AutoCodes – Generic – U300C

U300C Code - Ignition Input Off/On/Start

Quick Answer

The Powertrain Control Module (PCM) monitors the ignition key state. Common causes include Ignition Input Off/On/Start (ISP-R) harness is open or shorted, Ignition Input Off/On/Start (ISP-R) circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: U300C indicates Ignition Input Off/On/Start.
Common causes: Common causes include Ignition Input Off/On/Start (ISP-R) harness is open or shorted, Ignition Input Off/On/Start (ISP-R) circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 4,065

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jun 18, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code U300C Description

The Powertrain Control Module (PCM) monitors the ignition key state. The U300C code sets when the key state is not available.

OBDII Code U300C - Ignition Input Off/On/Start - AutoCodes.com — U300C Code - Ignition Input Off/On/Start

What does this mean?

What are the Possible Causes of the DTC U300C?

Ignition Input Off/On/Start (ISP-R) harness is open or shorted
Ignition Input Off/On/Start (ISP-R) circuit poor electrical connection

How to Fix the DTC U300C?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U300C code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the U300C code?

Need more information on how to fix the U300C code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U300C code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U300C Ford — Ignition Input Off/On/Start
U300C Mercury — Ignition Input Off/On/Start

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about U300C Code

1. What does the OBDII code U300C mean?

The U300C code indicates an issue with the ignition input signal, specifically during the Off, On, or Start positions.

2. What are the common symptoms of the U300C code?

Symptoms may include the engine not starting, intermittent power loss, dashboard warning lights, or accessories not functioning properly.

3. What causes the U300C code to appear?

Common causes include a faulty ignition switch, damaged wiring or connectors, a malfunctioning Body Control Module (BCM), or low battery voltage.

4. Can a weak battery trigger the U300C code?

Yes, a weak or failing battery can cause voltage irregularities, leading to the U300C code.

5. How do I diagnose the U300C code?

Start by checking the battery voltage, inspecting the ignition switch and related wiring for damage, and scanning the BCM for additional trouble codes.

6. Can I drive my car with the U300C code?

Driving with the U300C code is not recommended, as it may cause starting issues or unexpected electrical failures.

7. How do I fix the U300C code?

Repairs may involve replacing a faulty ignition switch, repairing damaged wiring, cleaning corroded connectors, or reprogramming the BCM.

8. How much does it cost to fix the U300C code?

Repair costs vary depending on the issue but typically range from $100 to $500, including parts and labor.

9. Can the U300C code clear itself?

The code may clear temporarily if the issue is intermittent, but it will likely return until the underlying problem is resolved.

10. Do I need professional help to fix the U300C code?

If you're experienced with electrical diagnostics, you may handle minor repairs. However, complex issues like BCM reprogramming typically require professional assistance.