Checking the Input And Output Speed Sensors For the Transmission

Fig 1: Identifying Transmission Control Module Connector

Courtesy of VOLVO CARS OF NORTH AMERICA.

NOTE: The transmission control module (TCM) must not be connected.

Connect the breakout box. See Connecting the breakout box

NOTE: Do not damage components and terminals when test measuring. Handle components and terminals carefully.

Check 1

Connect an ohmmeter between the sensor terminals on the breakout box. Check the resistance. The resistance must be more than 1 MΩ but not infinite.

For transmission input speed sensor:

terminal #12 and #13 on the breakout box

For transmission output speed sensor:

terminal #19 and #20 on the breakout box

NOTE: Check the resistance using an ohmmeter which can measure resistances above 10 MΩ.

If the resistance is 0 Ω it means that the cables are short-circuited to each other or that the sensor is faulty.

If resistance is infinite it means that there is an open circuit in the circuit.

Check the wiring. Measure the resistance between a terminal and a ground point.

If the resistance is 0 Ω it means that the cable has a short-circuit to ground.

If resistance is infinite it means that there is an open circuit in the circuit.

Check 2

Connect a temporary voltage supply to:

transmission input speed sensor:

terminal #A12 on the breakout box

transmission output speed sensor:

terminal #A19 on the breakout box

Connect a temporary ground terminal via a 100 Ω resistor and an ammeter/voltmeter to:

transmission input speed sensor:

terminal #A13 on the breakout box

transmission output speed sensor:

terminal #A20 on the breakout box

Move the gear selector lever to gear position N . Raise the vehicle so that the drive wheels hang freely. Measure the current/voltage while spinning the wheels in the same direction. For values see the table below.

Component	Note	Current (mA)
Transmission input speed sensor Transmission output speed sensor	Current between the sensor terminals	High = 12-16 mA Low = 4-8 mA

Component	Note	Voltage (V)
Transmission input speed sensor Transmission output speed sensor	Voltage between the sensor terminals	High ≈ 1.4 V below U_bat Low ≈ 0.8 V below U_bat