What Does Pending Mean on a Car Diagnostic Test? Understanding Pending Codes

When you use a car diagnostic tool, such as an auto scan tool, you might come across different types of diagnostic codes. Among these, “pending codes” can be a bit confusing. Understanding What Does Pending Mean On A Car Diagnostic Test is crucial for effective vehicle maintenance. These codes, along with stored and permanent codes, are your car’s way of communicating potential issues related to engine performance and emissions.

In this article, we’ll dive deep into pending codes, explaining what they are, why they appear, and what you should do when you see them. We’ll also compare them to stored and permanent codes to give you a complete picture of your vehicle’s diagnostic health.

Decoding Diagnostic Trouble Codes: Pending, Stored, and Permanent

Your vehicle’s On-Board Diagnostics system, or OBD, is like a doctor for your car. It continuously monitors various systems and components. When it detects an issue, it generates a Diagnostic Trouble Code (DTC). These DTCs are categorized into three main types: Pending Codes, Stored Codes, and Permanent Codes. Each type provides different information about the nature and severity of the problem.

What are Pending Codes? The Early Warning Signs

Pending codes are essentially the OBD system’s early warnings. They are DTCs that have been detected but not yet verified as a persistent problem. Think of them as preliminary fault indicators. When you see a pending code, it means your vehicle has sensed something is amiss, but it needs more confirmation before escalating it to a more serious alert, like turning on the check engine light.

Temporary and Unconfirmed: Pending codes are temporary by nature. They indicate an issue that has occurred but hasn’t consistently repeated itself over multiple driving cycles.
Recent Issue Detection: These codes often appear after a recent event, such as a slight sensor malfunction or a minor deviation in system readings.
Awaiting Confirmation: The OBD system requires further monitoring and observation under specific driving conditions to confirm if the fault is real and persistent enough to become a stored code.

Let’s look at some practical examples to better understand what does pending mean on a car diagnostic test in real-world scenarios.

Real-World Examples of Pending Codes

Oxygen Sensor Hiccups (DTC P0131): Imagine an oxygen sensor that’s momentarily giving erratic readings. This might trigger a pending code like P0131, which indicates “O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1).” The system isn’t sure if the sensor is truly failing or if it was just a temporary glitch. It will continue to monitor the sensor to see if the low voltage reading persists.
EVAP System Minor Leaks (DTC P0456): A very small leak in the evaporative emissions control system might trigger a pending code P0456, signaling a “Small Evap Leak.” The system needs to perform more tests over subsequent drive cycles to confirm if this small leak is consistent enough to be a real problem.
Mass Airflow Sensor Inconsistencies (DTC P0101): If the mass airflow sensor provides readings that are slightly out of the expected range, it could lead to a pending code P0101, indicating “Mass Air Flow Circuit Range/Performance Problem.” The vehicle’s computer needs to observe this sensor’s behavior over time to determine if the inconsistency is a recurring issue or just a one-time anomaly.

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Stored Codes: Confirmed Problems Triggering the Check Engine Light

Stored codes are the next level of DTCs. These are confirmed issues that the OBD system has verified as persistent problems. Unlike pending codes, stored codes mean the fault has been detected consistently over multiple monitoring cycles and has met the criteria to illuminate the check engine light on your dashboard.

Verified and Persistent Issues: Stored codes represent faults that are no longer considered temporary. The OBD system has confirmed their continuous presence.
Check Engine Light Activation: When a code becomes stored, it usually triggers the check engine light, immediately alerting the driver to a problem that needs attention.
Action Required: Stored codes indicate that something is definitely wrong and requires diagnosis and repair. Ignoring stored codes can lead to more serious issues and potential damage.

