Ignition Input Signal Mismatch
The U300E code indicates a discrepancy in the ignition input signal received by the control module. According to SAE J2012, this code sets when the control module detects that the ignition signal remains continuously active (ON) or its state does not match the expected operating condition of the vehicle. The system monitors the ignition circuit to ensure the module correctly receives information about whether the vehicle is in the ignition-on or ignition-off position, which is critical for managing multiple vehicle functions.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Faulty ignition switch
- Damaged or corroded wiring in the ignition signal circuit
- Loose or corroded connectors in the control module harness
- Internal failure of the control module (ECU/PCM/BCM)
- Defective fuse in the ignition circuit
- Short to voltage in the ignition signal circuit
3. Symptoms You Will Notice
- Engine may not start or may stall
- Electrical accessories may not function properly
4. Step-by-Step Diagnosis
Check for blown fuses in the ignition circuit and replace if necessary.
Inspect the ignition switch for proper operation and continuity.
Visually examine wiring and connectors for damage, corrosion, or looseness.
Test the ignition signal circuit for shorts or opens using a multimeter.
If all else is normal, suspect a faulty control module and perform module-specific tests.
5. Frequently Asked Questions
Is it safe to drive?▼
It is not recommended to drive with this code as it may cause stalling or no-start conditions, leading to unsafe driving situations.
How much does it cost to fix?▼
Repair costs typically range from $100 to $500, depending on the root cause (e.g., ignition switch replacement vs. control module replacement).