ECC System (Federal)

Fig. 15 ECC unit diagnostic switch & indicator lamps:

1. Position ECC control unit so red and green inspection lamps are visible. The control unit is located under the driver's seat.
2. Start engine and run until normal operating temperature is reached.
3. Ensure diagnosis switch on ECC unit, Fig. 15, is in Off position.
4. Run engine at 2000 RPM for approximately five minutes under no load, then observe green inspection lamp while maintaining engine speed. If green lamp cycles on and off more than five times in ten seconds, proceed to step 6. If lamp does not cycle as indicated, proceed to step 5.

Fig. 16 Exhaust gas sensor circuit continuity test:

5. Check exhaust gas sensor harness as follows:
a. Turn engine off, then disconnect battery ground cable and the 20-pin connector from ECC control unit.
b. Disconnect exhaust gas sensor electrical connector and ground the connector using a suitable jumper wire.
c. Check for continuity between 20-pin connector terminal 2 and ground, Fig. 16. If continuity exists, replace exhaust gas sensor. If continuity does not exist, repair or replace ECC harness as necessary.
d. Repeat ECC system diagnosis.
6. Turn engine off, then move diagnosis switch on ECC unit to the On position.
7. Turn ignition switch On and observe red and green inspection lamps on ECC unit.
8. If the green lamp is lit and the red lamp is not, the system is functioning normally. If the red lamp is lit and the green lamp cycles on and off (remaining on longer than off), proceed to step 10. if the red lamp is lit and the green lamp cycles on and off (remaining off longer than on), proceed to step 9.

Fig. 17 Vacuum sensor location (typical):

Fig. 18 Vacuum sensor test connections:

9. Check individual sensors as follows:
a. With ignition switch off, ensure all harness connectors are secure, correcting as needed.
b. Disconnect 20-pin connector from ECC control unit.
c. On 1983-86 models, connect terminal 20 to battery positive terminal and terminal 19 to battery negative terminal.
d. On all models, disconnect vacuum sensor hose and connect a suitable hand vacuum pump to the sensor, Figs. 17 and 18.

Fig. 19 Sensor test connections & specifications:

e. Turn ignition switch to On position, then connect 12 volts to sensor terminals and check output voltage, Fig. 19. If voltage is not within specifications, replace vacuum sensor and recheck system. If voltage is within specifications, proceed to step e.
f. Disconnect electrical connectors from water temperature sensor and air temperature sensor and measure resistances outlined in Fig. 19. If resistance(s) is not within specifications, replace sensor(s) and recheck system. If resistances are within specifications, repair or replace ECC harness as necessary.

Fig. 20 Solenoid test specifications.:

Fig. 21 Solenoid test specifications.:

10. Check individual components as follows:
a. With ignition switch off, ensure all harness connectors are secure, correcting as needed.
b. Disconnect electrical connector from each component noted in Figs. 20 and 21 and measure resistance of each.
c. Replace any component whose resistance is not within specifications, then recheck system. If all resistances are within specifications, proceed to step d.

Fig. 22 Solenoid test connections.:

Fig. 23 Solenoid test connections.:

Fig. 24 Solenoid test connections.:

d. Reconnect electrical connectors to tested components, then disconnect 10 and 20-pin connectors from ECC unit.
e. Turn ignition switch on and measure voltage at terminals noted in Figs. 22 through 24. If any voltage is not within specifications, repair or replace harness. If all voltage readings are within specifications, replace ECC control unit and recheck system.