1993 Honda Civic DX--122,000 miles

Symptoms

Engine cranks but will not start. The “Check Engine Light” (MIL) stays on, along with the oil and battery lights. 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.

CroCivic91

That's a very nice and informative question.

Everything you did makes perfect sense. Also, the problem with CEL staying on is so common on this 5th generation civic, and i heard it so many times, but i never found a solution for it. Try to find a used ECM at a junk yard or something, and put it in. See if that helps.

Also, try to disconnect the battery's negative cable for 10-15 seconds, to clear the ECM from errors. See if CEL will get back on.

Other than those lousy suggestions, i don't have anything better to offer.

txgreasemonkey

I finally solved the problem, after 2-1/2 weeks of working on the car. All of the above symptoms were caused by the Manifold Absolute Pressure (MAP) Sensor. The ECM uses the MAP Sensor (transducer) to control fuel delivery and ignition timing. I turned the ignition on, disconnected the MAP connector, and used my DMM to check the reference and signal voltages (4.94v). Suddenly, when I went to record the readings, the fuel pump started to run. It blew me away! I got the fire extinguisher ready, just in case something weird was about to happen. When I pushed the clutch in and turned the ignition to start, it fired right up and ran beautifully. Therefore, the "Key Step" is to wait several minutes after you disconnect a sensor wire to see if the "Check Engine Light" goes out.

It's scary how vulnerable our cars are today. So much for Honda/Japanese reliability. As far as I'm concerned, this is poor engineering because MAP sensor failure is catastrophic--you lose both your ignition and fuel system. Failure to properly diagnose a faulty MAP sensor can easily lead you down a path that causes you to replace your main relay, ICM, coil, distributor, and ECM. This is the "Achilles Heel" of Honda Civics from this generation. Shame on Honda for not designing a more fault-tolerant system. A new MAP sensor from Honda, which is about 1" x 1" x 1-1/2", costs around $350.

CroCivic91, I'm glad you responded. I see you are from Zagreb. My wife served in the Bosnian War in Sarajevo and Zagreb, from 1993 through 1996. She used to wear a Kevlar vest, as she went down "Sniper's Alley" in Sarajevo. She's the only woman in the Air Force to receive the Air Combat Medal, for flying 14 combat missions over Bosnia. She would fly from Rhein-Mein AB, Germany. One of her not so fond memories was doing a "combat" takeoff from Sarajevo, under enemy fire. Gutsy lady.

CroCivic91

Yeah, Sarajevo is pretty close to Zagreb. Serbs did a lot of bad things in both my country and in Bosnia. We had a few serbian snipers here in Zagreb too...they were mostly thrown out the window when they were found. I was only 8 when the war started here, but i had my share of fears and bad stories. My girl is from Vukovar, which was devastated by serbs. Her parents took her and her brother with absolutely nothing but what they could all wear at the moment and managed to run out of Vukovar in the last minutes when it was still possible to get out. Ugh...bad memories. Makes me angry...

My hat goes off to your wife...it takes quite some courage to do such things.

Oh, and thanks for sharing your solution with us!

kean

good day
i have the same problem with my PH16 engine non vtec, i think its the same with D16A6.
By the way i am from the Philippines.
same symptoms as txgreasemonkey had stated,
i checked pin D19 and D21 and i only get more or less than 2V sometimes 3V.
i suspect that my ECM is bad but sometimes it does work, there are times that i turn the ignition to II and i will hear the click sound from the main relay, the fuel pump will run and goes out after 2 secs, and the CEL will turn off, and the engine will start.

but more often, the same symptoms as above occur. and the engine will not start.

please tell me what are the signs of a bad ECM, and where does it gets its ground?

i would want to get a used ECM but i doubt how long it will stay fine because it will be the same age as my ECM.

thanks

txgreasemonkey

The ECM grounds only through G101 on the thermostat housing. Make sure it is perfecto! Cardone remanufactured ECMs are as good as or better than OEM ECMs. Heat and vibration "fries" ECMs over time and water kills them fast.

Don't you mean your engine is the same as the D16Z6 engine?

latreche34

I have a similar problem, except my check engine light goes on and off normaly, there is spark and fuel, I even tried to read the ECU or ECM error codes it just display a steady Check engine light on test mode, any ideas???

txgreasemonkey

As the author of the original posting, your situation seems pretty different to me. Yes, you have a "crank but won't start" situation, but, from there, I don't see the similarities. You have spark and fuel, I had neither.

For starters, disconnect the MAP sensor connector, turn ignition ON, and check for 5 volts going between the reference wire (right) socket (+) and the main ECM ground on the thermostat housing. Let me know what you read.

CRX Vtech

some body please help me fast!!!!! i was driving down the dual carriage way in my 1991 crx vtech when it died on me, got it back to my house and checked it over, i have fuel i have spark i have compression timings good but it wont fire!!! please help me.

txgreasemonkey

Answer these 3 basic diagnostic questions for me:

1. When you turn the ignition switch to ON (not START), does the Check Engine Light (CEL) come on and then go off after 2 seconds?

2. When the CEL goes out, do you hear (or feel) the main relay "click"?

3. During the 2 second interval that the CEL is on, do you hear the fuel pump in the gas tank run?

Your answer to each question above:

1.

2.

3.