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Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 60 (Engine Controls [Self-Diagnostics 2.3L]) >> Diagnostic Tests >> DTC P0403: EGR Valve (Stepper Motor) Circuit Malfunction >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
  1. If FREEZE FRAME DATA has been recorded, go to next step. If FREEZE FRAME DATA has not been recorded, record FREEZE FRAME DATA. Go to next step.
  2. Verify Related Repair Information Availability -  Check for related Service Bulletins and/or on-line repair information availability. If any related repair information is available, perform repair or diagnosis according to available repair information. If vehicle is not repaired, go to next step. If related repair information is not available, go to next step.
  3. Inspect EGR Valve Connector For Poor Connection -  Disconnect EGR valve 6-pin harness connector. Check for poor connection (such as damaged, pulled-out terminals, corrosion). If malfunction is not present, go to next step. If any malfunction is present, repair terminal. After repair, go to step  10.
  4. Inspect Power Circuit For Open Circuit -  Turn ignition on, engine off. Measure voltage between body ground and following terminals:
    • EGR valve 6-pin harness connector terminal "C" (White wire).
    • EGR valve 6-pin harness connector terminal "D" (White wire).
    If battery voltage is present, go to next step. If battery voltage is not present, repair open circuit in suspected wire or replace wire harness. See Fig 1. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. After repair, go to step  10.
    Fig 1: Identifying EGR Valve Stepper Motor Circuits & Harness Connector Terminals
    G00221507Courtesy of MAZDA MOTORS CORP.
  5. Inspect EGR Valve -  Perform EGR valve inspection. EXHAUST GAS RECIRCULATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. If EGR valve is okay, go to next step. If EGR valve is faulty, replace EGR valve. After repair, go to step  10.
  6. Inspect For Control Circuit For Short To Ground -  Turn ignition off. Check for continuity between body ground and following terminals:
    • EGR valve 6-pin harness connector terminal "E" (Red/Green wire)
    • EGR valve 6-pin harness connector terminal "A" (Pink wire)
    • EGR valve 6-pin harness connector terminal "B" (Gray wire)
    • EGR valve 6-pin harness connector terminal "F" (Yellow wire)
    If continuity is not present, go to next step. If continuity is present, repair short circuit to ground in suspected wire or replace wire harness. After repair, go to step  10.
  7. Inspect For Control Circuit For Short To Power -  Turn ignition on, engine off. Measure voltage between body ground and following terminals:
    • EGR valve 6-pin harness connector terminal "E" (Red/Green wire)
    • EGR valve 6-pin harness connector terminal "A" (Pink wire)
    • EGR valve 6-pin harness connector terminal "B" (Gray wire)
    • EGR valve 6-pin harness connector terminal "F" (Yellow/Green wire)
    If battery voltage is not present, go to next step. If battery voltage is present, repair short circuit to power in suspected wire or replace wire harness. After repair, go to next step.
  8. Inspect PCM Connector For Poor Connection -  Turn ignition off. Disconnect PCM harness connectors. Check for poor connection (such as damaged, pulled-out terminals, corrosion). If malfunctions are not present, go to next step. If any malfunctions are present, repair or replace terminal. After repair, go to step  10.
  9. Inspect Control Circuit For Open Circuit -  Disconnect PCM harness and EGR valve connectors. Check for continuity between following terminals:
    • Between EGR valve 6-pin harness connector terminal "E" and PCM 30-pin harness connector terminal "4E" (Red/Green wire)
    • Between EGR valve 6-pin harness connector terminal "A" and PCM 30-pin harness connector terminal "4H" (Pink wire)
    • Between EGR valve 6-pin harness connector terminal "B" and PCM 30-pin harness connector terminal "4K" (Gray wire)
    • Between EGR valve 6-pin harness connector terminal "F" and PCM 30-pin harness connector terminal "4N" (Yellow/Green wire)
    If continuity is present, go to next step. If continuity is not present, repair open circuit in suspected wire or replace wire harness. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. After repair, go to next step.
  10. Verify Trouble Shooting Of DTC P0403 Is Completed -  Make sure to reconnect all disconnected connectors. Clear DTC from PCM memory using WDS or equivalent. Turn ignition off. Start engine and warm it up completely. If PENDING CODE of same DTC is not present, go to next step. If PENDING CODE of same DTC is present, replace PCM. For PCM removal and installation, see POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION article. After repair, go to next step.
  11. Verify After Repair Procedure -  Using scan tool, perform After Repair Procedure. See AFTER REPAIR PROCEDURE . If any DTCs are present, go to appropriate DTC inspection. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are present, trouble shooting is complete.
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