U300B: The ignition input signal for accessory, on and start positions has a fault
The ignition input signal for accessory, on and start positions has a fault. Check the switch, connector and wiring.
| Code | U300B |
|---|---|
| System | Communication network |
| Group | U30xx, Communication network |
| Type | Generic: it means the same on every make |
How to read and clear U300B 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 U300B with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
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
- U3007 The control unit input power B is not working properly
- U3008 The control unit ground A is not working properly
- U3009 The control unit ground B is not working properly
- U300A The ignition switch is not working properly
- U300C The ignition input signal for off, on and start positions has a fault
- U300D The ignition input signal for on and start positions has a fault
- U300E The ignition input signal has a fault in the on position
- U300F The ignition input accessory is not working properly
What does code U300B mean?
The ignition input signal for accessory, on and start positions has a fault. Check the switch, connector and wiring.
How do you clear U300B?
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, U300B 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.
