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Fuel Injection ECU codes/ rough idle and slow throttle respo
Greetings all. My brother just bought an a 86 ASPY with the preverbial erratic idle and slow throttle response at lower RPM's. I am trying to resolve a problem for him. The computer indicates a bad TPS with W steady and 0 + 1 flashing. The FUEL SYSTEM light is ON STEADY . I have read many forum subject post regarding this matter and still cant seem to isolate the cause after throwing many parts and hours at the problem. I am seeking wisdom, guidance and experience from you wingers out there who have been down this same road. This is a long post so bear with me.


TPS sensor replaced with a used sensor that checked to specs. Reference voltage and return Voltages back to the computer were good. Smooth resistance operation and voltage increase/decrease were smooth and within specs. 3 pin connector male and female replaced. DISCONNECTED TPS 3 PIN CONNECTOR AND STILL GET SAME ECU CODE

pbl/pbr swapped with each other and a pair of used ones that I purchased. Vaccum lines to the sensors were replaced.

gl/gr replaced with a new set

NS sensor replaced with NEW / Modified from 85 LTD

ECU SWAPPED: Both ECU's display the same code when the ignition is FIRST switched to ON. Engine NOT Running.



Cone filter cleaned at fuel pump inlet.

Previous owner had the throttle bodies sync'ed, Modified TPS installed ( I replaced with a used one ) fuel filter replaced, New orings for injector 1, cleaned and tested all injectors, greased all electrical connections on injection harness , compression checked the bike, all GOOD, replaced all exhaust gaskets.

I suspect an electrical signal problem somewhere in the injection harness as I get the code on both ECU's when the key is first turned on but not sure where to go from here. If the bike were running and pressures and flows were involved with the code displayed I obviously would have more to troubleshoot. Talk to me Honda SEI experts!
#1 01-08-2012, 04:39 PM,
if you "greased" all the electrical connections i would try removing it,clean connections are what you need,greasing may be preventing system from properly working,imho
1987 Aspencade 129K
1986 SEI 93K
2014 Tri-Glide HD 17K

#2 01-08-2012, 08:27 PM,
Have you resolved the issue yet? I see that you are getting lot's of help on another "wing" forum.
'96 ST1100
Brewerton, NY
#3 01-10-2012, 02:52 PM,
]As an update. Bike was not purchased off of Craigslist! Not much time to work on the wing lately. I still have the problem. I jumpered the 3 TPS wires from the 3 pin connector to their respective positions 3,11 and 29 on the ECU connector. This did not remedy the L.E.Ds indicating a positions sensor malfunction. Zero is steady with 1 and 2 flashing. Fuel System light is on continuously when the switch is on as well. Bike runs but throttle response is slow and idle erratic. I have used the SEI supplement and the TPS sensor test good and all values are correct. HERE'S THE PUZZLE FOR ME:

The fuel system light is powered from pin 14 on the ECU and as I mentioned it is on continuously with the switch. When I check the voltage comming out of pin 14 the value is 1.44 to 1.46 volts. Assuming the light is a 12volt lamp, how can pin 14 illuminte the light with only 1.44 volts? Again, assuming that 1.44 volts IS NOT powering the light, where is the voltge comming from that makes it light? That being said, I am now looking for a rogue voltage source that is powering the light and feeding back onto pin 14 causing all my grief. Any input is greatly appreciated. Thanks folks!
#4 01-25-2012, 04:52 PM,
When I sold my LTD, all of the manuals went with it. Sorry I cannot help with the pin / wire numbers, colors, etc. I am a medium duty diesel electronics and engine guy. What you have going on, is what we call "the freak of the week". It seems like everything has been covered, but yet the problem still exists. Pulling your hair out yet? :d It appears that you have all of the technical diagnostics covered thoroughly. Some of these things you may have all ready looked at, but let's take a step back and review the most common electronic problems. Take a look at the following:

Fully charged and healthy battery? A shorted or a low cell can cause electronic problems.
" ALL" positive power points been checked for corrosion and tightness?
" ALL" grounds are clean and tight? The LTD and SEI have ground points all over the bike. They all need to be good. ECM power and grounds?
Have you looked at the fuses and fuse block? Corroded / loose terminals?
Have you checked the relays and relay blocks for corroded or loose terminals. Have you switched the relays around to see if you have a bad one?
This thing is now 26 years old. Things are getting crusty....

When I had my LTD, I saw some potential ground problems. Most things were grounded to the frame at any given point. At any major ground point, I added a ground strap and ran it to the battery ground cable. This way, as a preventive thing, I knew I wouldn't be relying on the frame as a sole ground.

I hope this helps. Please report back with any findings. It's gotta be something simple.... You just gotta find it.... Tongue
'96 ST1100
Brewerton, NY
#5 01-26-2012, 08:45 AM,
Thanks for the reply. I have checked all of the connectors on the FI harness for corrosion and they have been separated and blasted with contact cleaner and reassembled with diaelectric grease. I have ran 2 additional ground straps from the negative battery post, one to the frame and one to the engine when I first started working on the bike. I have not switched relays 4 and 5 but thanks to your reply I will do that when I get home. The battery is less than 1 year old and it's a super dooper battery of some sort that the previous owner bought before my brother got the bike. I will take down to the parts store and let them test it for me even though it maintains a good charge. I honestly believe that I have an open or bad ground (corroded) somewhere in the circut. And YES, I am pulling my last hair out on this one. Imput from a member on another forum suggested that the ECU may not be getting a good ground so I'll be ringing all of the gnd circuts on the ECU too! Thanks again for your imput. I will solve this one way or the other!
#6 01-26-2012, 09:50 AM,
Firstly, I apologize for my english ^Smile^
cal757 Wrote:]...Assuming the light is a 12volt lamp, how can pin 14 illuminte the light with only 1.44 volts? ...
You must look at electric diagram.
Indicator-bulb (Fuel-Sys) has 12V (+) from battery and PIN 14 from ECU switch on ground signal to bulb.

