Ignition Output Signal

I have a 1989 Honda Prelude SI, 5 speed, 2.0, FI, DOHC, that will not start. The LED in the ECU gives an error code 15, Ignition Output Signal. Voltages at the Igniter unit check OK per the Troubleshooting Flow Chart in my Honda Service Manual.

The error code 15 only shows after cranking the engine. After resetting the ECU, the error codes does not show again when the ignition switch is turned on, only after the engine is cranked. The troubleshooting flow chart says: “Intermittent failure, test drive may be necessary.” I surely would like to do a test drive, but the engine will not run.

Does anyone have any suggestions?

Thanks!

Is this the one that you just put the baro sensor in?

Hog Caller, I just wanted to know because like I stated early I have just never heard of a baro causing a no start.Years ago I had an emissions failure and called honda tech line and asked them about baro sensor.And they said it changed fuel trim but it was so little it wouldn,t cause a failure.That is why I wanted to know.Carl

Yes, it is the same Prelude. Initially I had two error codes, 13 and 15. The new baro sensor fixed the 13, however the engine still will not start and still dispalys error code 15, Ignition Output Signal.

Bair, do you still have a phone number for the Honda Tech line?

Here is what I would do.Find the blue wire on the ignitor.That is the output to the coil.Get a test light and put the clip on the battery positive terminal and the test side to the blue terminal on the ignitor.(I use a led light but this should work also).It should flash off and on when cranking.If it doesn,t I would replace the ignitor.It it does flash replace the coil.This how every honda tech I know checks a no start.I hope it helps you.Carl

Looks like you caught me in the middle of typing.No you have to be a honda tech to call and I opened my own shop in aug.So I can,t use it anymore either.Carl

Biar,

Thanks for your help! I will try your troubleshooting technique and post the results tomorrow night.

The two main things I have seen hondas towed in for are ignitor or coil.One more thing make sure, before you replace the ignitor that there is no spark.Because main relays can go bad too, but usually they will be intermidant.I will try to check in tommorow if you need more help.Carl

Thanks for all your help, however, I still have not resolved my ignition problem.

Checked the Main Relay and Main Relay Harness per the Honda Service Manual and found no problems.

Using a LED (I think the response of an incandescent bulb would be too slow), I made the following tests with the LED connected: positive-to-positive of battery and negative to Blue wire between Igniter and Coil.

With Key off, LED is lighted, with key on, LED is dark, when cranking, LED is dark (no flashing). The results are the same with the Blue wire not connected to the coil.

I made another test, which I think verifies the Coil and possibly the Igniter are OK.
With the Igniter connected to the coil and the white wire not connected to the ECU, I intimately grounded the Igniter White wire. When grounded the LED is lighted, when not, the LED is dark. I have a good ½ inch spark from the coil when the white wire is removed from the ground.

I checked the TDC and the Crank sensors per the service manual. They both have the proper resistance, 900 ohms. I verified continuity and no ground of all wires to the ECU.

What other possibilities exist except the ECU?

Hog Caller,Great job trouble shooting.I agree,with you ignitor and coil must be ok.What about the white wire while cranking? Carl

I was just looking at the wiring diagram.I believe you are right.If wires are fine what else is left.Again good job.Carl

Connected the LED: positive to positive of battery and negative connected to white wire between the igniter and ECU. Key off-LED dark, the instant the key is tuned on-one dim blink, key on-dark, and cranking-dark. Same results with white wire not connected to igniter.

Is there any way to check the output signal of the TDC and Crank sensors? Is there a possibility of a mechanical problem inside the distributor. Could the rotor-to-coil gap be off? Could a rotor drag a sensor and shear the roll pin? Is it worth pulling and dissambling the distributor? Other possibilities?

I think I would try.Looks like you going to put your meter between blue/yellow and white/blue and crank it over and see if there is a signal.Then orange/blue and blue/green and see if there is a signal.
I don,t want to state the odvious but the rotor is turning isn,t it.Also after your test.Go ahead and pull the dist and see if it turns freely the bearings were famous for going bad.It only goes back one way so you don,t have to worry about getting it in wrong.Carl

Will try to measure the output with a digital volt meter and go ahead and pull the distributor.

Assuming it looks good, do you have a reputable source for rebuilt ECU units that you care to recommend?

Removed the distributor and it looks great mechanically. Spun the distributer at 400 rpm in a test stand. Measured the TDC sensor output at 1.33 volts AC and the Crank sensor at 3.96 volts AC. I think my problem is somewhere else.

Looks like ecu time like you said before.Only thing left is to see if that signal is going to the ecu and the signal coming out.I can look up the wire colors tonight if you want.And no I do not know of any place that sells reman ecu,s.Maybe someone else will log in with that info.Carl

Looks like ecu time like you said before.Only thing left is to see if that signal is going to the ecu and the signal coming out.I can look up the wire colors tonight if you want.And no I do not know of any place that sells reman ecu,s.Maybe someone else will log in with that info.Carl


If the dude is getting error codes, that means his ECU is functioning. I think you need to get your shit straight before you blame the ECU.

Made another test to determine if there was a pulsating voltage source from the ECU to the Igniter.

With an oscilloscope attached to the connecting white wire, and the engine spinning, a constant positive 10.5 volts was observed. There was no cyclic voltage drop to trigger the igniter. Same test with no connection from the ECU to the igniter gave the same results.

Is a good igniter, connected to the ECU, required to see the pulsating output of a properly functioning ECU on an oscilloscope?

Hog Caller,Check your pm.Carl

just wondering if anybody figured out what this problem was im havin the same problem with my 91 integra ls 5spd i replaced distributor, spark plugs n wires throwin a code 15 still
much appreciated