Switches and Sensors for Commercial Vehicles: Switches, TPMS and HMI

Technical Overview Updated October 2026

The BCM decides what the cabin is doing. The switches and sensors tell it what the driver and the world are doing first.

A heavy-truck dashboard now carries 30 to 60 active inputs. A bus cabin adds another 10 to 20 for passenger interaction. A construction-machinery cab adds rotary selectors, dump-bed controls and overload switches that a passenger-car designer would never see. Almost none of it can be wired the way it was a decade ago, because the harness count and the dashboard real-estate budget both ran out. The whole layer rebuilt itself around CAN switch panels, LIN-attached domain controllers and a small set of hard-wired functions that legal and safety reasons keep off the bus.

This guide is written for OEM purchasing and engineering teams scoping that layer for heavy trucks, buses, construction machinery and new-energy commercial vehicles. It covers what each switch and sensor category does, how the cabin HMI partitions across CAN switch panels / mechanical switches / LIN-attached door & window controllers, how the chassis sensor stack (TPMS, rain-light, fuel-level, axle-load) talks to the BCM and instrument cluster, what binds them through CAN / LIN / hard-wire / UDS, and where the Youlai EDK / JDK / TDK / YDK / CGQ / FMQ catalogue fits across the six product families. For the product catalogue itself, see the Switches & Sensors category page; for the receiving side — the BCM that consumes all of these signals — see the Smart Control Modules technical guide. For choosing between the three switch interfaces themselves — CAN, LIN or hard-wired — see the CAN vs LIN vs hard-wired switches comparison.

1. What the switches and sensors stack does

A modern commercial-vehicle cabin and chassis carry five overlapping layers of input hardware, each with its own electrical philosophy. Naming varies by program but the partition is fairly stable. For how this input layer connects to the control, network and power layers behind it, the commercial-vehicle E/E architecture guide takes the whole-vehicle view:

• CAN switch panels and HMI — concentrated button panels that replace 10 to 30 discrete switch wires with a single CAN node. EDK-907 (CAN-bus panel, 18–32 VDC, IP53) and EDK-2507 (four-button CAN rotary, 9–32 VDC, IP66) sit at the top of the catalogue, talking on the body CAN to the BCM and gateway. Used heavily on heavy-truck cabs and modern bus driver consoles where the dashboard switch count has outgrown the harness budget.
• Mechanical, rocker and momentary switches — the dashboard grid that never disappears. Rocker, toggle, hazard, emergency cut-off, push-start, headlamp leveller, CNG / ESP-off, ignition and door-lamp. JDK-901, TDK-901, TDK-902 / TDK-905, TDK-904, JDK-2425. Most of these are hard-wired. The safety and fail-safe subset — hazard, emergency cut-off, ignition — has to operate with the BCM asleep, so it stays on a protected battery-direct feed rather than behind a controller output; the rest (push-start, headlamp leveller, the CNG fuel-mode / ESP-off signals on the TDK-904) are hard-wired signal inputs a controller reads, not battery-direct fail-safe functions.
• Door, window and mirror switching — the cabin interior switches that sit on LIN or short hard-wire runs from a BCM-adjacent door controller. EDK-908 LIN power-window, EDK-2212 door panel, EDK-2319 mirror, TDK-2202/3 power-window (the 12 V passenger / new-energy part, not a 24 V cab switch), TDK-2306 / TDK-2307 door & mirror, EDK-914 LIN power-window switch. EDK-908B is not in that LIN set: 9–32 V, one CAN line and one 24 V / 500 mA hardwire. On a heavy-truck tractor cab, the LIN switches in this group are typically attached to the BCM through a dedicated door controller; on a light-truck cab they may sit directly on body-CAN. For how a buyer chooses among the LIN panels, see the power-window & door switch panels buyer guide.
• Bus accessibility and stop-request hardware — a niche of the catalogue with its own regulatory pressure. JDK-2207 standard stop-request, JDK-2209 disabled-passenger, JDK-2306 vibration feedback, TDK-2406 / TDK-2407 wireless. Wireless variants are paired against the EBX-2404 bus wireless receiver on the BCM side. Used on intercity buses, city buses and accessibility-compliant programs.
• Sensors and acoustic devices — the inputs that monitor the vehicle and the cabin announcement layer. TPMS sensors (YDK-902 valve-stem, YDK-903 clamp-mount, EBX-957 receiver), windscreen light-and-rain sensors (CGQ-024A / CGQ-024B) and the CGQ-012A ambient-light assembly, temperature-threshold switches (the YL02-WK family) and fuel-level senders (project-specific capacitive and resistive types), buzzers (FMQ-024A 24 V), AVAS / multi-function audible alert (EBX-2406), HV battery-pack protection (JDK-2509, 1500 VDC, 250 kA breaking, IEC 60269-7 aBat). TPMS, the light and rain sensors, and the temperature and fuel senders are inputs. Buzzers and the AVAS module are outputs. The HV fuse is protection.

