Author Topic: ABS Wheel Speed Sensor Phase Shift problem  (Read 2362 times)

Thebmwman

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ABS Wheel Speed Sensor Phase Shift problem
« on: February 20, 2024, 10:08:13 AM »
Friends, I need help understanding this issue.
We are talking about a BMW R1200GS LC with the following code in the ABS module: 0x480903 "Wheel speed sensor, front, phase shift."
The fault occurs unexpectedly, and when this happens, the traction control engages, drastically reducing the motorcycle's acceleration.
When the fault occurs, the traction control icon flashes, indicating that the motorcycle has detected a slipping or skidding condition.
I cannot find a specific pattern of failure; the issue occurs randomly.
I've attached an auto scan of the motorcycle with various faults, and the one that concerns me at the moment is related to traction control and ABS.
I have seen similar faults in BMWs before, but the term "phase shift" puzzles me.
That's why I'm contacting your knowledge and goodwill to comprehend and address this issue. Thank you very much in advance for your valuable assistance.

TRJeff

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Re: ABS Wheel Speed Sensor Phase Shift problem
« Reply #1 on: February 20, 2024, 04:45:07 PM »
check front and rear speed sensors, rear securing bolt should be tight, front should be adjusted for proper distance from tone ring and secure. sorry I do not know proper distance for sensor but you should be able to find online.

GS Jim

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Re: ABS Wheel Speed Sensor Phase Shift problem
« Reply #2 on: February 20, 2024, 07:02:09 PM »
You didn't mention what year the GS is as you probably figured it would be in the auto scan that is not attached.
There is no adjustment for the proximity sensors, the correct installation sets the distance. Perhaps remove, examine and reinstall them.
Have you done any work at all to the bike before this issue arose?
Check the installation of the front wheel in regards to the wheel spacer, getting this wrong can cause all sorts of issues. Also examine the encoder ring for integrity.

Is this the "phase" wording you are referencing (from the code site) "The long-time monitoring of the ABS control phases checks whether the brake pressure reduction phase and the following brake pressure holding phase are too long. This is detected by way of the signalled wheel speeds." ?

The rest of the code reads thus:

Fault Time Condition
Air gap between wheel speed sensor and sensor ring too large.The wheel speed sensor is faulty Sensor ring faulty The electronic wheel sensor module operates under fault conditions.

Service Plan
Check for correct installation of wheel speed sensor.Check wheel speed sensor and sensor ring for dirt contamination.Check air gap between wheel speed sensor and sensor ring.

Fault Impact
ABS control function deactivated Partial integral control deactivated Rear wheel lift-off detection deactivated Vehicles with {Keyless Ride}: Ignition cannot be switched off.

Warnings
Warning Lights   ABS indicator and warning lamp active
Control Center Messages
   
Service Notes
On vehicles with {Keyless Ride}, the fault may mean that it is not possible to switch off the ignition by briefly pressing the ignition switch.
In this case, switch off the ignition using a long press (at least 5 seconds).

Thebmwman

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Re: ABS Wheel Speed Sensor Phase Shift problem
« Reply #3 on: February 20, 2024, 09:07:27 PM »
Finally found the problem.
A damaged wiring in the front wheel sensor was the culprit.
I do not know why the auto .scan PDF did not attach but it is a 2017 year model GS.
Never before have I seen this code in GS or any other bike or car brand, and that was the reason why to find help.

Cheers friends

GS Jim

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Re: ABS Wheel Speed Sensor Phase Shift problem
« Reply #4 on: February 20, 2024, 09:48:58 PM »
Hopefully not a hard (or expensive) fix then, splice perhaps?

As has been posted on this site in multiple places I have found a good search page for most codes is https://bmwfault.codes/ , in the case of this code one must drop the "0x" to make the search successful.

botus

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Re: ABS Wheel Speed Sensor Phase Shift problem
« Reply #5 on: March 27, 2024, 01:25:04 PM »
its normal on BMW bikes for the senor wires to snap - usually its the rear one - specially routed with cable ties to deliberately stress one section till they break - on the earlier bikes it also flags a snapped rear sensor as the front

that fake diagnostic confusion comes from limited / budget diagnostic capability - ABS will feed different signals based on grip each wheel sees - and thus the bike doesn't care if the rear is feeding interesting info (it just thinks the grip levels are bad on the back wheel when braking - but on early ASC traction control, all they did was try to judge if both wheels speeds are the same under acceleration by using the ABS sensors - so a part broken intermittent signal from a failing rear ABS sensor throws the ASC in to a meltdown of no grip - so it kill the engine

ALL BMW riders need to know this - so they can switch out traction control and ride home rather than get the vehicle recovered over nothing !

the best bit as the system just knows there's a massive difference in wheel speed, but not which was slipping, so, Quick throw an error code - as I don't know which, just pull the first code in the list - which is the front senor failure

what else happens when it has the inertia sensor picking up info on later bikes I don't know (optional from 2015)