U300A

Ignition Switch

Moderate severity

The control module detects an inconsistent or implausible ignition switch state — multiple positions reported simultaneously, or the position contradicts other inputs.

Common causes

Ignition switch contacts worn
One of the most commonly reported causes for this code — check this first.
high
Typical part cost: $70-440
Gateway module routing CAN messages incorrectly
Less common, but worth ruling out after the more likely causes.
low
Typical part cost: $70-440
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First things to check

1Confirm the code with a scan tool and check for additional related codes.
2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.

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Related codes

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Frequently asked questions

What does U300A mean?

U300A means "Ignition Switch". It is a generic OBD-II code that points to a fault in the network / communication.

What are the most common causes of U300A?

ignition switch contacts worn; gateway module routing can messages incorrectly; can terminating resistor (120 ω) drifted out of spec — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.

Can I keep driving with this code?

The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical. Use the Wrenchify app for a full diagnosis specific to your vehicle.

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