Trouble code P0651
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Novice
Joined: Aug 2024
Posts: 19
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From: Florida
Trouble code P0651
So as the subject states, I received a check engine light that has a single code, P0651. The bike is running great and has no obvious signs of something not working. It’s been at the dealer for 3 days now and the bike is not under warranty and I fear what the repair is going to cost. I was told today they still can’t figure out what’s throwing the code. It was explained to me that it’s a trouble code with the canbus system and they are going through the wiring trying to find and issue but can’t. Is there any suggestions out there? I fear I’m going to have a hefty bill and still no resolution. It’s a 2018 Ultra Limited with about 5,500 miles on it. I’ve only owned it 2 weeks but bought it without a warranty, dummy me I guess. The bike doesn’t have any modifications done to it that I know of. Still has stock exhaust and no aftermarket lights or anything. I’m just pretty bummed about it. Hoping someone has some advice especially if I end up just cutting my losses and picking the bike up.
Road Captain
Joined: Aug 2008
Posts: 635
Likes: 388
From: Philadelphia Northeast
Have you tried just to clear the code? P0651 code is a 5V sensor power problem code. It is related to TMAP sensor and one of the twist grip sensors. Relatively easy to diagnose with just a multimeter.
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Novice
Joined: Aug 2024
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From: Florida
Thanks so much for your reply. Yes I reset the light a few times and it always came back on. Even tried disconnecting the battery for several hours and the light stayed off for about 2 ignition cycles and 5 minutes and the light came back on so I just brought to the dealer. Now, the dealer has had it for a week and said they can’t figure it out so they have to wait for some other technician to dedicate an entire day. I then night the service manual and looked at the wiring diagram and I saw that only those two sensors were on that wire so to me it shouldn’t be hard but I think the dealer already tried replacing the TGS and TMAP so they have to check for wire breaks or shorts to ground I guess?
Seasoned HDF Member
Joined: Aug 2008
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shops love electrical since it is time spent and not book rate.
could be in the wire, connections, sensors, sensors not calibrated and the ecu programming or the ecu itself as that is where the 5 volt is originated.
do not over look grounds and make sure the wiring follows factory routing. wires too close to plug wires can pickup EMF and corrupt data.
could be in the wire, connections, sensors, sensors not calibrated and the ecu programming or the ecu itself as that is where the 5 volt is originated.
do not over look grounds and make sure the wiring follows factory routing. wires too close to plug wires can pickup EMF and corrupt data.
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Novice
Joined: Aug 2024
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From: Florida
I’m thinking the shop is going to take the tank off and the fairing and trace the wiring and hope to find a pinched wire or something. I hope they find the issue soon!
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Seasoned HDF Member
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From this thread:
P0651 Code
P0651 5 Volt Reference 2 Out of Range, would appear to be a sensor that uses a 5 volt reference is having intermittent failures, MAP (Manifold Absolute Pressure), TPS (Throttle Position Sensor), CKP (Crank Position Sensor), TGS (Twist Grip Sensor), CTS (Coolant Temperature Sensor) and there are several more.
Diagnostic Aids (You will need a Harley Electrical Manual that gives you pin locations with numbers and wire colors for the ECM and other component connectors) It may be possible to locate the fault by disconnecting one component at a time from the 5-volt reference circuit while viewing the 5-Volt Reference circuit parameter with a Digital Multi Meter. Ignition ON, measure for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.
* If the voltage is less than the specified value, test for a short to ground on all the 5-volt reference circuits. If all circuits test normal, replace the control module.
* If the voltage is greater than the specified value, test for a short to voltage on all the 5-volt reference circuits, or the signal circuit, for each component associated with the appropriate 5-volt reference circuit. If all circuits test normal, replace the control module.
3. Connect each component associated with the 5-volt reference circuit, one at a time, while monitoring the voltage. The voltage should not change more than 1 volt.
* If the voltage display changes more than the specified value when a component is connected, replace the component.
P0651 Code
P0651 5 Volt Reference 2 Out of Range, would appear to be a sensor that uses a 5 volt reference is having intermittent failures, MAP (Manifold Absolute Pressure), TPS (Throttle Position Sensor), CKP (Crank Position Sensor), TGS (Twist Grip Sensor), CTS (Coolant Temperature Sensor) and there are several more.
Diagnostic Aids (You will need a Harley Electrical Manual that gives you pin locations with numbers and wire colors for the ECM and other component connectors) It may be possible to locate the fault by disconnecting one component at a time from the 5-volt reference circuit while viewing the 5-Volt Reference circuit parameter with a Digital Multi Meter. Ignition ON, measure for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.
* If the voltage is less than the specified value, test for a short to ground on all the 5-volt reference circuits. If all circuits test normal, replace the control module.
* If the voltage is greater than the specified value, test for a short to voltage on all the 5-volt reference circuits, or the signal circuit, for each component associated with the appropriate 5-volt reference circuit. If all circuits test normal, replace the control module.
3. Connect each component associated with the 5-volt reference circuit, one at a time, while monitoring the voltage. The voltage should not change more than 1 volt.
* If the voltage display changes more than the specified value when a component is connected, replace the component.
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Thread Starter
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Novice
Joined: Aug 2024
Posts: 19
Likes: 8
From: Florida
I bought a service manual that has the wiring diagram. I’m no electrician or technician but I do consider myself somewhat tech savvy and mechanically inclined. With that said, if I read the wiring diagram accurately, it appears that the 5v reference 2 only goes to the TMAP and TGS. The other sensors are for 5v reference 1 which would throw code p0641. I understand it’s still a lot of wire but I feel like it shouldn’t be as difficult as the dealer is making it seem to track down the cause for the light if all you’re dealing with is 2 sensors and one run of wire.
Banned
Joined: Aug 2021
Posts: 4,027
Likes: 6,286
From: SoCal
Your struggle sound very familiar, as I was having similar issues with our 2015 Jeep JKU.
it was randomly throwing codes and going into limp mode, making it undriveable.
Like the bike, they Jeep has multiple sensors that rely on that 5v signal and the dealer wanted over $1,000 just to diagnose - not even to repair - the problem.
I brought it home and took it apart myself.
Turned out to be an intermittent short at the oil pressure sensor where the wire insulation had degraded.
That and several of the injector connectors were brittle.
I spent about $50 on replacement connectors and spliced them into the harness myself.
I hope your issue is similarly simple to fix once isolated.
it was randomly throwing codes and going into limp mode, making it undriveable.
Like the bike, they Jeep has multiple sensors that rely on that 5v signal and the dealer wanted over $1,000 just to diagnose - not even to repair - the problem.
I brought it home and took it apart myself.
Turned out to be an intermittent short at the oil pressure sensor where the wire insulation had degraded.
That and several of the injector connectors were brittle.
I spent about $50 on replacement connectors and spliced them into the harness myself.
I hope your issue is similarly simple to fix once isolated.
