Camshaft Position Sensor (Miata)

NOTE: May require removal of PCM to gain access to wire terminals.

Remove and inspect Camshaft Position (CMP) sensor. Clean off any metal particles or shavings. Reinstall sensor.
Connect scan tool to DLC-2. Start engine. Using scan tool, enter vehicle information. Connect oscilloscope positive test lead to PCM 24-pin harness connector terminal "3V" (Gray/Blue wire) and negative test lead to 31-pin harness connector terminal "4A" (White/Red wire). See Fig 1 . Select DIGITAL MEASUREMENT SYSTEM, then FREQUENCY METER. Press link key to select RPM PID. Select PID/DATA MONITOR, then PCM. Press START.
Set oscilloscope to 2.0V/DIV (Y), 20ms/DIV (X), DC range. Inspect wave profile with engine idling. See Fig 2 . If wave profile or voltage are not as specified, check for short or open circuit between:
- CMP sensor 3-pin harness connector terminal "B" and PCM 24-pin harness connector terminal "3V" (Gray/Blue wire).
- CMP sensor 3-pin harness connector terminal "A" and main relay 4-pin harness connector terminal "D" through common connector (White/Red wire).
- CMP sensor terminal "C" and PCM 31-pin harness connector terminal "4A" (Black/Blue wire).
If open or short circuit are found repair or replace wiring harness as necessary. If short or open circuit are not found, replace CMP sensor. Check protrusion on intake camshaft for damage and cracks. Repair as necessary.

Fig 1: Identifying CMP Sensor Testing Terminals & Connector Views (Miata)
Courtesy of MAZDA MOTORS CORP.

Fig 2: Identifying CMP Sensor Waveform (Miata 1.8L)
Courtesy of MAZDA MOTORS CORP.

CMP/PCM TERMINAL IDENTIFICATION (PROTEGE)