System Testing

When performing component testing procedures the following precautions must be taken:
1. A high impedance digital type voltmeter must be used for accurate measurement.
2. The voltmeter negative probe should always be connected to a body or engine ground.
3. When disconnecting the Electronic Control Module (ECM) always make sure the ignition switch is turned off, and never connect a tester to the Engine Control Module (ECM) when it is disconnected.

Fig. 116 Connections For ECM Voltage Test:

Fig. 117 Proper Connection Of Test Probe From Back Side Of Connector:

4. Check voltage at the ECM connector by making test connections as shown Fig. 116. Make test probe to terminal connections as shown in Fig. 117. If test probe must be connected from terminal side of the connector, make connections as shown in Fig. 118, use caution not to bend the male terminal and never force the female terminal opening to make a test connection.

Fig. 118 Proper Connection Of Test Probe From Terminal Side Of Connector:

5. For accurate test readings, always make sure battery voltage is eleven volts or higher. Failure to follow these test precautions may cause damage to the ECM and/or connector terminals, and may allow for improper system diagnosis.
6. Prior to accessing trouble codes from the ECM, never disconnect battery cables, ECM connectors, ECM ground wire harness from engine or main fuse. Disconnecting any of these circuits will cause the ECM memory to be erased.