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Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 69 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0040, DTC P0041, DTC P1128 Or DTC P1129 >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Mazda Tribute. However, it is still accessible from the selected car via links, so may be relevant.
  1. If QUICK TEST was not performed, go to QUICK TEST  under SELF-DIAGNOSTIC SYSTEM. If QUICK TEST was performed, go to next step.
  2. Inspect HO2S Harness Connectors -  Visually inspect vehicle front HO2S harness connector(s) (P0040 or P1128) or rear HO2S harness connector(s) (P0041 or P1129) for any indication of being crossed (stretched wires, wire harnesses not mounted properly). If there are no crossed connections or wires, go to next step. If there are any crossed connections or wires, repair as necessary. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step  4.
  3. Verify Proper HO2S SIG PIN Location -  Disconnect PCM 104-pin harness connector. Connect Breakout Box (49-UN01-130) to PCM harness connector only. See Fig 1. For DTC P0040 or P1128, disconnect both front HO2Ss from vehicle harness connectors.
    • HO2S-11 (Front Bank 1): breakout box terminal No. 60.
    • HO2S-21 (Front Bank 2): breakout box terminal No. 87.

    For DTC P0041 or P1129, disconnect both rear HO2Ss from vehicle harness connectors.

    • HO2S-12 (Rear Bank 1): breakout box terminal No. 35.
    • HO2S-22 (Rear Bank 2): breakout box terminal No. 61.

    Measure resistance of HO2S signal circuits between appropriate breakout box terminals and HO2S 4-pin harness connector. If resistance reading is more than 5 ohms, go to next step. If resistance reading is less than 5 ohms, problem is intermittent. Refer to INTERMITTENT  testing under SYSTEM TESTS.

    Fig 1: Identifying 104-Pin Break Out Box
    G00127421Courtesy of MAZDA MOTORS CORP.
  4. Verify Trouble Shooting Of DTCs Completed -  Reconnect all disconnected connectors. Clear DTCs from PCM memory using scan tool. Perform QUICK TEST  under SELF-DIAGNOSTIC SYSTEM. If same DTC is present, replace faulty PCM. Repeat QUICK TEST  under SELF-DIAGNOSTIC SYSTEM. If same DTC is not present, go to applicable procedure for other DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are present, trouble shooting is complete.
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