Engine Control Module: Testing and Inspection

ECU Testing:

The Mazda Engine Signal Monitor (#49 9200 162) is utilized to check ECU terminal voltages. This tool inspects individual terminal voltages as selected with the monitor switch. A high impedance volt/ohm meter can also be used to check these voltages. Aftermarket test units are available that will read ECU terminal voltages when connected with proper adapters.

To use the Engine Signal Monitor, connect unit between ECU and wiring harness with the correct adapter (#49 G018 903). Place pin number cover sheet (#49 G018 904) on monitor face. Turn select and monitor switches to the desired terminal number for a voltage readout. Conduct tests with engine at operating temperature unless instructed otherwise.

CAUTION: Never apply voltage to terminals "A" and "B."

ECU TESTING PRECAUTIONS

1. Never push circuit tester probes into connectors from ECU side.
2. Before replacing an ECU, check components, wiring harnesses and terminal contacts if terminal voltage readings are incorrect. Repair as needed and recheck voltage readings.

ECU PIN VOLTAGE CHART

Part 1

Terminal Voltage Chart (Part 1):

Part 2

Terminal Voltage Chart (Part 2):

Part 3

Terminal Voltage Chart (Part 3):

Part 4

Terminal Voltage Chart (Part 4):

DECHOKE CONTROL SYSTEM

Dechoke Control System Testing:

1. Check that coolant temperature is below 0°C (32°F).
2. If not, disconnect water thermosensor and connect an approximately 10K ohms resistor across harness terminals.
3. Turn ignition switch to "START" and verify that injector operating sounds (clicking) are heard.
4. Depress accelerator pedal fully and turn ignition switch to "START." Check that there are now no injector operating sounds.
5. If not as specified, check wiring, connectors and individual components such as water thermosensor, throttle sensor and injectors.