Check Engine Light and battery condition

[NoVa Chris]

Revised posting: I started this thread in the belief that a bad battery was causing my MIL (check engine light) to come on occasionally. Replacing the battery seemed to solve the problem, briefly, but then the problem returned and I began experiencing running problems (cutting out at higher speeds.) If you read through this thread, you'll see that I considered that perhaps the fuel injection system was going into a "limp mode" and was preparing to chase down an FI problem. Before doing so, however, I replaced the spark plug caps, and it turns out that a bad cap may have been the culprit all along. With new NGK caps, both the MIL and the poor running problems seemed to have cleared up. (I am not entirely clear why bad caps would trigger the MIL, but the caps seem to be the cause of my problems with running at higher RPMs.) Posts in this thread from other forum members have good information on reading MIL codes and other useful comments. But I caution anyone reading this thread that my own theories as I tried fixing this problem on my own (bad battery, FI problem) may have been red herrings.

(From initial post) My check engine light was coming on occasionally, no other problem with the NT. Sometimes it stayed on after starting (rather than going off within about 3 seconds), sometimes it came on during highway riding and stayed on. Then it might stay off for a week or more.

I ran voltage checks on the battery. Even after reaching a "green" indicator on a battery tender, the battery voltage (engine off) was below spec. Good voltage with engine on, so I concluded the charging system was OK.

I installed a new battery a couple of week ago and have had no check engine light problems since then.

By the way, in the NT the battery is laid on its side. This shouldn't be an issue as the battery is sealed. But the NT battery connections fit on the battery terminals from the side rather than over the top. I had to hacksaw off about 1/16 of an inch from the NT's positive battery lead to get it to fit the aftermarket battery I bought. No real problem with this, just a minor adjustment.

 

[dnktng]

Check Engine Light and battery condition

...and possibly battery connection conditions.
My only experience with a MIL happened couple of months ago. I would get intermittent MIL's after turning the ignition switch on. Sometimes the MIL would remain after starting, sometimes it would clear. Also if the MIL came on turning the ignition switch on, it may clear by turning it off & back on without starting the engine. Read the blink code at MIL if it stayed on and it was a 1, MAP sensor low or high volts. Also checked the stored codes and the only code was a 1. Troubleshooting guide in section 6 of the service manual says to inspect the MAP sensor connector, and ECM connectors (2). I choose to disconnect, inspect & reconnect the ECM connectors first since this requires less dis-assembly than the MAP sensor (I'll do that within a couple of months when checking valves). Also disconnected, cleaned, reconnected the battery connections. Even though the manual didn't say to check the battery or battery connections it seems like the right thing to check because 1) MIL 1 is a voltage issue 2) needed to disconnect ECM connectors......probably good idea to disconnect battery first anyway, at least it doesn't hurt. 3) Battery connections are always problems due to corrosion, stacked connectors from add-on circuits (fuzeblock, etc), high relative amperage, 4) easy to check, & 5) battery is 3 year old original equipment.

Reconnected everything, cleared DTC codes, and haven't had a MIL since. No MIL's codes now....so, just continuing to monitor.

There isn't any harm in checking the battery & connectors when MIL codes start coming in, but I'm not smart enough to know if it could be the cause of the MIL's.

 

[NoVa Chris]

So now I am not sure the battery was the cause of my MIL problems after all. Yesterday when I started a run I had a flashing MIL -- eight flashes which I think indicates TPS voltage issue -- but then on a second start it stayed off and everthing seemed fine. (Before I changed the battery, I was not getting flashing MILs, just steady ones.) Then running at about 60 MPH my NT suddenly lost power, and the MIL came on steady. As RPM's dropped and I closed the throttle, the engine regained power, but it would stall when I tried to run it back. As long as I stayed below about 40 things were OK. Low RPM and idling seemed unaffected.

If I understand the Honda manual correctly, the FI has a fall back map that allows the engine to continue to run if some faults are detected, but only at lower RPMs, so you can limp home. I presume that's what happened to me. Phil T and Handsome Prince have reported experiencing a similar situation, including the eight flashes and loss of power. Without a warranty or a local service department that I trust, I am trying to chase this down myself.

