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. Conduct tests with engine at operating temperature unless instructed otherwise.

TESTING WITH SIGNAL MONITOR

1. Connect signal monitor between ECU and wiring harness using correct adapter (#49 G018 903).

NOTE: Use adapter connector "A" to measure voltage at terminals 1A through 1V and 3A through 3Z. Use connector "B" to measure at terminals 2A through 2P.

2. Place cover sheet on signal monitor face (#49 G018 904, 64 pin side).
3. Turn selector and monitor switches to select desired terminal number and measure voltage.
4. If any terminal voltage is incorrect, check the input or output device and related wiring. Only replace an ECU if other possible causes of abnormal voltages are eliminated.

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

ECU TESTING PRECAUTIONS [1]

1. If factory test equipment is not available, use only digital volt/ohm meter with minimum 10Meg ohms internal impedance for testing ECU terminal voltages.
2. Never push circuit tester probes into connectors from ECU side.
3. Before replacing an ECU, check components, wiring harnesses and terminal contacts. If terminal voltage readings are incorrect, check for other possible causes (lower than normal or zero voltage may indicate a short to ground in wiring. Higher than normal voltage may indicate an open circuit in wiring between that terminal and the corresponding input/output device, or a poor connection within a harness connector.) Repair as needed and recheck voltage readings.

[1] For more complete information on special precautions regarding handling and testing of electronic components, Vehicle Damage Warnings

ECU Pin/Voltage Chart (1 Of 4):

ECU Pin/Voltage Chart (2 Of 4):

ECU Pin/Voltage Chart (3 Of 4):

ECU Pin/Voltage Chart (4 Of 4):

ECU TERMINAL VOLTAGE CHARTS

ECU Connector/terminal ID:

ECU CONNECTOR TERMINAL ID