One detail often overlooked is how this partitioning has shifted in the last five years. A decade ago the typical heavy-truck cab had 40 discrete switch wires reaching the BCM, two TPMS systems offered at the wheel hub, and a hard-wired buzzer behind the dashboard. Today the same cab has one or two CAN switch panels owning the central dashboard, LIN-attached door and window modules handling the side panels, a CAN-attached TPMS receiver feeding the instrument cluster, and a CAN-attached AVAS module handling pedestrian warning on the EV variants. The hard-wired layer did not disappear; it shrank to the seven or eight functions that the safety case and the cold-start requirement keep on a dedicated harness.

2. CAN switch panels, mechanical switches and cabin HMI

The cabin HMI is where the switches conversation gets the most weight on a heavy-truck or bus program. The driver touches it every day, the OEM body engineering team carries it through the longest review cycle, and the regulator looks at it more carefully than any other part of the body electrical architecture.

A useful way to look at it is by electrical philosophy, not by switch shape:

• CAN switch panels — EDK-907 and EDK-2507 are the working horses on heavy-truck cabs that have moved their dashboard switch grid to a bus node. EDK-907 carries 8 to 12 illuminated buttons on a CAN segment, 18–32 VDC supply, IP53 sealing for cab-interior duty, with a hard-wire backup path on the safety-critical buttons (engine kill, hazard) so the function survives a CAN failure. EDK-2507 is the four-button rotary variant, 9–32 VDC, IP66 sealed for the harsher mounting positions (door pillar, console edge) where wash-down or beverage spillage is a real risk. A program that adopts these panels saves roughly 40 to 60 percent of the dashboard switch harness mass; the trade is a more capable BCM at the receiving end and a documented CAN message map between the two. The EDK-2403 is the dual-rotary CAN variant of the same idea — two infinite-rotation encoders with 4-way select and a press-to-start knob for menu, climate and mode control rather than a fixed button grid.
• Console request switch — EDK-2213: an EPB paddle and an Auto Hold button, one CAN channel and one 500 mA hardwire output at 9–32 V. It is a request device — the EPB control unit performs the clamping and owns the fault strategy.
• Mechanical, rocker and hazard — JDK-901 rocker, JDK-2201 3-position sealed toggle, TDK-901 hazard and the various door-lamp variants (TDK-906 / TDK-907 / TDK-908) are the discrete panel switches that typically stay hard-wired rather than moving to a bus node. Within this group the true fail-safe subset is narrower: hazard lights are normally required to work with the vehicle switched off and the body network asleep, so on most programmes that circuit stays on a protected battery-direct feed rather than moving behind a controller. A general-purpose dashboard rocker such as the JDK-901 is a hard-wired panel switch whose controlled function and contact rating are set per programme — useful and reliable, but not in itself a battery-direct safety device.
