Diagnostic Strategies

Fig. 5 ECI diagnostic test connector. 1984-86:

Fig. 6 Self diagnosis signal indicating system is normal:

Fig. 7 Self diagnosis signal indicating a system malfunction:

Fig. 9 Input signal diagnosis chart. 1985-86 Conquest:

Refer to ``Pre-Test Conditions'' before performing procedure.
Turn ignition switch to Off position, then connect a voltmeter between ``self-diagnosis output'' and ``ground'' terminals of connector, Fig. 5, located in engine compartment. Turn ignition switch On. An indication of ECU memory will immediately begin. Input signal malfunctions are indicated by voltmeter pointer deflection. If the system is in the normal condition, voltmeter will read a constant 12 volts, Fig. 6. When input signal is abnormal, pointer deflection alternates between 0 volts and 12 volts every .4 seconds with a 2 second lag between each abnormal code. For example, constant pointer deflection between 0 volts and 12 volts every .4 seconds, indicates abnormal engine speed, code 8; pointer deflection between 0 volts and 12 volts twice for .4 seconds with a two second lag, then repeated, indicates code 2, abnormal ignition pulse. The diagram shown, Fig. 7, indicates codes 2 and 5 are abnormal. Malfunctions can be identified by observing pulses on voltmeter and comparing them to ECI diagnosis chart, Fig. 9.
After recording each malfunction, repair as necessary items listed in ``check item'' column in diagnosis chart. Turn ignition switch Off. Disconnect battery ground cable to erase malfunctions from computer memory, then road test vehicle and ensure all malfunctions have been repaired.