Diagnostic Procedure
- Turn ignition off. Connect New Generation Star (NGS) tester or equivalent to OBD-II Data Link Connector (DLC-2). See Figure. Turn ignition on. Monitor for FREEZE FRAME DATA and ensure data has been recorded. Check for service bulletins and/or other line of repair information related to this DTC. If repair information is available, perform diagnosis and repair as necessary. After repair, go to step 7. If repair information is not available, go to next step.
- Turn ignition off. 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 7.
- With PCM harness connector disconnected, turn ignition on. Measure voltage between ground and PCM harness connector terminal "4Z" (Pink/Black wire). Voltage should be 4.5-5.5 volts. If voltage is as specified, go to next step. If voltage is not as specified, repair open circuit (in Pink/Black wire) between TCM and PCM. After repair, go to step 7.
- Turn ignition off. Leave PCM harness connector disconnected and disconnect TCM 36-pin harness connector. See Fig 1. Check for poor connection at TCM 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 7.
- Reconnect PCM harness connector and Leave TCM harness connector disconnected, turn ignition on. Measure voltage between ground and TCM harness connector terminal "AL" (Violet/Green wire). Voltage should be 4.5-5.5 volts. If voltage is as specified, go to next step. If voltage is not as specified, repair open or short circuit (in Violet/Green wire) between TCM and PCM. For circuit identification, see MIATA
in WIRING DIAGRAMS article. After repair, go to step 7.
- Return vehicle to original condition. Perform TCM DTC inspection and voltage inspection. If TCM is okay, go to next step. If TCM is faulty, replace TCM. After repair go to next step.
- Return vehicle to original condition. Using NGS tester or equivalent, clear DTCs from PCM memory. Start engine and let it idle until it reaches normal operation temperature. Monitor for DTCs. If same DTC P1601 is present, replace PCM. For PCM removal and installation, see POWERTRAIN CONTROL MODULE
in REMOVAL, OVERHAUL & INSTALLATION article. If any other DTC is present, follow appropriate DTC diagnostic procedure.
Courtesy of MAZDA MOTORS CORP.