Selecting Fleet Speed Sensors and Senders for Trucks and Buses

Which speed sensor does a truck or bus need?

The right speed sensor is the one whose probe length, thread, connector and output type match the gearbox drive and the instrument or tachograph it feeds. A fleet runs a mix of these across makes and model years, so the part number on the old sender, not the vehicle name alone, is what gets you the correct replacement. Get any one of the four dimensions wrong and the sender either will not seat or the gauge reads false.

Three sender families cover most commercial fitments:

• Speed pulse generators that thread into the gearbox and feed an electronic speedometer or fleet-management unit.
• Integrated pulse generators with a fixed probe that read a target wheel inside the housing.
• KITAS tachograph senders that feed a certified digital head with an encrypted signal.

How do I read a pulse generator part?

Match four things against the old unit before ordering.

Thread and connection. A threaded speed pulse generator often uses an M22 x 1.5 fitting with a 4-pin connector, for example a 4-pin M22 x 1.5 female-connector unit. The thread seats it in the gearbox; the connector has to match the loom plug on the truck.

Probe length. An integrated pulse generator reads a target ring at a set depth, so the probe length is fixed by the housing. A 35 mm probe unit and a 19.8 mm probe unit are not interchangeable even when the connector looks identical. Measure or read it off the old part.

Output type. Inductive output suits most electronic speedometers and fleet telematics. An encrypted output is specific to a certified tachograph head and will not drive an ordinary gauge. Do not substitute one for the other.

Connector gender and terminal. A 4-pin round terminal and a 4-pin M22 female connector are different plugs. Confirm gender and terminal style so the loom mates first time.

Inductive or encrypted: which output do I order?

Order by what reads the signal. If the sender feeds a speedometer, an odometer, a rev counter, or a third-party fleet-management box, you want an inductive pulse generator. If it feeds a certified digital tachograph, you want the matching KITAS sender with the encrypted output, and it has to be paired and sealed by an approved workshop after fitment.

Mixing these is the most common fleet ordering mistake. An inductive generator fitted to a tachograph drive will throw a sensor fault and break certification; a KITAS sender wired to a plain speedometer will not read at all.

How do I keep fleet ordering consistent?

Build a small fitment sheet per vehicle class: gearbox type, sender part number, probe length, thread, connector, and output. Order against that sheet, not against the driver’s description of the fault. For senders that pair with a tachograph, log the calibration date alongside the part so the recalibration slot is booked before the seal expires.

Where a part has a lead time, plan the swap around a scheduled service rather than grounding the vehicle. Senders are low-cost relative to downtime, so a small shelf stock of the high-runner pulse generators pays for itself on a mixed fleet.

How to order or request a quote

Give us the old sender part number, or the gearbox type and what the signal feeds (speedometer, fleet unit or tachograph), and we will confirm the correct probe length, thread, connector and output before you commit. Order by part number on Omnipart, with trade pricing on volume: the VDO 4-pin speed pulse generator for an M22 x 1.5 port (2159-01000000) and the VDO integrated pulse generator with a 35 mm probe (2159-20102201) are two of the common fleet parts.