UP fuse (7.5-amp) from underhood fuse/relay box for 10 seconds to reset ECM. Warm engine until cooling fan comes on. Run engine at 3000-4000 RPM for 10 seconds. Retrieve codes. If Code 23 does not appear, problem is intermittent. Inspect for poor connections at ECM, knock sensor, and wiring harness connectors.
Test-drive vehicle and retest. If Code 23 exists, turn ignition off. Connect ECM Test Harness (07LAJ-PT3010A ) to ECM harness, leaving ECM disconnected. See Figure . Unplug knock sensor connector. Test for continuity between test terminal D3 and body ground. If continuity exists, repair short in Red/Blue wire between ECM terminal D3 and knock sensor.
If continuity does not exist, test for continuity between test terminal D3 and knock sensor connector Red/Blue wire terminal. If continuity does not exist, repair open in Red/Blue wire between ECM connector terminal D3 and knock sensor.
If continuity exists, reconnect knock sensor. Temporarily substitute known good unit. Warm engine to normal operating temperature. Run engine at 3000-4000 RPM for 10 seconds. Retrieve codes. If Code 23 does not appear, replace original knock sensor. If Code 23 exists, temporarily substitute known good ECM, then retest system.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Code 23 - Knock Sensor (1.8L GS-R)