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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. Classify High Input Or Low Input -  Connect WDS or equivalent to DLC-2. Access CPP/PNP PID. Verify CPP/PNP PID when gear in neutral position. If CPP/PNP PID is always OFF, go to next step. If CPP/PNP PID is not always OFF, go to step  10.
  4. Inspect Neutral Switch Connector For Poor Connection -  Turn ignition off. Disconnect neutral switch harness connector. Check for poor connection (such as damaged, pulled-out terminals or corrosion). If malfunction is present, repair or replace terminal. After repair, go to step  14.
  5. Classify Neutral Switch Or Circuit -  Connect WDS or equivalent to DLC-2. Access CPP/PNP PID. Connect fused jumper wire between neutral switch harness connector terminal "A" (Black wire) and terminal "B" (Blue/Red wire). If CPP/PNP PID is ON, go to next step. If CPP/PNP PID is not ON, go to step  7.
  6. Inspect Neutral Switch -  Perform Neutral Switch Inspection. Refer to NEUTRAL SWITCH (M/T) under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. If neutral switch is okay, go to step  14. If neutral switch is faulty, replace Neutral switch. After repair, go to step  14.
  7. Inspect Neutral Switch Ground Circuit For Open Circuit -  Check for continuity between neutral switch harness connector terminal "A" (Black wire) and body ground. See Fig 1. If continuity is present, go to next step. If continuity is not present, repair open circuit in Black wire between Neutral switch harness connector terminal "A" and body ground or replace wire harness. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. After repair, go to step  14.
    Fig 1: Identifying Neutral Switch Circuits & Harness Connector Terminals
    G00221558Courtesy of MAZDA MOTORS CORP.
  8. Inspect PCM Connector For Poor Connection -  Turn ignition off. Disconnect PCM 104-pin harness connector. Inspect for poor connection (such as damaged, pulled-out terminals or corrosion). If malfunction is not present, go to next step. If malfunction is present, repair terminal or replace wire harness. After repair, go to step  14.
  9. Inspect Neutral Switch Signal Circuit For Open Circuit -  Check for continuity in Blue/Red wire between neutral switch harness connector terminal "B" and PCM 104-pin harness connector terminal No. 64. If continuity is present, go to step  14. If continuity is not present, repair open circuit in Blue/Red wire between neutral switch harness connector terminal "B" and PCM 104-pin harness connector terminal No. 64. After repair, go to step  14.
  10. Inspect Neutral Switch Connector For Poor Connection -  Turn ignition off. Disconnect neutral switch harness connector. Inspect for poor connection (such as damaged, pulled-out terminals or corrosion). If malfunction is not present, go to next step. If malfunction is present, repair terminal or replace wire harness. After repair, go to step  14.
  11. Classify Neutral Switch Or Circuit -  Connect WDS or equivalent to DLC-2. Access CPP/PNP PID. Ensure CPP/PNP PID changes from ON to OFF when neutral switch harness connector is disconnected. If CPP/PNP PID changes from ON to OFF, go to next step. If CPP/PNP PID does not change from ON to OFF, go to step  13.
  12. Inspect Neutral Switch -  Perform Neutral Switch Inspection. Refer to NEUTRAL SWITCH (M/T) under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. If neutral switch is okay, go to step  14. If neutral switch is faulty, replace neutral switch. After repair, go to step  14.
  13. Inspect Neutral Switch Signal Circuit For Short To Ground -  Check for continuity in Blue/Red wire between neutral switch harness connector terminal "B" and body ground. See Fig 1. If continuity is not present, go to next step. If continuity is present, repair short circuit in Blue/Red wire between neutral switch harness connector terminal "B" and PCM 104-pin harness connector terminal No. 64. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. After repair, go to next step.
  14. Verify Trouble Shooting Of DTC P0850 Is Completed -  Reconnect all connections. Start engine. Clear DTC from memory using WDS or equivalent. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine and let idle until normal operating temperature is reached. Drive vehicle at 18.6 MPH or more. Shift up or down 14 times during test drive. Monitor for DTCs. If same DTC is not present, go to next step. If same DTC 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.
  15. 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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