MPI Control Relay
- This step checks ignition switch supply voltage of control relay. Disconnect control relay connector. Turn ignition on. Using DVOM, measure voltage between terminal No. 5 of relay harness connector and vehicle ground. See Fig 1
. If voltage is battery voltage, go to step 2. If voltage is not battery voltage, check and repair circuit between ignition switch and control relay.
- This step checks continuity of control relay ground circuit. Turn ignition off. Using DVOM, check continuity between control relay harness connector terminal No. 7 and vehicle ground. If continuity exists, go to step 3. If continuity does not exist, check and repair circuit between control relay and vehicle ground.
- This step checks battery supply voltage of control relay. Using DVOM, measure voltage between terminal No. 1 of relay harness connector and vehicle ground. If voltage is battery voltage, go to step 4. If voltage is not battery voltage, check and repair circuit between battery and control relay.
- This step checks continuity of circuit between control relay and ECM. Disconnect ECM connector. Check continuity between control relay harness connector terminal No. 2 and ECM terminals No. 2 and 15 of connector C50-4 on California models or terminals No. 9 and 4 of connector C50-3 on Federal models. See Figure
, Figure
and Fig 1
.
- If continuity exists, harness is okay. Go to step 6. If continuity does not exist, check and repair circuits between control relay harness connector and ECM.
- This step checks continuity of control relay. Removal of relay may assist in testing. Measure resistance between terminals No. 2 and 8 and between terminals No. 3 and 8. Resistance should be about 95 ohms. Measure resistance between terminals No. 6 and 7. Resistance should be about 35 ohms. Measure resistance between terminals No. 5 and 7. Continuity should exist in only one direction. Replace control relay if any measurements are not as specified.
- Connect 12-volt power source between relay terminals No. 6 and 7. Connect positive lead to terminal No. 6. With relay energized, continuity should exist between terminals No. 1 and 4. With power source removed, continuity should not exist.
- Move 12-volt power source to relay terminals No. 5 and 7. Connect positive lead to terminal No. 5. With relay energized, continuity should exist between terminals No. 1 and 3. With power source removed, continuity should not exist. Replace control relay if any measurements are not as specified.
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.