 

[Phil Tarman]

Chris, That's what mine did. They said the eight flashes indicated low voltage at the TPS. They changed the regulator/rectifier and I haven't had any more problems in about 65-70,000 miles.

 

[NoVa Chris]

Phil, you're an inspiration to NT owners everywhere. Based on your previous posts, I went ahead and ordered the reg/rectifier. I have my fingers crossed, and I'll post the results once I try it out.

My running problem on the NT occurred the day after I sold my VStrom 650, which in the years I had her never ever gave me a problem.

 

[Phil Tarman]

Chris, I sure hope that the regulator/rectifier fixes your problem! My "inspirational value," such as it is, sure doesn't give me extra mechanical/electrical wisdom.

But if it's the throttle position indicator, I'm not sure you can even buy that without buying whole the throttle body assembly.

 

[Rmcapozzi]

Chris,
What you are describing is exactly what I'm running into now with my wife's NT. The MIL code of 8 (8 flashes) is unfortunately only the main code which is either a low OR high voltage reading at the TPS. You need a code reader plugged into the diagnostic port to get the sub-code (a 1 or 2) which will specify if the voltage reading is high or low.

It is an intermittent problem we are having and turning the bike off and back on seems to reset the problem (temporarily). When the system senses a problem I believe it goes into the "safe" mode which is basically an idle so while at speed, it feels like a total loss of engine power (which it is) but the motor doesn't actually shut off.

I am a bit skeptical that the rectifier/regulator has anything to do with the problem that I'm experiencing associated with the MIL 8 code as the trouble shooting path in the manual points to 3 possible issues.
1) problem with the wiring harness (broken connector/wire)
2) a bad TPS
3) a bad ECM

The sub-code dictates the path you head down to diagnose the issue but the above three are the only "resolutions" identified.

There are a myriad of other sensors on the bike that will throw a low/high voltage warning as well, so if it was a problem with the regulator/rectifier, why only the TPS and not the other sensors? The MIL can present multiple codes. For my situation, we only ever get an '8'.

My experience with bad regulator/rectifiers is fried batteries (or connectors) from over charging or dead batteries from under charging.

I'm taking the bike to Blue Ridge Powersports in Harrisonburg, VA this Saturday to have them look at and hopefully fix it under warranty. My money is on the TPS which requires replacement of the entire throttle body for a healthy chunk of change (glad I have the warranty).

I'll let you know what I find out. Keep us posted on your progress. I hope you are successful in solving it.

So now I am not sure the battery was the cause of my MIL problems after all. Yesterday when I started a run I had a flashing MIL -- eight flashes which I think indicates TPS voltage issue -- but then on a second start it stayed off and everthing seemed fine. (Before I changed the battery, I was not getting flashing MILs, just steady ones.) Then running at about 60 MPH my NT suddenly lost power, and the MIL came on steady. As RPM's dropped and I closed the throttle, the engine regained power, but it would stall when I tried to run it back. As long as I stayed below about 40 things were OK. Low RPM and idling seemed unaffected.

If I understand the Honda manual correctly, the FI has a fall back map that allows the engine to continue to run if some faults are detected, but only at lower RPMs, so you can limp home. I presume that's what happened to me. Phil T and Handsome Prince have reported experiencing a similar situation, including the eight flashes and loss of power. Without a warranty or a local service department that I trust, I am trying to chase this down myself.

 

[NoVa Chris]

Very helpful that you're sharing your experience. I am trying to fix this on the cheap and without getting into heavy diagnostics. Did I mention I used to be a VW mechanic? Aircooled, that is. Which may explain my reluctance to dive in deep end of the MIL world, but also unwillingness to "give up" and take it to the dealer. So as of today, I am still waiting for the rec/reg I ordered. I absolutely agree with you that this does not seem to be the problem, but based on Phil's experience and my sense that uneven voltage can trigger some problems, I think its worth a gamble. While waiting, I removed air cleaner and looked at hose routing and wiggled connectors. Nothing out of whack. Put everything back together and voila, problems cured. For a week or so. Today, since my employer has closed its doors, I decided to take a longer ride, and on the freeway, MIL comes on again steady, but running is still OK. Pull off, shut bike down and restart, MIL off. But I decide to return home, and once back up to speed, the bike started cutting out again. No MIL light but intermittent cutting out esp at higher RPMs. Idle still OK. Nursed home, and now I am looking at the spark plug caps (again thanks to this site for flagging this problem) since suddenly it does sound more like a hot engine/higher RPM problem, which certainly could be a spark plug cap issue. I will try new caps and see if it helps before installing the new rec/reg. Please do post the results of your experience with Honda. Chris

