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 (Rear) Connector For Poor Connection - Turn ignition off. Disconnect rear HO2S 4-pin 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 (Rear) - Measure resistance between rear HO2S 4-pin connector terminals "C" and "D". See Fig 1. If resistance reading is about 15.7 ohms, go to next step. If resistance reading is not as specified, replace rear HO2S. After repair, go to step 8.
- Inspect HO2S Heater (Rear) Power Circuit For Open Circuit - Turn ignition on, engine off. Measure voltage between ground and rear HO2S 4-pin harness connector terminal "C" (Black/Blue wire). See Fig 2. If battery voltage is present, go to next step. If battery voltage is not present, check for open in circuit between ignition switch and rear HO2S. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. Go to step 8.
- Inspect PCM Connector For Poor Connection - Turn ignition off. Disconnect PCM 104-pin harness connector. See Figure. Check for poor connection due to damaged, pulled-out terminals, corrosion, etc. Repair as necessary, and go to step 8. If connector terminals are okay, go to next step.
- Inspect HO2S Heater (Rear) Control Circuit For Short To Ground - Check for continuity between ground and rear HO2S 4-pin harness connector terminal "D" (Green/Red wire). See Fig 2. If continuity is not present, go to next step. If continuity is present, repair short circuit to ground in Green/Red wire between rear HO2S 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 93. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step 8.
- Inspect HO2S Heater (Rear) Control Circuit For Open Circuit - Connect 104-pin Breakout Box (49-UN01-130) to PCM harness connector only. See Figure. Check for continuity between rear HO2S 4-pin harness connector terminal "D" (Green/Red wire) and breakout box terminal No. 93. See Fig 2. If continuity is present, go to next step. If continuity is not present, repair open circuit in Green/Red wire between rear HO2S 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 93. After repair, go to next step.
- Verify Trouble Shooting Of DTC P0037 Completed - Reconnect all connectors. Turn ignition on, engine off. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. Start engine and allow it to reach normal operating temperature. Monitor for DTCs. If DTC P0037 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 P0037 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 .