DTC P0135 Or DTC P0141: Ho2S Heater Circuit Malfunction

NOTE: DTC P0135 is set when a fault is detected in primary HO2S-1 circuit. DTC P0141 is set when a fault is detected in secondary HO2S-2 circuit.

Perform PCM reset procedure. See SELF-DIAGNOSTICS - INTRODUCTION article. Start engine. If DTC P0135 or P0141 is indicated, go to next step. If DTC P0135 or P0141 is not indicated, problem is intermittent. System is okay at this time. Check for poor connections or loose wires at suspect HO2S and PCM connectors. Also check for poor connections or loose wires at Green, 22-pin C127 connector located behind right kick panel, on PCM bracket. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
Turn ignition off. Disconnect suspect HO2S 4-pin connector. Measure sensor resistance between suspect HO2S connector terminals No. 3 and No. 4. See Figure . If resistance is 10-40 ohms, go to next step. If resistance is not 10-40 ohms, replace suspect HO2S.
Check for continuity between ground and suspect HO2S connector terminals No. 3 (Black/Yellow wire on HO2S-1; Black/White wire on HO2S-2) and No. 4 (Black/White wire), individually. See Figure . If continuity exists, replace suspect HO2S. If continuity does not exist, go to next step.
Turn ignition on. Measure voltage between suspect HO2S harness connector terminals No. 3 (Black/Yellow wire on HO2S-1; Black/White wire on HO2S-2) and No. 4 (Black/White wire). If battery voltage exists, go to next step. If battery voltage does not exist, go to step 7 .
Turn ignition off. If checking HO2S-1 (DTC P0135), disconnect PCM 31-pin connector "C". Check for continuity between ground and PCM 31-pin connector "C" terminal No. 1 (Black/White wire). See Figure . See appropriate wiring diagram in WIRING DIAGRAMS article. If checking HO2S-2 (DTC P0141), disconnect PCM 32-pin connector "A". Check for continuity between ground and PCM 32-pin connector "A" terminal No. 8 (Black/White wire). See Figure . See appropriate wiring diagram in WIRING DIAGRAMS article. Go to next step.
If continuity exists, repair short in Black/White wire between suspect HO2S and PCM. If continuity does not exist, substitute a known-good PCM and recheck. See SUBSTITUTING PCM in SELF-DIAGNOSTICS - INTRODUCTION article. If symptom or indication goes away, replace original PCM.
If checking HO2S-1 (DTC P0135), measure voltage between ground and HO2S-1 harness connector terminal No. 3 (Black/Yellow wire). See Figure . If checking HO2S-2 (DTC P0141), measure voltage between ground and HO2S-2 harness connector terminal No. 4 (Black/White wire). See Figure . If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short in wire between suspect HO2S connector and No. 15 ALTERNATOR SP SENSOR (7.5-amp) fuse. See appropriate wiring diagram in WIRING DIAGRAMS article.
Turn ignition off. Reconnect HO2S 4-pin connectors. If checking HO2S-1 (DTC P0135), disconnect PCM 31-pin connector "C". Turn ignition on. Using backprobe set, measure voltage between PCM 25-pin connector "B" terminal No. 2 (Black wire) and PCM 31-pin harness connector "C" terminal No. 1 (Black/White wire). See Figure and Figure . See appropriate wiring diagram in WIRING DIAGRAMS article. If checking HO2S-2 (DTC P0141), disconnect PCM 32-pin connector "A". Using backprobe set, measure voltage between PCM 25-pin connector "B" terminal No. 2 (Black wire) and PCM 32-pin harness connector "A" terminal No. 8 (Black/White wire). See Figure . See appropriate wiring diagram in WIRING DIAGRAMS article. Go to next step.
If voltage is 0.1 volt or less, repair open in Black/White wire between suspect HO2S and PCM. See appropriate wiring diagram in WIRING DIAGRAMS article. If voltage is more than 0.1 volt, substitute a known-good PCM and recheck. See SUBSTITUTING PCM in SELF-DIAGNOSTICS - INTRODUCTION article. If symptom or indication goes away, replace original PCM.