Diagnostic Procedure
WARNING: This page is about a different car, the 2003 Mazda Protege5 and 2003 Mazda Protege. However, it is still accessible from the selected car via links, so may be relevant.
- Verify Related Repair Information Availability - Turn ignition off. Connect scan tool to DLC-2. Turn ignition on, engine off. Monitor for FREEZE FRAME DATA and ensure data has been recorded. Check service bulletins for repair information related to this DTC. If repair information is not available, go to next step. If repair information is available, perform diagnosis and repair as necessary. After repair, go to step 8.
- Inspect HO2S (Front) Connector For Poor Connection - Turn ignition off. Disconnect front HO2S 4-pin harness connector. Check for poor connection due to damaged, pulled-out terminals, corrosion, etc. Repair as necessary. After repair, go to step 8. If connector terminals are okay, go to next step.
- Inspect HO2S Heater (Front) - Measure resistance between front HO2S 4-pin connector terminals "C" and "D". See Fig 2. If resistance reading is about 5.6 ohms, go to next step. If resistance is not as specified, replace front HO2S. After repair, go to step 8.
- Inspect Power Circuit Of HO2S Heater (Front) For Open Circuit - Turn ignition to on, engine off. Measure voltage between ground and front HO2S 4-pin harness connector terminal "C" (Black/Blue wire). See Figure. If battery voltage is present, go to next step. If battery voltage is not present, repair open circuit in Black/Blue wire between ignition switch terminal "IG1" and front HO2S 4-pin harness connector terminal "C". See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step 8.
- Inspect PCM Connector For Poor Connection - Turn ignition off. Disconnect PCM 104-pin harness connector. See Fig 3. Check for poor connection due to damaged, pulled-out terminals, corrosion, etc. Repair as necessary. After repair, go to step 8. If connector terminals are okay, go to next step.
- Inspect Control Circuit Of HO2S Heater (Front) For Short To Ground - Check for continuity between ground and front HO2S 4-pin harness connector terminal "D" (Light Green/Red wire). See Figure. If continuity is not present, go to next step. If continuity is present, repair short circuit to ground in Light Green/Red wire between front HO2S 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 94. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step 8.
- Inspect Control Circuit Of HO2S Heater (Front) For Open Circuit - Connect 104-pin Breakout Box (49-UN01-130) to PCM harness connector only. See Fig 1. Check for continuity between front HO2S 4-pin harness connector terminal "D" (Light Green/Red wire) and breakout box terminal No. 94. If continuity is present, go to next step. If continuity is not present, repair open circuit in Light Green/Red wire between front HO2S 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 94. After repair, go to next step.
- Verify Trouble Shooting Of DTC P0031 Completed - Reconnect all connectors. Turn ignition on, engine off. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. Start engine and allow to reach normal operating temperature. Monitor for DTCs. If DTC P0031 is present, replace PCM. For PCM removal and installation, see POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION article. After repair, go to next step. If same DTC P0031 is not present, go to next step.
- Verify After Repair Procedure - Using scan tool, perform After Repair Procedure. See AFTER REPAIR PROCEDURE . If no other DTCs are present, testing is complete. If any other DTC is present, follow appropriate DTC diagnostic procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .