Precautions

When perform diagnosis procedure, observe the following cautions:
1. Before connecting or disconnecting ECU harness connector, ensure ignition switch is in the ``Off'' position and battery ground cable is disconnected.
2. When performing input/output signal inspection, remove pin terminal retainer from 20-pin and 16-pin connector to facilitate inserting tester probe into connector.
3. When connecting or disconnecting terminals from ECU, use caution not to bend or break pin terminals.
4. Before replacing ECU, perform input/output signal inspection to ensure whether ECU operates satisfactorily.
5. When measuring supply voltage of ECU controlled components with a circuit tester, use caution not to touch two tester probes together during measurement or circuit may become damaged.
6. When measuring voltage or resistance at a electrical connector with tester probes, there are two methods of measurement; one is done from terminal side (observe TS symbol) and the other from harness side (observe HS symbol).



Input/Output Signal Diagnosis

1. Disconnect battery ground cable.
2. Disconnect 16-pin and 20-pin connectors from ECU and remove pin terminal retainer form connectors.
3. Connect 16-pin and 20-pin connectors to ECU, then connect battery ground cable.
4. Measure voltage at each terminal by following ECU input/output signal inspection chart, Figs. 299 through 309. Do not touch tester probes between terminals 27 and 28 or 35 and 36.