You must check:
- all connections betwen TPS sensor couplers and ECU for loose contacted with ohmmeter.
- sensor resistance
- sensor input voltage
- sensor output voltage
All You needs is LIFE...
#7 01-26-2012, 10:55 AM,
I also forgot to mention the "wiggle test". You won't find this test procedure anywhere else but the trucking industry. Although it is still a valid test for anything electronic.

You keep mentioning the fuel injection harness, but have you also looked at the main wiring harness and all the sub-harnesses? Remember that there's alot of power and ground circuits in there, most inner connected / tapped in together.

Physically grab a hold of all of the harnesses at point "a" and work your way to point "b". Wiggle, bend, pull, shake, push and check for any difference. Remember that the only way to see if you've corrected a hard / active fault and re-set the ECM, is to turn off the ignition and re-start.

Look at the bright side....At least you have an active fault.... It could be intermittent ! :d
'96 ST1100
Brewerton, NY
#8 01-26-2012, 12:35 PM,
I have checked the input and output voltages as well as the resistance multiple times and all are spot on or within tolerance. I have checked all of the connections that I could easily reach on the other harnesses and ALL on the FI harness. Your points are right on because this issue is going to be somewhere that I have not looked or something I have not touched. There will be an exorcism of this gremlin eventually rest assured, and thank you again Wingers for your support!
#9 01-26-2012, 04:09 PM,
UPDATE: I think that I have resolved the fuel system light issue being alway's on. I powered pin 30 of the ECU connector with 12vdc directly from the battery and the light went out. It re-appeared on steady again after depowering/repowering the system and I again bypassed the harness wiring applying 12vdc. The light went out and remained out on numerous subsequent power ups. The power to pin 30 is from the engine stop switch. The starter relay is powered from the same circuit. My theory is that the relay has a bad contact or corrosion that provides the rogue voltage or ground that the light needs to power on. Anyway, knock knock it appears NOT to be connected to my throttle sensor issue. RIDDLE ME THIS FELLOW WINGERS: I HAVE A DIRECT SHORT ON PIN 29 OF THE ECU CONNECTOR WHEN IT IS PLUGGED INTO THE COMPUTER. I ALSO HAVE 5 VDC REFERENCE POWER ON THAT SAME PIN AS IT SHOULD BE.
Is this correct? IF NOT, what is the remedy? Normally, pin 3 is the ground for the throttle sensor. Two ECU's, same result! Please chime in and thanks again for your imput.
#10 01-29-2012, 08:00 AM,
ALSO: With the throttle sensor completely removed off of the wing, I still get the same code on the ECU, W steady 0 and 1 flashing which would indicitave of a Throttle sensor OPEN or SHORT. With the sensor off of the bike it surely must be harness problem. I have checked for shorts and opens 6 ways to Sunday and I am still missing the boat on this Throttle sensor issue. I just now finished checking the reference voltage, return signal voltage FROM the sensor to the connector and resistance values and ALL are at specifications. Chime in folks and thanks!
#11 01-29-2012, 08:54 AM,
UPDATE Now, My fuel system light does not come on for 2 seconds when I turn on the swictch now and before I bypassed the connections to force power to it, I could not turn it off. I have went from one extreme to the other when it comes to the Fuel System Light. The bike seems to be idling much better but I still have the codes and the fuel system light does not power on and off with the switch now. Man at the gremlins plagueing me on this one.
#12 01-29-2012, 12:27 PM,
You are getting distracted with all of these things popping up at the same time. Your bouncing around from problem to problem. Stay focused.... Slow down...You'll work faster.... :d

It sounds like your getting warmer with manipulating power and ground to the ECM. Stay there. Everything revolves around the ECM getting full power and ground. Don't worry about the TPS right now.

The ECM is getting better power and ground with the bypasses. That's why it's running better. Have you yet gone through ALL of the grounds and ALL of the power sources like I suggested earlier? Fix the ECM power and ground problem FIRST. Then things will start pulling together. Go through the manual and look at everything that powers and grounds the ECM. Even the things that may be "sharing" those power and grounds.
'96 ST1100
Brewerton, NY
#13 01-29-2012, 01:22 PM,
As you can see I am playing out this scenario on both Steve Saunders site as well as this one hoping to garner more input. The Fuel system light is OFF and the ECU still indicates a TPS fault. In answer to the query regarding the grounds, I did check the ECU at pins 16,34,2 and 20 and all have continuity with the battery ground. Even though the bike is idling better its burning rich to the point where my eyes burn. I remember reading that richness could be a symptom of a faulty PB sensor so with the bike running I disconnected the PB sensors one at a time and when I disconnected PBL, the bike stopped! Using a pair of spare PB sensors that I have, I replaced PBL with the spares and repeated the process. Both times after disconnecting PBL the bike stopped. PBR must be bad or the PBR circuit bad if I understand the process of elimination correctly. This may be totally unrelated to the TPS problem. I left it there and called it a day so as soon as I complete this reply I will resume working on the bike. I think that I am getting there but it's one step forward and 2 steps back seemingly. Stay tuned and I'll report later my findings. Thanks again!
#14 01-30-2012, 05:38 AM,
Ok... I will yield to the Steve Saunders site. Best wishes in troubleshooting and repairing your bike. ~O)
'96 ST1100
Brewerton, NY
#15 01-30-2012, 03:53 PM,

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