86-Gl1200-SEi, sensor failure detected but, test OK?

[KennyRic]

I've got a 1986 gl1200 SEi -(fuel injected model), as a non running project. It cut-out and died ~3 years ago while the previous owner was riding, all he new of the problem was that it didn't have spark after that. When I got into troubleshooting the bike, I found that there was no power to supply the CFI relay-to-ECU circuit. I Found that the 2nd 30amp dog-bone fuse had a break in it (from age and oxidation, I assume this went bad after the sitting a few years not running do to the way the owner described the original symptoms). After fixing the fuse problem the ECU now had power, now after trying to start the bike the ECU trouble lights came on. The lights indicated a GL Sensor (one of the two sensors on the camshaft end) fault, and a NS Sensor(crankshaft pulse generator) fault. I performed the test procedures for these sensors found in the LTD and SEi supplement manual, checking resistance at the ECU connector. The cam sensors were in spec at 10 Ohms below the upper limit, and the crank sensor tested in the right range too. I plugged the connector back into the ECU and cranked the engine with a little throttle and it started, yet the trouble light patterns were still blinking on the ECU, the manual states that when the NS sensor fault is present the fuel injection and spark are stopped, yet it was running while indicating that those faults. I haven't been able to run it long enough to see if the engine quits once its warm, as is common when the crankshaft pulse generator is going bad. However most of the time it doesn't start when I try it.
Can anybody give me any input on how the ECU always says there's a fault with those sensors yet they test ok by the manuals specs?
And also what should I do when the sensors test ok and the wiring is fine?, replace them and hope for the best?
Thanks in advance for the help, feel free to give any other helpful input for my problem.

[KennyRic]

As an update to my situation, recently iv been able to get the bike to start when ever I try, and now it’s only indicated the the Ns sensor fault once, normally when it starts it will keep flashing that Ns sensor failure pattern. I also let the engine run until it was warm, sense the weakness of the Ns sensor/pulse generator is said to show most commonly once it’s warm. But the engine never stalled even when the belt covers were warm. The Gl sensor fault is still persistent though.

[Rednaxs60]

Have been watching your thread, have the '85 Limited Edition. I find the slot in the frame to view the ECU error codes when the ECU is installed under the rear trunk makes it hard to properly see the error codes. I have read where some have enlarged this slot to better view any error codes. You could also remove the ECU from under the rear trunk to view the error codes as well.

The engine will not start if there is an Ns sensor fault. If it does there is not an Ns sensor fault.

The Gr/Gl sensors are an interesting in that these are Honda's way of simulating sequential, key word is simulating, firing of the injectors, and getting a faster start of the engine. The CFI system will operate correctly on one "G" sensor, and as you mention, the Gl sensor appears to be faulty. The fellows on the CX500 forum have a work around to this and use an LX579 sensor in place of the original since the original is no longer available. Have to modify the Gr/Gl plate to accommodate.

Good luck

[KennyRic]

It makes no sense for it to run while displaying the Ns code, but I have a video (that I don't know how to share) of it doing that, the Ns sensor code has been there inconsistently, but the Gl sensor code is always there. I'm starting to think that when its not starting once and a while it may be just that the battery is to weak to spark? ,and maybe a weak battery causes imperfect sensor readings to the ECU also?

[Rednaxs60]

It makes no sense for it to run while displaying the Ns code, but I have a video (that I don't know how to share) of it doing that, the Ns sensor code has been there inconsistently, but the Gl sensor code is always there. I'm starting to think that when its not starting once and a while it may be just that the battery is to weak to spark? ,and maybe a weak battery causes imperfect sensor readings to the ECU also?

This is a mystery.

Have the battery load tested and determine if it needs to be replaced, or not. The battery only has three purposes, start the engine, absorb electrical system voltage spikes, and supplement the electrical system power requirements when the stator is not turning fast enough to provide all the power the system requires, nothing more - nothing less. Does not impact on the operation of the sensors.

I would check the Gr/Gl sensor connection under the shelter. Disconnect and make sure everything is making a good pin connection, the same with the Ns sensor. These are located under the shelter. These wires do get bent quite a bit and there might just be enough to keep the engine going, but also indicate a sensor fault. Check theses sensors are in spec at these connections too.

Good luck.

[Rambozo]

If the battery can spin it over, it has more than enough power for it running.
Since Honda doesn't publish much in the way of what triggers a fault code in the various sensors, it would be difficult to know if a sensor is just out of spec enough to trigger a fault, but not enough that it won't run.
Of course if the ECU says a sensor is bad when it's not, there is a problem with the ECU.

[KennyRic]

It seams a new battery fixed the confusing ECU code problems, after fixing up all the little things I got into testing it out. 200 miles later and the stator went out, iv now got a rick’s stator installed in the engine. I’m now reinstalling the engine BUT, I can’t confidently determine where the small hose that comes off the timing inspection cap
(only on 86Sei’s?)needs to go.I’m thinking it must go to this sensor but I don’t know what it’s purpose would be, the sensor or actuator threaded into the top right rear of the engine -it’s the only part with a braided metal liner on the wiring for it and it has a vacuum line sized port. Does anybody have any answers to that problem

[Rednaxs60]

It seams a new battery fixed the confusing ECU code problems, after fixing up all the little things I got into testing it out. 200 miles later and the stator went out, iv now got a rick’s stator installed in the engine. I’m now reinstalling the engine BUT, I can’t confidently determine where the small hose that comes off the timing inspection cap
(only on 86Sei’s?)needs to go.I’m thinking it must go to this sensor but I don’t know what it’s purpose would be, the sensor or actuator threaded into the top right rear of the engine -it’s the only part with a braided metal liner on the wiring for it and it has a vacuum line sized port. Does anybody have any answers to that problem

The small hose goes from the timing mark cap to the oil pressure sensor on the right side of the engine that you mention.