U300B
Serious Severity (Level 4)Ignition Input Accessory/On/Start
OBD-II diagnostic trouble code U300Bindicates a fault detected by the vehicle's onboard computer. This code applies to all OBD-II compliant vehicles and should be addressed promptly to avoid potential engine or emissions system damage.
Severity Level 4 — Serious
This code indicates a serious issue that can cause noticeable driveability problems and potential engine damage if not addressed. The vehicle should be taken to a mechanic as soon as possible. Extended driving is not recommended.
Common Symptoms
- Multiple warning lights
- Gauges may not work
- Vehicle may not start
Possible Causes
- Ignition Input Accessory/On/Start
- Fault in related component or circuit
Common Fixes
- Scan with OBD2 diagnostic tool
- Inspect related components and wiring
Estimated Repair Cost
$200 – $1000(typical range; varies by vehicle make and model)
These are estimated costs based on generic repair data. Actual costs may vary depending on your vehicle, location, and labor rates.
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