08 Service
Troubleshooting
No USB, no RPM, no start, no idle, and the first five logs to take.
9 min readUpdated 2026-08
No USB
- Charge-only cable on the case USB-C. Try another data cable.
- TunerStudio already owns the port — close it before the console.
- Laptop charger ground loop — unplug the charger.
- ECU stuck in DFU (Device Manager shows STM32 BOOTLOADER). Finish the flash or power-cycle out of BOOT0.
- Firmware crashed. DFU recover. See Firmware update.
No RPM while cranking
- Composite logger is empty: sensor power, air gap, wiring. A VR with 3 mm of air gap will be silent at cranking speeds.
- Logger has teeth, RPM is 0: wrong trigger type. 60-2 decoded as 36-1 will not sync.
- Logger looks inverted: swap VR polarity.
- RPM spikes to thousands: noise. Re-route, shield, keep coils away, check sensor ground.
Cranks, no start
| Symptom | Look at |
|---|---|
| RPM good, no injector PW | Fuel cut, flood-clear (TPS high), req-fuel zero, pump output not assigned |
| PW present, no smell of fuel | Pump relay, fuse, dead low-side, injectors still on 12 V only (open ECU pin) |
| Fuel smell, no spark on light | Logic coil 12 V, coil ground, ignition output assignment, spark cut |
| Pops in the intake | Trigger offset 180° out, or coil 1 on the wrong cylinder |
| Pops in the exhaust, won’t catch | Too lean cranking, or wasted-spark pairing wrong |
Runs, badly
- Surging idle: idle PID, vacuum leak, TPS not actually closed, CLT lying.
- Lean in boost only: fuel pressure falling (pump, filter, regulator), not VE.
- Rich everywhere: req-fuel / dead-time, or a MAP transfer that reads low.
- Timing walks with RPM: VR polarity or a slipping damper — not the spark table.