• Push-button and momentary — TDK-902 and TDK-905 push-to-start, TDK-2513 round self-reset button, TDK-2514 pre-ignition switch, TDK-2408 dual-pedal switch. The push-start functions are increasingly paired with a PEPS controller (EBX-964 standalone or EBX-2169 integrated PEPS-BCM) for keyless entry, but the underlying button itself is still a hard-wired momentary input fed into the PEPS logic block. That same keyless controller also drives the electronic steering-column lock (ESCL) — the EDK-911 — which, unlike the hard-wired switches above, is a motor-driven actuator that locks or releases the column only on a command from the controller, not on a battery-direct feed.
• Emergency cut-off — JDK-2425 is the mushroom-head emergency stop for heavy trucks, construction machinery and buses, 9–32 VDC, 10 mA–10 A across the contact pair, IP67 sealing, 100,000 operation cycles, 360 hour salt-spray validated, REACH and ELV compliant. It stays hard-wired; a circuit above 10 A is broken through the control side of a contactor or battery isolator, not through the switch contacts.
• Door, window and mirror — EDK-908 LIN power-window, EDK-908B (CAN + one 24 V / 500 mA hardwire, 9–32 V), EDK-2212 door panel, EDK-2319 mirror, TDK-2306 / TDK-2307 door & mirror. EDK-908, EDK-2212, EDK-2319 and TDK-2306 / TDK-2307 sit on LIN or short hard-wire runs because the bandwidth requirement is low (switch state, motor position) and the BCM owns the logic. On a heavy-truck tractor cab the LIN segment off the BCM is typical; on a bus the cabin interior switches may sit on a dedicated body sub-CAN to reach the second deck or the articulated bus rear section. The door-mounted EDK-2010 is a different case — a hard-wired IP67 cab-door service panel (cab-tilt, ground-level engine start / stop, hazard) rather than a LIN window / mirror cluster.
• Bus stop request — JDK-2207 standard, JDK-2209 disabled passenger, JDK-2306 vibration feedback for the partially-sighted, TDK-2406 wireless reminder, TDK-2407 wireless disabled. The wireless variants pair against the EBX-2404 bus wireless receiver, which drives a general stop-request output and a separate accessibility output to the driver console and annunciator. Accessibility compliance for city-bus programs is the main driver here; the regulator looks at it as a safety case rather than a comfort feature — the bus stop request button buyer guide walks through the wired-versus-wireless choice and how a press reaches the driver.

The CAN switch panel decision locks in more of the downstream architecture than it first appears. Once the cabin moves to a panel like EDK-907 or EDK-2507, the BCM increasingly comes CAN-FD-capable on at least one channel to leave bandwidth headroom for the panel and the gateway, the diagnostic tool has to read panel button state through UDS rather than back-probing a wire, and the harness build at the OEM assembly plant changes shape entirely — fewer wires, more connectors, more end-of-line panel-flash steps. The harness saving is real but it is not free.

3. TPMS, rain-light, fuel-level and acoustic devices

The sensor and acoustic side of the catalogue is where commercial vehicles differ most sharply from passenger cars. The duty cycles are longer, the working temperature bands are wider, the mounting positions are harder to reach for service, and the regulatory pressure is now real on the safety-critical sensor families — TPMS in particular.

