Triumph Gear Position Sensors Analyzed

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Triumph motorcycles use an electronic gear position sensor to determine the position of the gear shifter. The description of the gear position sensor from the service manual is below:

The gear position sensor is situated in the lower crankcase below the final drive belt pulley. The gear position sensor provides the ECM with selected gear information. This is used to prevent the engine from starting if the transmission is in gear. The sensor also provides information to the neutral lamp in the instruments.

-- Triumph Service Manual

While the Triumph Thunderbird Storm, Thunderbird LT,  Rocket III, and Speed Triple all have different part numbers for the sensor, the sensors operate in the same way. The differences between models are likely due to either physical size and mounting, or having a slightly different sensing system.

The similar gear position sensors are Triumph part numbers T1190814, T1292057 and T1290666 (Thunderbird Storm). Triumph does not manufacture these sensors, but buys them as an OEM product from an automotive electronics manufacturer.

Triumph Gear Position Sensor For Newer Models

The gear position sensor for newer models has 7 electronic switches that are activated. The gear selector moves through the 1-N-2-3-4-5-6 positions in sequence. These switches connect increasing resistance values to electrical ground through a fixed resistor in the Electronic Control Module (ECM), and this creates a different output voltage for each gear. The computer inside the ECM reads the voltage to determine which gear the bike is in.

This design reduces the amount of wiring and the size of the connector and harness between the gear position sensor and the ECM. Only 4 wires are required: one for the voltage, one for the neutral position (for compatibility with older designs), one for power, and one for ground. Connecting the switches directly to the ECM instead would require a minimum of 8 wires.

The sensor for older Triumph bikes uses 3 wires instead of 4. These sensors are likely based on a variable resistor element instead of the switched resistances of the new models. Triumph may have moved to the switched version because of improved longevity and reliability  -- variable resistor elements are prone to wear.

The ECM uses the gear position information to operate the ignition, the neutral light, and adjust the timing or fuel mixture.

The ECM in Triumph motorcycles also transmits the gear information to the CANBUS network within the bike's wiring. The diagnostic connector connects to the CANBUS network with a proprietary communication protocol and not as OBDII (1).  The Gearingo gear indicator has the internal circuit to listen to the CAN communication. The Gearingo then deciphers the messages and displays the gear for the rider.

(1) OBDII communication is available on the diagnostic connector, but as a K-LINE signal and not CANBUS

Triumph motorcycle gear position sensing block diagram

Cut-Apart View of Gear Position Sensor

I took apart a Triumph gear position sensor to see what is inside of it, shown in the picture below. The sensor has the following basic components:

  • Sensor housing with two mounting ears.
  • Rotating disk with a small magnet that attaches to the bike's gear selector assembly within the camshaft housing.
  • Printed circuit board that has 6 Hall Effect sensors that detect the location of the rotating magnet.
  • Cable and connector that connects the sensor to the main connector on the ECM module. This cable has a braided sheath on it to protect the wiring against heat and abrasion.

 

Triumph Gear Position Sensor Tear Down

Gear Position Sensor Schematic

The simplified schematic in Figure 3 below depicts the gear position sensor's internal circuit. The transistors marked Q1-Q7 are actually hall effect switches that are positioned in a circular pattern around the center of the unit so that the small magnet rotates over, and activates, them in sequence. 

Triumph Gear Position Sensor Internal Schematic
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