AutoCodes – Mitsubishi – P0172 Mitsubishi

P0172 Mitsubishi Code - System Too Rich- Cylinders 1-4

Quick Answer

With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. Common causes include Faulty Front Heated Oxygen Sensor, Faulty Spark Plugs, Faulty Mass Air Flow (MAF) sensor. 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: P0172 Mitsubishi indicates System Too Rich- Cylinders 1-4.
Common causes: Common causes include Faulty Front Heated Oxygen Sensor, Faulty Spark Plugs, Faulty Mass Air Flow (MAF) sensor.
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.

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Code Popularity 20,663

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 May 02, 2020

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0172 Mitsubishi Description

With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. The Engine Control Module (ECM) calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.
In case the amount of the compensation value is extremely large (The actual mixture ratio is too lean.), the ECM judges the condition as the fuel injection system malfunction and light up the MIL (2 trip detection logic).

OBDII Code P0172 Mitsubishi - System Too Rich- Cylinders 1-4 - AutoCodes.com — P0172 Mitsubishi Code - System Too Rich- Cylinders 1-4

What does this mean?

What are the Possible Causes of the DTC P0172 Mitsubishi?

Faulty Front Heated Oxygen Sensor
Faulty Spark Plugs
Faulty Mass Air Flow (MAF) sensor
Exhaust Gas Leaks
Ignition Misfiring
Incorrect Fuel Pressure
Faulty Fuel Injectors

How to Fix the DTC P0172 Mitsubishi?

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 P0172 Mitsubishi 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 P0172 Mitsubishi code?

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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 P0172 Mitsubishi Code

1. What are the common symptoms of OBDII code P0172 in a Mitsubishi indicating a rich fuel mixture in cylinders 1-4?

Symptoms may include decreased fuel efficiency, black smoke from the exhaust, rough idling, and a strong smell of gasoline.

2. What are the possible causes of OBDII code P0172 in a Mitsubishi?

Potential causes include a faulty oxygen sensor, clogged fuel injectors, a malfunctioning mass airflow sensor, a vacuum leak, or issues with the fuel pressure regulator.

3. How can I diagnose the source of OBDII code P0172 in my Mitsubishi?

To pinpoint the issue, you can perform a thorough inspection of the oxygen sensor, check for any vacuum leaks, test the fuel pressure, clean or replace the fuel injectors, and ensure the mass airflow sensor is functioning correctly.

4. What steps can I take to repair OBDII code P0172 in a Mitsubishi?

Repair options may include replacing a faulty oxygen sensor, cleaning or replacing clogged fuel injectors, fixing any vacuum leaks, repairing or replacing the mass airflow sensor, or addressing issues with the fuel pressure regulator.

5. Is it safe to continue driving my Mitsubishi with OBDII code P0172 present?

It is not recommended to drive your vehicle with a rich fuel mixture, as it can lead to engine damage over time and potentially cause other issues. It's best to address the problem promptly.

6. Can a dirty air filter cause OBDII code P0172 in a Mitsubishi?

Yes, a dirty air filter can disrupt the air-fuel mixture ratio and potentially contribute to a rich condition in cylinders 1-4, triggering OBDII code P0172.

7. Will resetting the OBDII code P0172 in my Mitsubishi make the issue go away?

Resetting the code may temporarily turn off the check engine light, but it will not fix the underlying problem causing the rich fuel mixture. The issue should be diagnosed and repaired to prevent further complications.

8. How often should I check and replace the oxygen sensor in my Mitsubishi to prevent OBDII code P0172?

It is recommended to inspect and replace the oxygen sensor as part of regular maintenance, typically every 60,000 to 90,000 miles, to help prevent issues like OBDII code P0172.

9. Can a failed catalytic converter cause OBDII code P0172 in a Mitsubishi?

A failing catalytic converter can potentially cause a rich fuel mixture by restricting exhaust flow, but it is not a common direct cause of OBDII code P0172 related to cylinders 1-4.