DTC P0135/P0141 - O2S Heater Circuit Malfunction

Install scan tool. Start engine and check if DTC P0135 or P0141 is present. If DTC is present, go to next step. If DTC is not present, problem is intermittent.
Turn ignition off. Disconnect affected O2S harness connector. Turn ignition on. Using DVOM, check voltage between affected O2S harness connector terminal No. 4 and ground. If battery voltage is present, go to next step. If battery is not present, check circuit between terminal No. 4 and fuel pump relay. See appropriate wiring diagram in WIRING DIAGRAMS section.
Turn ignition off. Disconnect ECM harness connector. Check for continuity between ECM terminal No. 12 (front O2S) or terminal No. 39 (rear O2S) and O2S harness connector terminal No. 1. If continuity is not present, check for open in circuit. If continuity is present, go to next step.
Reconnect ECM harness connector. Check for continuity between O2S harness connector terminal No. 2 and ground. Continuity should be present. If continuity is present, go to next step. If continuity is not present, check for open in circuit.
Disconnect affected O2S harness connector. Using a DVOM, check O2S heater resistance. With engine off, resistance should be 1.7-2.5 ohms. Replace O2S if resistance is not as specified. If resistance is okay, go to next step.
Reconnect O2S harness connector. Clear DTC. See CLEARING DTC(S) . Retest system. If DTC resets, replace ECM.