OBD Guide

U300F

Ignition Input Accessory

U300F is an OBD-II diagnostic trouble code meaning: Ignition Input Accessory. Common causes: ignition switch malfunction, damage to the ignition relay. Estimated repair cost: $17–89.

Severity
⚠️ Medium
Can you drive?
Do not drive — repair immediately
Approx. repair cost
$17–89 (est.)

Symptoms

  • Car won't start in ACC position
  • Problems with the operation of accessories when the ignition is on
  • Dashboard flashing or turning off
  • Unstable operation of electrical equipment

Causes

  • Ignition switch malfunction
  • Damage to the ignition relay
  • Open or short circuit in the circuit
  • Problems with the engine control unit
  • Contact corrosion

How to Fix

  1. Check the condition of the ignition switch
  2. Diagnose the ignition relay
  3. Check the integrity of wiring and connections
  4. Scan the control unit for other errors
  5. Replace faulty components

Related codes

Error U300F by Vehicle Brand

FAQ

What does the U300F code mean?

U300F is an OBD-II diagnostic trouble code that indicates: Ignition Input Accessory

What causes a U300F error code?

The most common causes of U300F include: Ignition switch malfunction; Damage to the ignition relay; Open or short circuit in the circuit; Problems with the engine control unit.

How do I fix a U300F diagnostic trouble code?

To fix U300F: Check the condition of the ignition switch. Diagnose the ignition relay. Check the integrity of wiring and connections. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with U300F?

Do not drive — repair immediately

How much does it cost to fix U300F?

The estimated repair cost for U300F is $17–89. Actual cost depends on your vehicle, location, and labor rates.

See also: Russian version · NationStat