• TPMS — tyre-pressure monitoring. YDK-902 (valve-stem mount, 433.92 MHz, 5 to 8 year battery, IP66) and YDK-903 (clamp-mount sibling for wheels that do not accept a valve-stem sensor — non-standard rim geometries, special trailer and mining wheels — same RF and battery envelope) cover the sensor side; EBX-957 (24 V TPMS receiver, 433.92 MHz frequency-hopping spread spectrum, IP67, Deutsch DT06-4S connector) sits on the chassis CAN and decodes the sensor frames. The packet rate goes up when the wheel is rotating and the frame carries pressure, temperature and a per-wheel ID. The hard part is not the radio link; it is the end-of-line auto-learn that binds the four or six wheel IDs to the receiver, and the diagnostic strategy when a sensor battery reaches the end of its 5 to 8 year life on a fleet vehicle 200,000 kilometres into a duty cycle.
• Rain and light sensing. The catalogue part CGQ-024A-SYN reports light and rain on CAN (Deutsch DT04-4P) and is rated 12 VDC and 24 VDC, while the CGQ-012A is an ambient-light assembly whose published output is a low-level signal on pin 2; its temperature and sunlight pins are reserved. The rain reading is for automatic wipers, and the light reading is for automatic headlamps. For how the light-and-rain sensor differs from the ambient-light assembly, see the rain and light sensor buyer guide.
• Temperature thresholds and fuel level. YL02-WK is the temperature-switch family — a sealed probe that closes or opens a dry contact at a set point between 30 and 155 °C and resets by itself on cooling, ordered by a part-number code that fixes the set point, the contact form and the mounting style. It is a threshold device, not a measurement one, and it is general-purpose rather than vehicle-specific: Youlai lists it for transformers, engines, integrated circuits and general electrical equipment, and the engine application is what puts it on trucks and machinery. Separately, capacitive and resistive fuel-level senders are quoted per harness drawing because tank geometry varies more than any catalogue can predict. Where the build has a BCM in that path, it reads a temperature switch as a digital input and the fuel sender as an analogue one, then publishes the over-temperature alarm and the fuel-level percentage on body CAN for the instrument cluster to display.
• Acoustic devices. FMQ-024A is the 24 V cabin buzzer used on service-vehicle warnings, machinery operator alerts and bus accessibility chimes. External horns, voice annunciators and loud-hailer variants are confirmed against the program acoustic specification because the rated SPL is project-driven (75 dB cab, 85 dB AVAS, 110 dB external horn are the typical bands). The EBX-2406 multi-function audible alert module sits on body CAN at 85 dB and covers AVAS / turn / blind-spot duty on the new-energy bus and commercial-vehicle programs that mandate pedestrian warning at low speed.
• HV battery-pack protection. JDK-2509 sits in a sensor and protection slot rather than a switch slot because its job is to monitor and break a fault current on the EV traction-pack bus. 1500 VDC rated, 250 kA breaking capacity, qualified to the EV-specific IEC 60269-7 aBat envelope at a TÜV-accredited type-test laboratory. Available current ratings 1250 to 3000 A. On a heavy-duty electric truck or bus this is the in-line HV fuse body that the BMS and the BCM both depend on for the worst-case short-circuit response; the BMS opens contactors on the millisecond scale, JDK-2509 clears the fault current on a much shorter timescale and independently of the contactor logic when the contactor path is too slow.

One detail that often slips out of early RFQ conversations is the wheel-ID auto-learn workflow for TPMS. On a fleet truck that rotates tyres every 100,000 kilometres, the receiver has to be re-paired four or six times across the vehicle life. A supplier that ships a TPMS pair (sensor plus receiver) without a documented auto-learn procedure for the end-of-line tester and the field-service tool is one that the dealer network will end up working around manually. Worth asking at the RFQ stage rather than discovering at the first wheel rotation. For the full sourcing walk-through — sensor mounting, the RF-to-CAN signal path and how to spec a system — see the heavy-truck TPMS buyer guide.

4. CAN, LIN, hard-wire and UDS — how the inputs reach the BCM

The switches and sensors stack is held together by four electrical philosophies, each with its own job. Mixing them up at the RFQ stage is one of the easiest ways to mis-spec a program.

