1993 Honda Civic DX--122,000 Miles
Symptoms. Engine cranks but will not start. “Check Engine Light” (MIL) stays on. When the service check connector terminals were jumped, the MIL did not indicate any Diagnostic Trouble Codes. You hear the first click from the main relay’s first relay, but not the second and third click from the main relay’s second relay. You do not hear the fuel pump run for 2 seconds, as you normally do. Additionally, there is no spark at the plugs.
Work Performed. I replaced the main relay with a new Mitsuba RZ-0159, because of the age of the vehicle and knowing they are problematic. It made no difference. When I jumped the 5th and 7th terminals on the main relay connector, I could hear the fuel pump run.
Using a digital multi-meter, all under-hood and under-dash fuses were determined to be good. The battery is 2 months old and fine. Turning the ignition on and individually disconnecting the 3P connector of the MAP sensor and the Throttle Position (TP) sensor did not cause the MIL to go out.
I disconnected the PGM-FI main relay connector. I checked for continuity between BLK Terminal 2 and body ground. There was continuity. I measured the voltage between YEL/WHT Terminal 1 and body ground (12.52v). Next, I turned the ignition switch on and measured the voltage between BLK/YEL Terminal 5 and body ground (12.52v). Continuity was also fine between GRN/YEL main relay Terminal 8 and ECM A7, A8, individually. The ECM grounding terminal on the thermostat was removed and cleaned, just to be safe.
Since there was no spark, I installed a new ICM (Igniter)—G.P. Sorensen, Part No. 115070; Coil—OEM, TEC, Part No. 30510-PT2-006; and Rotor—Borg Warner, Part No. D712. After installing these parts, there still was no spark. I suspect this model Honda will not spark, if the “Check Engine Light” stays on and there is a power or grounding issue with the ECM. A new Honda distributor housing was installed 20,000 miles ago, therefore I don’t suspect bad CKP, CYL, or TDC sensors. I confirmed 12.4v going from the ignition switch to the distributor. Distributor wiring and electrical readings checked out fine.
Conclusion. I suspect the ECM is either not receiving power or there’s a control grounding issue involving main relay Terminal 8 (to ECM A7, A8). The ECM controls the second relay, by applying or removing ground to main relay Terminal 8. It’s possible the ECM is bad, but I understand this is not likely on Hondas. I request your help in solving this difficult problem. Thanks in advance.
Symptoms. Engine cranks but will not start. “Check Engine Light” (MIL) stays on. When the service check connector terminals were jumped, the MIL did not indicate any Diagnostic Trouble Codes. You hear the first click from the main relay’s first relay, but not the second and third click from the main relay’s second relay. You do not hear the fuel pump run for 2 seconds, as you normally do. Additionally, there is no spark at the plugs.
Work Performed. I replaced the main relay with a new Mitsuba RZ-0159, because of the age of the vehicle and knowing they are problematic. It made no difference. When I jumped the 5th and 7th terminals on the main relay connector, I could hear the fuel pump run.
Using a digital multi-meter, all under-hood and under-dash fuses were determined to be good. The battery is 2 months old and fine. Turning the ignition on and individually disconnecting the 3P connector of the MAP sensor and the Throttle Position (TP) sensor did not cause the MIL to go out.
I disconnected the PGM-FI main relay connector. I checked for continuity between BLK Terminal 2 and body ground. There was continuity. I measured the voltage between YEL/WHT Terminal 1 and body ground (12.52v). Next, I turned the ignition switch on and measured the voltage between BLK/YEL Terminal 5 and body ground (12.52v). Continuity was also fine between GRN/YEL main relay Terminal 8 and ECM A7, A8, individually. The ECM grounding terminal on the thermostat was removed and cleaned, just to be safe.
Since there was no spark, I installed a new ICM (Igniter)—G.P. Sorensen, Part No. 115070; Coil—OEM, TEC, Part No. 30510-PT2-006; and Rotor—Borg Warner, Part No. D712. After installing these parts, there still was no spark. I suspect this model Honda will not spark, if the “Check Engine Light” stays on and there is a power or grounding issue with the ECM. A new Honda distributor housing was installed 20,000 miles ago, therefore I don’t suspect bad CKP, CYL, or TDC sensors. I confirmed 12.4v going from the ignition switch to the distributor. Distributor wiring and electrical readings checked out fine.
Conclusion. I suspect the ECM is either not receiving power or there’s a control grounding issue involving main relay Terminal 8 (to ECM A7, A8). The ECM controls the second relay, by applying or removing ground to main relay Terminal 8. It’s possible the ECM is bad, but I understand this is not likely on Hondas. I request your help in solving this difficult problem. Thanks in advance.
