Brief "limp" mode while accelerating
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Joined: Jan 2021
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From: Texas
Brief "limp" mode while accelerating
Hello. One week ago I got my very first Harley - 2016 Fat Boy FLSTF (103). It had less than 1K miles.
Perhaps from sever underuse, it got an issue.
When I accelerate, sometimes the Oil light briefly flashes and immediately goes off, Check Engine turns on; then a few seconds later goes off. During that time the engine goes into "limp" mode. It loses all power.
That becomes a dangerous experience when riding on a highway.
So far, I've got several hypothesis, none of which helped though.
- I checked the engine oil. While in hot, it was a 1/4 inch below max. So I added a bit more oil. That did not help.
- I checked Spark plugs. One of them had 0.043 gap. I fixed it for 0.039. That did not help.
Now my theory is that either Oil Pressure Switch or its wire is faulty. After researching the wiring diagram, it looks like the Oil icon turns on when the oil pressure becomes low and the wire effectively gets grounded thus enabling the circuit. Here is what I am planning to try:
1. Disconnect the wire from the Oil Pressure switch and run the bike. If the problem is gone, then the issue must be within the Oil Pressure Switch. Need to be replaced. Otherwise, proceed with the step 2.
2. Disconnect wire from BCM module connection. If the problem is gone, then the issue is with the wire between the Switch and BCM. Wire needs to be replaced.
So my question is - if I run the bike with the Oil Pressure Switch wire disconnected for a short period of time, can it cause any issue?
Perhaps from sever underuse, it got an issue.
When I accelerate, sometimes the Oil light briefly flashes and immediately goes off, Check Engine turns on; then a few seconds later goes off. During that time the engine goes into "limp" mode. It loses all power.
That becomes a dangerous experience when riding on a highway.
So far, I've got several hypothesis, none of which helped though.
- I checked the engine oil. While in hot, it was a 1/4 inch below max. So I added a bit more oil. That did not help.
- I checked Spark plugs. One of them had 0.043 gap. I fixed it for 0.039. That did not help.
Now my theory is that either Oil Pressure Switch or its wire is faulty. After researching the wiring diagram, it looks like the Oil icon turns on when the oil pressure becomes low and the wire effectively gets grounded thus enabling the circuit. Here is what I am planning to try:
1. Disconnect the wire from the Oil Pressure switch and run the bike. If the problem is gone, then the issue must be within the Oil Pressure Switch. Need to be replaced. Otherwise, proceed with the step 2.
2. Disconnect wire from BCM module connection. If the problem is gone, then the issue is with the wire between the Switch and BCM. Wire needs to be replaced.
So my question is - if I run the bike with the Oil Pressure Switch wire disconnected for a short period of time, can it cause any issue?
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Joined: Jun 2019
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From: SE Michigan
i don't think you'll get anywhere by disconnecting the wire, in fact it may cause it not to run at all, i'd think you'd have to bypass it....but I wouldn't do that either....are you able to get to the wire that outgoing wire on the part your doubting and put a multimeter to it?
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From: Texas
On the Sensor side it is blocked by V&H pipe. Maybe on the BCM unit side I could.
However the challenge is that the Oil Light blink happens for a fraction of a second while hardly accelerating. So to detect grounding I would need some sort of recording device.
Could you please clarify how to bypass it?
However the challenge is that the Oil Light blink happens for a fraction of a second while hardly accelerating. So to detect grounding I would need some sort of recording device.
Could you please clarify how to bypass it?
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Joined: Jan 2007
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From: along the shore of Mishigami
A few things I would check primarily for security and tightness. 1) the plug from the Crank position sensor, it sends sends signals to the ECM to trigger ignition , 2) the connection to the ECM, I would disconnect spray some contact cleaner and reconnect, and 3) check the battery connections, make they are goud un tite.
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From: Texas
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Seasoned HDF Member
Joined: Jun 2019
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Likes: 10,767
From: SE Michigan
On the Sensor side it is blocked by V&H pipe. Maybe on the BCM unit side I could.
However the challenge is that the Oil Light blink happens for a fraction of a second while hardly accelerating. So to detect grounding I would need some sort of recording device.
Could you please clarify how to bypass it?
However the challenge is that the Oil Light blink happens for a fraction of a second while hardly accelerating. So to detect grounding I would need some sort of recording device.
Could you please clarify how to bypass it?
lets say we got a flame prover.....or a snap disc...(i know not a motorcycle, different industry, but all electricity works the same).one wire comes in one side and exits the other.....if we suspect the part is bad, we'll put alligator clips on both wires and close the circuit....if it didn't run before, and the bypass causes it to kick on, we know it's a bad part and replace it....if it still doesn't work, the part is good and you have to look elsewhere for a failure
the better way though is to use a multimeter and know what the readings should be...or have an idea..couple probes in the right place will tell you if you have juice going into that switch and juice coming out
hit up the fellas here in the tech mechanical section, there are way more experienced guys than me.....and welcome to HDforums....hope we can have you talking about how much you love your bike soon
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Joined: Jan 2021
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From: Texas
Yes. I was surprised about that too. Unless I am doing the code read the wrong way:
- Turn of ignition
- Press and hold Trip Reset button
- Turn on Ignition then release the Trip Reset button
- All illuminated, speedometer goes all the way up then comes back
- The word "diag" appears.
However, I do not see "PSSPt". Instead it brings me to ECM with number 0.
By pressing the Trip Reset I navigate ECM -> BCM-> ...
Each of those categories shows number 0.
May be ECM has an issue of registering codes...
- Turn of ignition
- Press and hold Trip Reset button
- Turn on Ignition then release the Trip Reset button
- All illuminated, speedometer goes all the way up then comes back
- The word "diag" appears.
However, I do not see "PSSPt". Instead it brings me to ECM with number 0.
By pressing the Trip Reset I navigate ECM -> BCM-> ...
Each of those categories shows number 0.
May be ECM has an issue of registering codes...