 

[dnktng]

Chris, Have you read the stored codes in ECM from this latest ride? That info would be helpful. Everytime you're getting a MIL and it clears, there is a code stored in the ECM. The codes can be read using the procedure on 6-16. The special tool it describes is not really needed, just need a small wire to short the Brown & Green/White wire connections of the DLC plug. This shorting wire is shown installed on the diagram on page 6-8. Also, after all the codes are read you can clear out the codes using the shorting wire and the procedure on page 6-16. Then if your NT acts up again when at high speed you could later read the MIL code even though you were unable to see it when riding. If you don't clear the codes, the new codes could just be one of many stored in the ECM and not be as much help for further troubleshooting.

Tend to agree that the Reg/Rectifier is unlikely fault, but rectifiers can fail and cause an unsmooth DC that may be causing voltage spikes that may (it's a stretch) cause your MIL to come on. Hate to see you spend money on a battery & reg/rectifier and it's not the fault. Troubleshoot more, spend less.

Can't emphasize this enough. Even the service manual mentions it..." A faulty PGM-FI system is often related to poorly connected or corroded connectors. Check those connections before proceeding." You mention you wiggled some connectors. Seriously, disconnect the connectors to your TPS (and any other sensor that has given you a MIL code) and the 2 multi-pin ECM connectors, inspect the connections, clean the connectors if needed with isopropyl alcohol, and reconnect. It's FREE!, and often the cause of intermittent MIL's. And it's FREE!

Keep in mind that your TPS is nothing but a cheap potentiometer. It's a mechanical device that can possibly get dirty. The TPS is not sold separately from the throttle body. Some UK NT700 owners have reported some luck cleaning it with WD40. I'm not overly excited about that particular spray on electrical components, but some electrical cleaner may help (isopropyl alcohol or air). This may be difficult because of it's location. IIRC, it's buried tightly in the throttle body. Being a cheap potentiometer, simply exercising may help....by opening & closing the throttle gently several times with the engine off. No guarantees on this advice, but it wont hurt anything, & it's FREE!
Good Luck.

 

[seagrass]

Chris, Have you read the stored codes in ECM from this latest ride? That info would be helpful. Everytime you're getting a MIL and it clears, there is a code stored in the ECM. The codes can be read using the procedure on 6-16. The special tool it describes is not really needed, just need a small wire to short the Brown & Green/White wire connections of the DLC plug. This shorting wire is shown installed on the diagram on page 6-8. Also, after all the codes are read you can clear out the codes using the shorting wire and the procedure on page 6-16. Then if your NT acts up again when at high speed you could later read the MIL code even though you were unable to see it when riding. If you don't clear the codes, the new codes could just be one of many stored in the ECM and not be as much help for further troubleshooting.

Tend to agree that the Reg/Rectifier is unlikely fault, but rectifiers can fail and cause an unsmooth DC that may be causing voltage spikes that may (it's a stretch) cause your MIL to come on. Hate to see you spend money on a battery & reg/rectifier and it's not the fault. Troubleshoot more, spend less.

Can't emphasize this enough. Even the service manual mentions it..." A faulty PGM-FI system is often related to poorly connected or corroded connectors. Check those connections before proceeding." You mention you wiggled some connectors. Seriously, disconnect the connectors to your TPS (and any other sensor that has given you a MIL code) and the 2 multi-pin ECM connectors, inspect the connections, clean the connectors if needed with isopropyl alcohol, and reconnect. It's FREE!, and often the cause of intermittent MIL's. And it's FREE!

Keep in mind that your TPS is nothing but a cheap potentiometer. It's a mechanical device that can possibly get dirty. The TPS is not sold separately from the throttle body. Some UK NT700 owners have reported some luck cleaning it with WD40. I'm not overly excited about that particular spray on electrical components, but some electrical cleaner may help (isopropyl alcohol or air). This may be difficult because of it's location. IIRC, it's buried tightly in the throttle body. Being a cheap potentiometer, simply exercising may help....by opening & closing the throttle gently several times with the engine off. No guarantees on this advice, but it wont hurt anything, & it's FREE!
Good Luck.

