Author Topic: Gear Position Indicator  (Read 17967 times)

Offline frankenduck

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Gear Position Indicator
« on: May 29, 2011, 08:17:17 AM »
more troubleshooting of the gpi click here..

The digital gear number display in the right side of the tachometer faceplate is known as the gear position indicator. (GPI)  It is driven by a rotating switch forward of the swing arm on the back of the transmission. It has a ground for input and three output wires:  yellow/blue, yellow/black and yellow/white.  The GPI circuit board inside of the instrument cluster determines/displays what gear you're in based upon which combination of the three yellow/other color wires are grounded.  (See graphic below.)  When all three of the yellow/other color wires are gounded then the GPI circuitry knows that the transmission is in neutral.  When in neutral, the GPI circuitry displays zero and sends 12V to illuminate the neutral light in the instrument cluster and also to the starter button in the right combination switch via a black/green wire.


Living where it does on the back of the transmission, the GPI switch has a hard life and is eventually prone to decomposition and failure.  This is the reason why the gear number displayed in the instrument cluster may be wonky after riding in the rain or washing your bike.


If your GPI is acting up then the first thing to do is to diagnose whether your problem is caused by the GPI switch on the transmission or the GPI circuit board in the instrument cluster.  This is easily accomplished by grounding the various wires at the connector under the right side battery cover per the chart in the diagram above.

If you determine that the switch is the problem then the final drive and swing arm need to be removed in order to access/replace the switch.

If you determine that the GPI circuit board is the problem then this can be replaced as a separate part without having to replace the entire instrument cluster assembly.  To replace the GPI circuit board:

1 - Remove the instrument cluster from the bike.

2 - Place the cluster upside down on a towel/rag to protect the front of it from scratching.

3 - Remove the nine (seven on 85 and earlier bikes) Philips screws around the perimeter of the back of the instrument cluster to remove the backplate.

4 - Once the backplate is removed, remove the six Philips screws that hold the instruments inside the instrument cluster housing.  There is one screw on each side and four at the bottom center.

5 - Remove the two recessed screws from the back of the tachometer.  These screws are what hold the GPI circuit board in place.

6 - Pull the trip odometer knob out to the extent that it's spring will let you and carefully shake the instruments out of the housing.  (Be very careful from here on out as the speedo and tach needles will bend if you look at them crossways.)

7 - From the side, remove the white plastic spacer that was held in place by those two screws.

8 - It's a tight fit but you can then carefully pry the pins of the GPI circuit board off and slide it out from the top.

9 - Reassembly is the reverse of disassembly.
Once I had a Collie pup. Dug a hole and covered him up. Now I sit there by the hour. Waiting for a Collie-flower.
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Offline frankenduck

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Re: Gear Position Indicator
« Reply #1 on: June 16, 2012, 04:21:12 PM »
UPDATE - 6/16/12:  Added a PDF on replacing and testing the GPI circuit board to the original post.
Once I had a Collie pup. Dug a hole and covered him up. Now I sit there by the hour. Waiting for a Collie-flower.
New to K bikes? Click here.
K Bike Maintenance & Mods: Click here.
Buy parts here.
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Offline fastcar

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Re: Gear Position Indicator
« Reply #2 on: June 07, 2015, 09:24:19 PM »
Thank you for this excellent resource. Based on this I have determined that the 'Transmission Switch' PN 61 31 1 459 593 on my K75 is faulty. If you didn't want to pay $115 for a new one, where would you look? Does anyone have suggestions? Haven't had any luck hunting online yet. Thanks…

fastcar  :bmwsmile

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