Throttle Position Sensor - Bob Gorman - BMW R850 Maintenance Manual

Copyright(c) 1997, Stephen Karlan (Dali Meeow) <dali@netrox.net> , Miami, Florida

Throttle Position Sensor - Bob Gorman

The throttle position sensor is located on the left throttle body. It is the black box
with an electrical plug extending from the bottom. The sensor is what ties the
mechanics of the throttle cable to the electronics of the Motronic.
The Motronic needs to know the position of the throttle so it can regulate gas
flow, timing, and other engine management functions. As you turn the throttle,
voltage is adjusted up and down in the sensor and relayed to the Motronic.
If you pull down the rubber cap from the electrical connector on the sensor you
will notice 4 wires. The wire closest to the rear (number 1 – red/white) is effected
by throttle openings up to 1/8th turn. Most surging occurs at very small throttle
openings so we want to make sure that the baseline voltage is correct. Our goal
is to equate a closed mechanical throttle with .370 to .400V.
Place the positive lead of the DVM (Digital Volt Meter) up into the plug
corresponding to wire number 1(red/white). On the newer bikes there is an
internal seal around the wire so use a needle or paperclip to penetrate the seal
and make contact with the wire. Attach the ground wire to a good unpainted bolt.
Turn on the bike but do not start. Note and record your initial TPS voltage so
you can go back to it if necessary. The voltage should read between 370 -
400mV. If not you'll need to loosen the two screws holding the sensor in place
and slowly rotate it one way or the other until the correct voltage is achieved.
Don't worry about messing it up, you can't. After the sensor reading is set, tighten
the sensor screws.
One last step, if the voltage during the setup process went above 400mV then
a fault may have been generated in the Motronic. This is easily reset by pulling
the number 5 fuse from the left and then replacing it. The Motronic is now reset
and the throttle position setting is right on spec.
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