P0866: The gearbox control unit communication gives a higher signal than normal
The gearbox control unit communication gives a higher signal than normal. It is usually the part, its wiring or a connector with poor contact.
| Code | P0866 |
|---|---|
| System | Engine and transmission |
| Group | P08xx, Transmission |
| Type | Generic: it means the same on every make |
How to read and clear P0866 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0866 with its description and whether it’s confirmed, pending or permanent.
This code is usually stored by the gearbox control unit. If the car reports it over standard OBD, you read it for nothing with FREE; to read it straight from the gearbox control unit, with its description and clearing, you need PRO.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P0862 The gear shift module communication gives a higher signal than normal
- P0863 The gearbox control unit communication has an electrical fault
- P0864 The gearbox control unit communication gives readings outside the normal range
- P0865 The gearbox control unit communication gives a lower signal than normal
- P0867 There is a fault in the gearbox oil pressure
- P0868 Transmission fluid pressure low
- P0869 The gearbox oil pressure is above normal
- P086A The neutral position sensor A has a broken or disconnected wire
- P0841 Transmission fluid pressure sensor/switch A: circuit range or performance
- P0842 Transmission fluid pressure sensor/switch A: circuit low
- P0843 Transmission fluid pressure sensor/switch A: circuit high
What does code P0866 mean?
The gearbox control unit communication gives a higher signal than normal. It is usually the part, its wiring or a connector with poor contact.
How do you clear P0866?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0866 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
