Platform · Remote Diagnostic
Most platforms read the vehicle. MOS4 reads it and talks back.
Open a live session from the cloud over a signed TLS tunnel. Read, reset, reconfigure, attest and reflash. Same UDS (ISO 14229) / J1939 / ISOBUS / Modbus / SAE J2534 passthrough engine that drives autonomous telematics — different mode of operation.
What it does in the field
Five jobs the OS handles without a wrench.
For the subset of field failures that do not need a workshop, the OS opens a signed session, drives the bus, completes the action, closes. Saves a tow, a dealer visit, or the cost of dispatching a technician.
OEM · warranty operations
ECU reset over the air
Vehicle stalls on the highway. The remote server opens a signed session, resets the wedged ECU (Electronic Control Unit), closes. Driver continues. No tow truck, no dealer visit.
Saves: Saves one truck roll plus the dealer-bay slot.
EV maker · battery certification
Live-monitor certification
Drive the battery through a charge / discharge cycle while reading live cell telemetry over UDS. The certificate is issued from the same audit log.
Saves: Removes the dedicated bench step from the certification path.
Roadside service · operator
Drive-or-tow triage
Roadside call. The remote server reads ECU state, decides whether the vehicle can reach the next garage on its own or needs a tow. Dispatch matches the diagnosis.
Saves: Removes the unnecessary tow when the vehicle can self-recover.
Fleet inspector · third-party
Inspector mutualisation
City restricts heavy-truck entry but requires inspection. Errand operators connect a device on the truck; one technician inspects many vehicles from an office.
Saves: One technician covers a fleet — the on-site-inspector OPEX line collapses.
OEM · workshop network
J2534 passthrough to a remote bench
A dealer-tool session runs on a workshop laptop; the same gateway carries the SAE J2534 passthrough live to the vehicle bus. The vehicle stays in the field; the tool stays at the bench.
Saves: Removes the physical dispatch — the dealer tool reaches the bus through MOS4.
The wedge
Autonomous vs interactive — same bus, different decider.
Autonomous
Multi Stacks
The device decides what to ask the bus, on a schedule, against a standardised stack. The cloud receives structured signal data. Best for fleet-wide telemetry, predictive maintenance, ELD, compliance reporting.
See Multi Stacks →Interactive
Remote Diagnostic
The cloud opens a session and drives the bus live. A bot or an operator reads ECU state, resets DTCs (Diagnostic Trouble Codes), pushes calibrations, attests and reflashes firmware, then closes the session. Best for stalled-truck recovery, ECU reset, OEM diagnostic session, workshop remote-assist.
See the session lifecycle ↓Session lifecycle
Open. Drive. Close.
Sequence diagram. Cloud bot sends StartTunnel through the remote server. Device returns a signed Connected acknowledgement. In a loop, the cloud sends diagnostic requests over UDS, J1939, ISOBUS, or Modbus; the device pulls the message and drives the vehicle ECU; the ECU responds; the device publishes the response back through the remote server to the cloud. When done, the cloud sends StopTunnel; the device acknowledges and drains the connection.
sequenceDiagram
participant Cloud as Cloud bot
participant Server as Remote server
participant Device as MOS4 device
participant ECU as Vehicle ECU
Cloud->>Server: StartTunnel(config)
Server->>Device: deliver StartTunnel
Device->>Server: Connected (signed ack)
loop session
Cloud->>Server: Diagnostic request (UDS/J1939/ISOBUS/Modbus)
Server->>Device: pull message
Device->>ECU: drive bus
ECU-->>Device: response
Device->>Server: publish response
Server->>Cloud: deliver response
end
Cloud->>Server: StopTunnel
Server->>Device: deliver StopTunnel
Device->>Server: AckStop + drain One end-to-end tunnel per StartTunnel request. The session opens, drives the bus, completes the action, closes. TLS mutual authentication on the diagnostic tunnel. Per-action signed authorisation for any state-changing call.
What the bot can do
Four action classes. Each with its own safety boundary.
