Diagnostic Procedure
- Verify Related Repair Information Availability -
Turn ignition off. Connect scan tool to DLC-2. See Figure. 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 Neutral Switch Signal Circuit For Short To GND -
Turn ignition off. Disconnect neutral switch single pin harness connector terminal "A". See Fig 1. Measure voltage between ground and neutral switch harness connector terminal "A" (Violet wire). If voltage is not present, go to next step. If voltage is present, repair short circuit to ground in Violet wire between neutral switch harness connector terminal "A" and PCM 31-pin harness connector terminal "4H". See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step 8.
- Inspect Poor Connection Of Neutral Switch Connector -
Disconnect single pin harness connector terminal "B" (Black wire). Check for poor connection at neutral switch single pin connectors terminals "A" and "B" due to damaged, pulled-out pins, corrosion, etc. If connector terminals are okay, go to next step. If connector terminals are found faulty, repair or replace as necessary. After repair, go to step 8.
- Inspect Neutral Switch GND Circuit For Open -
Check continuity between ground and neutral switch harness connector terminal "B" (Black wire). 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 "B" and body ground single ring terminal. After repair, go to step 8.
- Inspect Poor Connection Of PCM Connector -
Disconnect PCM 31-pin harness connector. See Fig 1. Check for poor connection at PCM connector terminals due to damaged, pulled-out pins, corrosion, etc. If connector terminals are okay, go to next step. If connector terminals are found faulty, repair or replace as necessary. After repair, go to step 8.
- Inspect Neutral Switch Signal Circuit For Open -
Check continuity between neutral switch harness connector terminal "A" and PCM 31-pin harness connector terminal "4H" (Violet wire). If continuity is present, go to next step. If continuity is not present, repair open circuit in Violet wire between neutral switch harness connector terminal "A" and PCM 31-pin harness connector terminal "4H". After repair, go to step 8.
- Inspect Neutral Switch -
Perform neutral switch inspection. See 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 next step. If neutral switch is faulty, replace neutral switch. After repair, go to next step.
- Verify Troubleshooting Of DTC P0850 Completed -
Return vehicle to original condition. Using scan tool, clear DTCs from PCM memory. 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 P0850 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.
- 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, go to applicable test and repair.
Courtesy of MAZDA MOTORS CORP.