Reading Diagnostic Trouble Codes

Fig. 3 MPI diagnosis test connection.:

Trouble code indications are made by reading voltmeter deflections. The voltmeter is connected to the self-diagnosis connector located in the glove box and if the indication is normal, the voltmeter will indicate a steady 12 volt reading. If diagnostic codes are present, the voltmeter will deflect between 0 and 12 volts. Compare the number of deflections with the diagnostic codes chart. When necessary to determine diagnostic codes, proceed as follows:

1. Turn ignition switch ``Off.''
2. Open the glove compartment, then locate the diagnostic connector.
3. Connect a suitable voltmeter between MPI terminal and ground. Fig. 3
4. Turn ignition switch ``On'' and note that an immediate indication of ECU memory contents will begin. If the system is in normal condition, the pointer of the voltmeter deflects as previously described and in the case of an abnormal condition, the voltmeter will deflect accordingly.
5. After recording the abnormal items, check and repair each part as directed.
6. Turn ignition switch ``Off.''
7. After repairs have been completed, disconnect battery ground cable for at least 15 seconds to erase abnormal code from memory.