Read
Live UDS / J1939 / ISOBUS / Modbus reads, ECU fault-code dumps, parameter snapshots, frame captures.
Safety: Read-only path is unconditional. No write side-effects.
Reset
Clear DTCs, soft-reset ECU, reset learnt adaption values.
Safety: Per-action signed authorisation. Audit log records actor, time, action, target ECU.
Reconfigure
Push a calibration block, write to non-volatile storage, swap a feature flag at the ECU level.
Safety: Multi-party authorisation where the protocol requires it (UDS security-access). Rollback path mandatory.
Reflash
Push a new ECU firmware over the UDS programming session.
Safety: Attestation + signature verification on the device side before the bus session opens. Boot-count-based revert on failed reflash. Safety interlocks are not override-able from the Remote Diagnostic surface.
Why this matters
A truck roll becomes a packet.
For the subset of field failures that don't need a wrench — a wedged ECU, an out-of-spec calibration, a missed parameter — Remote Diagnostic resolves the call without dispatching a technician. The platform doesn't replace the workshop. It removes the workshop from the loop when the loop doesn't need the workshop.
Reference architecture
Cloud → tunnel → orchestrator → engine → bus.
Reference architecture flow. Cloud bot or operator initiates a signed TLS tunnel to the remote server. The tunnel feeds the Remote Diagnostic session orchestrator. The orchestrator gates every state-changing action behind per-action signed authorisation, multi-party where required. The gate hands off to the same engine that drives Multi Stacks — UDS, J1939, ISOBUS, Modbus, J2534-passthru. The engine talks to the vehicle bus. Every action is recorded in an audit log with per-action provenance, and the audit log is replayed back to the cloud.
flowchart LR Cloud[Cloud bot or operator] --> Tunnel[Signed TLS tunnel<br/>to the remote server] Tunnel --> Orch[RD session orchestrator<br/>Idle <-> InSession lifecycle] Orch --> Gate[Per-action signed authorisation<br/>multi-party where required] Gate --> Eng[Same engine as Multi Stacks<br/>UDS / J1939 / ISOBUS / Modbus / J2534-passthru] Eng --> Bus[Vehicle bus] Eng --> Audit[Audit log<br/>per-action provenance] Audit --> Cloud
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Is Remote Diagnostic a separate product or a built-in capability?
Built-in OS capability. Every MOS4 device exposes the Remote Diagnostic surface. No separate licence, no separate agent, no separate fleet-side install. Same OS image across modem-class, compute-class, and AI-class silicon tiers.
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What protocols are supported?
The same set the autonomous engine drives: UDS (ISO 14229), J1939, ISOBUS, Modbus, and SAE J2534 passthrough. Multi Stacks and Remote Diagnostic share the same engine; the difference is the mode of operation, not the protocol surface.
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Can the cloud bot brick a vehicle?
No. Safety interlocks are not override-able from the Remote Diagnostic surface. Reflash is signed and attested; the device verifies the signature before opening the UDS programming session. Bootcount-based revert restores the previous firmware on failed reflash. UDS security-access gating still applies per ECU.
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How is access to the session controlled?
TLS mutual authentication on the diagnostic tunnel — CA cert, client cert, client key delivered in the StartTunnel configuration and dropped at session end. StartTunnel itself is a signed Cloud Client request. Reset, Reconfigure, and Reflash actions each carry per-action signed authorisation. The audit log records actor, time, action, and target.
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What's the difference between Remote Diagnostic and Multi Stacks?
Mode of operation. Multi Stacks is autonomous: the device decides what to ask the bus on a schedule, and the cloud receives. Remote Diagnostic is interactive: the cloud opens a session, drives the bus live, and closes when done. Same engine, same protocols, same physical bus.
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Can dealer tools reach the vehicle through Remote Diagnostic?
Yes. SAE J2534 passthrough is supported. The dealer-tool session runs on a workshop laptop and reaches the vehicle bus through the same gateway and tunnel — no separate device, no physical dispatch.