Overview
A machine staying locked is usually the platform doing its job — the diagnostic skill is telling correct locks from stuck ones quickly. Work this in order; each step is fast.
1. Is the lock correct?
Five legitimate reasons a machine is locked, each with its own tell:
| Reason | Tell | The fix |
|---|---|---|
| No current pre-start | The app offers Start pre-start | Do the pre-start — that's the product |
| The last check expired | The pre-start timer ran out; red solid LED | Fresh pre-start |
| Key off too long, or a power cycle | The app offers Confirm and unlock | Confirm in the app, if nothing has changed since the last pre-start |
| The check was invalidated | You received an invalidation notification | Fresh pre-start |
| Out of service | The app shows the out-of-service banner on the machine | Fix the blocking defect, then close it if a critical item that failed on a pre-start or a service checklist locked the machine, or have the flag lifted if a technician set it — see Defect Management Workflow |
Out of service: the lockout names the blocking defect
If any of these is the story, the machine is behaving. Everything below is for when they aren't.
2. The pre-start passed but the unlock step failed
The inspection is recorded — you're retrying only the Bluetooth unlock, from the result screen:
- In range? Stand at the machine, near where the Interlock is mounted. See Bluetooth Connection Issues.
- Interlock powered? An Interlock fed from the ignition circuit runs only with the key on — turn the key, then Retry. A dark LED means no power at all.
- Someone else connected? Blue solid LED means another phone holds the Interlock's single connection.
The result screen, where the unlock is its own step after the check is submitted
3. "Not licensed" where the unlock should be
Your licence for this machine's group is missing or expired — the app enforces it at the moment of unlock, offline included. The machine stays visible with a renew prompt when it's expiry. Your admin fixes this in minutes: Licensing Operators.
No active licence: the app says so before you reach a machine
4. First time on this machine, offline
The very first unlock of a machine on a given phone needs one online moment (the phone fetches that machine's key; after that it's cached). No coverage + never-connected = told to go online. See Working Offline.
5. The machine cranks but won't start — and the Interlock says unlocked
Green solid LED but no start is usually not the interlock — the Interlock's relay is closed, and the machine's own systems (fuel, battery, isolators, its own safety interlocks) are the suspects. The Interlock can only hold one circuit open; it can't cause faults elsewhere.
6. Device-level checks (Technician)
- LED dark — the Interlock has no power. A dead Interlock leaves the machine startable (Fail-START); if the machine also won't start, the problem is the machine, not the Interlock.
- Amber flashing — hardware fault; connecting with the app triggers recovery. Persistent faults: support with the
D-serial. - Wiring — a machine that won't crank even with the Interlock unlocked (or fuse-pulled) points at the installation: verify against the installation guide's verification list.
The genuine emergency
A machine that must move now with no working unlock path: the 10-second hold on the Interlock's mode button toggles a time-limited bypass — the deliberate last resort, not a workaround. Unlike the in-app bypass, it records no person and PreStartGo never receives a record of it. See Emergency Bypass.
Troubleshooting
| Symptom | Most likely | Jump to |
|---|---|---|
| App says a pre-start is needed | It is — that's the gate | Step 1 |
| Passed, unlock step spins/fails | BLE — range, power, or a second phone | Step 2 |
| "Not licensed" | Licence lapsed or wrong group | Step 3 |
| Offline and it wants a connection | First-ever unlock on this phone | Step 4 |
| Green LED, machine still won't start | The machine itself | Step 5 |
| Red LED that shouldn't be, everything checked | Device/wiring | Step 6, then support with the D- serial |