I have a 2005 FLSTFI with Stage 1 + SERT.

I recently took it to the dealer to fix my broken fuel gauge; they said the sending unit had come loose inside the tank. I then went on a 200 mile ride with my club, during which it poured and we were riding primarily on muddy clay roads. After returning home, I power sprayed it at the car wash to get rid of all the dried red clay that was imbedded everywhere. A couple days later my check engine light started coming on occasionally, maybe for 4 or 5 seconds, then it would go out. I also noticed that I was experiencing minor idle hang. This may not be the right term for it, but let's say I was in 4th gear at 55mph. Normally closing the throttle causes standard engine braking, with lots of popping coming from my bigshot longs. But now, instead of moderate engine braking, it slows only slightly with a higher idle until I pull in the clutch or it hits about 40 mph and drops to standard idle. This doesn't happen every time, but most of the time after hitting higher RPMs.

I pulled the DTCs and they all seem to point to my voltage regulator:
P0563 Battery Voltage High EFI
B0563 Battery Voltage High TSM/TSSM
B1006 Accessory Line Overvoltage Instruments
B1007 Ignition Line Overvoltage Instruments

I've checked for loose grounds, standard stuff, and I will be doing more thorough testing to rule out the stator this weekend. What I don't understand is how a bad voltage regulator or stator could be affecting my idle speed like that. I've noticed that the check engine light always comes on AFTER the idle speed drops back to normal. Could it be affecting my throttle position sensor perhaps? Any ideas?

 

Last night I followed the steps in the H-D Electrical Diagnostics Manual and determined that the stator is good, which leaves the voltage regulator as suspect. The odd part is, aside from the DTC codes, I can't find anything wrong with it. I tested the voltage across the battery terminals with the engine running at idle and it reads 13.3v. It climbs normally as I rev the engine, but stayed well under 15v, which is within spec according to the manual. Stator and AC check out OK. I don't have a load tester so I can't truly rule out the voltage regulator, and will probably order a new regulator anyway, but that brings me back to the actual problem. Why is this affecting my idle speed upon deceleration? And why does the light come on after the idle speed drops to normal?

 

I'm thinking you pressure washed dirt into the wrong place, possibly binding the trottle body. High pressure should not be used to clean a bike. Water and dirt can get forced into many places you don't want it. If you check the regulator output with everything powered up (all accessories) and it reads normal, that is a valid load test.

 

I agree with you, but sometimes there's not many other options. This was some serious muck. This thought had crossed my mind too, which is why I mentioned it in the original post.

During troubleshooting last night I did remove the air cleaner and inspect the TP sensor, throttle wheel, throttle and idle cables, most of the stuff in that area, everything appeared to be operating normally. I'm not certain that would throw the DTC codes that I'm seeing, it really seems to be electrical.

One of my coworkers thinks that if the regulator isn't working properly, and is sending higher than normal voltage to the battery and ignition lines, it's possibly sending higher than normal voltage to the injectors as well, which he thinks is affecting the idle speed.

My next plan is to rig up my ammeter so I can actually watch the voltage as I'm riding. If the ECM is seeing voltage >16v for more than 5 or 10 seconds, which is what it takes to register the B1006 and B1007 codes, I should be able to see it on the meter as it's happening. Hopefully it's just a faulty regulator.

 

I replaced my voltage regulator today and everything is back to normal. So I guess to answer my own question, yes, a bad voltage regulator can indeed cause idle hang.