• Hard-wire. Anything that the safety case or the regulator requires to operate with the BCM asleep stays on a dedicated harness fed from a protected battery-direct supply. Hazard light, emergency cut-off, ignition, cabin-lighting and door-lamp courtesy switching. On a heavy truck this is roughly seven to ten functions that simply do not move to a bus. The wire count is small but the harness-side discipline is high — these wires take the worst short-to-ground and short-to-battery faults that the cab will see in 15 years of service.
• CAN 2.0 and CAN-FD. The body bus on a heavy-truck cab is normally CAN 2.0 at 250 or 500 kbit/s; the powertrain bus on new-energy variants increasingly runs CAN-FD because the VCU and BMS exchange more data per cycle than CAN 2.0 sustains. CAN switch panels (EDK-907, EDK-2507) sit on body CAN; TPMS receivers (EBX-957) typically sit on chassis CAN to reach the instrument cluster directly; AVAS modules (EBX-2406) sit on body CAN to coordinate with the BCM lighting state.
• LIN. The low-bandwidth single-wire bus from the BCM to its specialty controllers. LIN door switch (EDK-914) and mirror adjust modules. (Anti-pinch window controllers such as the EBX-2206 sit on CAN, not LIN.) LIN tops out at 19.2 kbit/s, which is plenty for switch state and slow analog signals but nowhere near the bandwidth needed for the CAN switch panel or the TPMS receiver. Putting a TPMS receiver on LIN would starve the instrument cluster of per-wheel pressure data; putting a door switch on body CAN would burn a node ID for a function that only the BCM and the door module need to see.
• RF 433 MHz. TPMS (sensor to receiver) and the RKE fob are one-way at 433.92 MHz. That band is global-harmonised for short-range automotive use, which simplifies type approval but also means the receiver has to deal with cross-talk from adjacent vehicles in a busy yard. EBX-957 uses FHSS specifically to reject the cross-talk; the YDK-902 and YDK-903 transmitters hop on a wake-up pattern that the receiver demodulates per wheel ID. Wireless stop-request transmits at 433.07 MHz.
• ISO 14229 UDS. Where a part uses UDS, it is tuned per project and addressed from the OEM scan tool, the production-line tester and the dealer service tool. Read DTCs, clear DTCs, read identification, write configuration (TPMS wheel-ID auto-learn, panel button mapping), run actuator tests. UDS is what makes a TPMS pair or a CAN switch panel supportable across its 10 to 15 year life on a commercial-vehicle program; an ECU without UDS is one that the dealer cannot service when a sensor battery dies or a panel button stops responding. In-house EMC pre-compliance screens for radiation before formal EMC — a CAN switch panel that radiates wrong shows up first as bus errors before it shows up on a regulatory test sheet. The formal test is at a third-party laboratory when the programme requires it.

The interaction matters. A CAN switch panel placed on a body bus that runs at 125 kbit/s will burn airtime that the BCM needs for wake-up messaging; the same panel on a 500 kbit/s segment behaves cleanly. A slow update on the sensor bus cannot feed a wiper module that expects a faster spray reading; the timing margin closes. An RF 433 MHz TPMS receiver mounted near the BCM cable harness without proper shielding will see frame loss above 20 percent in a noisy industrial-machinery cab, even though the receiver datasheet says IP67 and CAN integration is fine.

5. Where the Youlai EDK / JDK / TDK / YDK / CGQ / FMQ catalogue fits

The Youlai switches and sensors catalogue is built around six product families, each addressing a slice of the cabin and chassis input layer. The naming convention reflects the function rather than the bus: an EDK part is normally a switch panel or door / window module, a JDK part is normally a mechanical or rocker switch (plus the JDK-2509 HV fuse that sits in the EV protection slot), a TDK part is a push-button or pre-ignition or wireless device, and YDK is TPMS sensors plus the RKE fob, CGQ is light and rain sensing, and FMQ is acoustic devices.

PPAP, IMDS, FCC, SASO, e-Mark and EAC documentation are available upon project requirement rather than as catalogue documents.

If the program has not yet decided which switches sit on a CAN panel, which stay on hard-wire and which delegate to a LIN-attached domain controller, the best starting point is to scope the function list against the cabin HMI plan first, then add the chassis sensor stack (TPMS, rain-light, fuel-level), and finally add the acoustic devices and HV protection based on the new-energy decision. The supplier conversation goes more smoothly when the stack is sketched on one sheet rather than negotiated module-by-module across several email threads — for an architecture review against an existing program brief, the project workflow is on the CAN bus switch panel and commercial vehicle sensor manufacturer pages.