All very sound advice. I know of a member on this site that has had their bike off the road for many months trying to resolve a problem that is pointing to an electrical fault. The dealer has even replaced the wiring loom but the problem persists. I suspect it is a connection issue of some sort but that is just my thoughts.

 

[Rmcapozzi]

Chris, Have you read the stored codes in ECM from this latest ride? That info would be helpful. Everytime you're getting a MIL and it clears, there is a code stored in the ECM. The codes can be read using the procedure on 6-16. The special tool it describes is not really needed, just need a small wire to short the Brown & Green/White wire connections of the DLC plug. This shorting wire is shown installed on the diagram on page 6-8. Also, after all the codes are read you can clear out the codes using the shorting wire and the procedure on page 6-16. Then if your NT acts up again when at high speed you could later read the MIL code even though you were unable to see it when riding. If you don't clear the codes, the new codes could just be one of many stored in the ECM and not be as much help for further troubleshooting.

Tend to agree that the Reg/Rectifier is unlikely fault, but rectifiers can fail and cause an unsmooth DC that may be causing voltage spikes that may (it's a stretch) cause your MIL to come on. Hate to see you spend money on a battery & reg/rectifier and it's not the fault. Troubleshoot more, spend less.

Can't emphasize this enough. Even the service manual mentions it..." A faulty PGM-FI system is often related to poorly connected or corroded connectors. Check those connections before proceeding." You mention you wiggled some connectors. Seriously, disconnect the connectors to your TPS (and any other sensor that has given you a MIL code) and the 2 multi-pin ECM connectors, inspect the connections, clean the connectors if needed with isopropyl alcohol, and reconnect. It's FREE!, and often the cause of intermittent MIL's. And it's FREE!

Keep in mind that your TPS is nothing but a cheap potentiometer. It's a mechanical device that can possibly get dirty. The TPS is not sold separately from the throttle body. Some UK NT700 owners have reported some luck cleaning it with WD40. I'm not overly excited about that particular spray on electrical components, but some electrical cleaner may help (isopropyl alcohol or air). This may be difficult because of it's location. IIRC, it's buried tightly in the throttle body. Being a cheap potentiometer, simply exercising may help....by opening & closing the throttle gently several times with the engine off. No guarantees on this advice, but it wont hurt anything, & it's FREE!
Good Luck.

And if the bike's "check engine light" is on, if you simply keep the bike running, come to a stop and place the bike in neutral, the engine light will blink the MIL code. No special tool or shorting of the diag connector is needed.

Just count the number of times the light flashes. After a short pause the code will report OR the NEXT code (if multiple MILs exist) will flash, the MIL code flashing is repeated until the bike is turned off or the bike is taken out of neutral.

 

[NoVa Chris]

Thanks to everyone who offered advice on the MIL codes, double checking connections, etc. I now think that bad spark plug caps may be the cause of my NT cutting out at higher RPMS. I did not bother with Honda and warranty, I just got a pair of NGK angled resistor caps (VDO5F), from my dealer, for about $6 each. I was able to change the caps by removing the black plastic mid-cowls. The NGK's are not exactly the same angle as the OEM caps, but they fit perfectly. In several longer runs since changing the caps, I have experienced no running problems, and no MILs. I'll post updates if the problem returns.

 

[Rmcapozzi]

Thanks to everyone who offered advice on the MIL codes, double checking connections, etc. I now think that bad spark plug caps may be the cause of my NT cutting out at higher RPMS. I did not bother with Honda and warranty, I just got a pair of NGK angled resistor caps (VDO5F), from my dealer, for about $6 each. I was able to change the caps by removing the black plastic mid-cowls. The NGK's are not exactly the same angle as the OEM caps, but they fit perfectly. In several longer runs since changing the caps, I have experienced no running problems, and no MILs. I'll post updates if the problem returns.

Thanks for the update, Chris. Replacing the plug caps on our NT didn't change a thing...other than now having the updated plug caps. Once we have it figured out, I'll post the solution for our issue.