U300B
Ignition Input Accessory/On/Start
U300B is an OBD-II diagnostic trouble code meaning: Ignition Input Accessory/On/Start. Common causes: faulty ignition switch, open or short circuit in the circuit. Estimated repair cost: $17–89.
Symptoms
- Problems starting the engine
- Accessories not working in ACC position
- Unstable operation of the ignition system
- The warning light on the dashboard is on
- No power in ON position
Causes
- Faulty ignition switch
- Open or short circuit in the circuit
- Problems with the ignition relay
- Control module malfunction
- Corrosion of contacts or connectors
How to Fix
- Check the ignition switch for damage
- Diagnose the ignition signal circuit for opens and short circuits
- Check contacts and connectors in the circuit
- Test the ignition relay
- Read fault codes in other modules
Related codes
Error U300B by Vehicle Brand
FAQ
What does the U300B code mean?
U300B is an OBD-II diagnostic trouble code that indicates: Ignition Input Accessory/On/Start
What causes a U300B error code?
The most common causes of U300B include: Faulty ignition switch; Open or short circuit in the circuit; Problems with the ignition relay; Control module malfunction.
How do I fix a U300B diagnostic trouble code?
To fix U300B: Check the ignition switch for damage. Diagnose the ignition signal circuit for opens and short circuits. Check contacts and connectors in the circuit. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with U300B?
Yes, but get it checked soon
How much does it cost to fix U300B?
The estimated repair cost for U300B is $17–89. Actual cost depends on your vehicle, location, and labor rates.
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