DTC 63: Secondary HO2S (Sensor 2) Circuit Malfunction NOTE: Information marked with an asterisk (*) applies to D15Y4, D17A2 (KU, KQ, KZ, FO models), D17Z1 (KQ model) engines. Reset the ECM/PCM (see page 11-168). Jump the SCS line (see step 2 on page 11-167). Start the engine. Hold the engine at 3,000 rpm (min-1) with no load (in Park or neutral) until the radiator fan comes on, then let it idle for at least 1 minute before test-driving. Is the MIL on and does it indicate DTC 63? YES - Go to step 4. NO - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the secondary HO2S (Sensor 2) and at the ECM/PCM. Inspect fuel pressure (see page 11-131). Is it normal? YES - Go to step 5. NO - Check for fuel supply system (see page 11-287). Let it idle for at least 1 minute before test-driving. Open the throttle wide open, then quickly release it. Measure voltage between ECM/PCM connector terminals A10 and A25 (E2 and E4)*. ECM/PCM CONNECTORS Wire side of female terminals

Is the voltage above 0.6 V at wide open throttle to 4,500 rpm (min-1) and below 0.4 V when the throttle is quickly released from 4,500 rpm (min-1)? YES - Substitute a known-good ECM/PCM and recheck. If symptom/indication goes away, replace the original ECM/PCM. NO - Go to step 7. Turn the ignition switch OFF. Disconnect the secondary HO2S (Sensor 2) 4P connector. At the secondary HO2S (Sensor 2) harness side, connect the battery positive terminal to terminal No. 4 and battery negative terminal to terminal No. 3. Start the engine. After 2 minutes, measure voltage between secondary HO2S (Sensor 2) 4P connector terminals No. 1 and No. 2. SECONDARY HO2S 4P CONNECTOR Wire side of female terminals Is the voltage above 0.6 V at wide open throttle to 4,500 rpm (min-1) and below 0.4 V when the throttle is quickly released from 4,500 rpm (min-1)? YES - Repair open or short in the wire between the ECM/PCM (A10, A25) (E2, E4)* and the secondary HO2S (Sensor 2). NO - Replace the secondary HO2S (Sensor 2) (see page 11-279).