Examples of Stored Codes Demanding Attention

Catalytic Converter Inefficiency (DTC P0420): A stored code like P0420, “Catalyst System Efficiency Below Threshold (Bank 1),” indicates a confirmed problem with the catalytic converter’s performance. This usually means the catalytic converter is not cleaning emissions effectively and needs inspection or replacement.
Oxygen Sensor Slow Response (DTC P0138): If an oxygen sensor is consistently slow in responding to changes in the exhaust gas mixture, a stored code P0138, “O2 Sensor Circuit High Voltage (Bank 1 Sensor 2),” may appear. This signifies a persistent issue with the sensor or its circuitry, requiring diagnostic checks and potential sensor replacement.
Fuel System Running Rich (DTC P0172): A stored code P0172, “System Too Rich (Bank 1),” confirms that the engine’s fuel system is consistently delivering too much fuel. This can lead to reduced fuel economy, poor engine performance, and potential damage to the catalytic converter if not addressed.

Permanent Codes: The Unforgettable Fault Markers

Permanent codes are a special type of DTC introduced to ensure emissions system repairs are properly verified. They are unique because they cannot be cleared by simply using a scan tool or disconnecting the battery. Permanent codes remain in the system until the underlying issue is completely resolved and the OBD system confirms the fix through specific drive cycles.

Non-Erasable Faults: Permanent codes are designed to stay put. They cannot be cleared using standard methods, ensuring that emissions-related problems are properly fixed.
Emissions Test Significance: These codes are particularly important for emissions testing. The presence of permanent codes can lead to an automatic failure in emissions inspections, as they indicate unresolved issues that could affect emissions.
Post-Repair Verification: After repairs are made, the vehicle must be driven under specific conditions to allow the OBD monitors to run and confirm the repair. Only after successful monitor completion will the permanent code clear itself.

Practical Examples of Permanent Codes and Their Implications

Oxygen Sensor Malfunction (DTC P0133): A permanent code like P0133, “O2 Sensor Circuit Slow Response (Bank 1 Sensor 1),” in permanent form, indicates a persistent oxygen sensor issue that has not been resolved through previous repairs or code clearing attempts. The sensor must be properly repaired or replaced for this code to disappear.
Evaporative Emission Control System Leak (DTC P0442): A permanent code P0442, “Evaporative Emission Control System Leak Detected (Small Leak),” signifies that a small leak in the EVAP system continues to exist even after potential fixes. Thorough diagnostic checks are needed to find and repair the leak to clear this code.
Catalytic Converter Damage (DTC P0421): This permanent code, P0421, “Warm Up Catalyst System Efficiency Below Threshold (Bank 1),” indicates a confirmed failure in the catalytic converter’s efficiency that persists. Repair, likely replacement of the catalytic converter, is necessary before this code will clear.

Can Pending Codes Turn into Stored or Permanent Codes?

Yes, pending codes can absolutely evolve into stored or even permanent codes. Understanding what does pending mean on a car diagnostic test is just the first step. Here’s how the progression typically happens:

From Pending to Stored: If the issue that triggered a pending code continues to occur during subsequent driving cycles, the OBD system will verify the fault. Once verified, the pending code will be promoted to a stored code, and the check engine light will likely illuminate. This transition signifies that the initial temporary issue has become a confirmed, persistent problem.
Stored Codes and Permanent Codes: In the case of emissions-related issues, a stored code, if not addressed and repaired, can eventually lead to a permanent code, especially in newer vehicles. Permanent codes are specifically related to emissions systems and are designed to ensure these systems are properly repaired for environmental compliance.

It’s important to address pending codes as early warnings. Ignoring them can lead to the problem worsening, turning into a stored code, and potentially causing more damage and expensive repairs down the road. Moreover, letting an emissions-related pending code become permanent can cause issues with vehicle inspections and compliance.

What Should You Do When You See a Pending Code?

Seeing a pending code when you run a car diagnostic test might seem less urgent than a stored code with a check engine light, but it still warrants attention. Here’s a recommended course of action:

Note the Code: Record the specific pending code number and description. This information will be crucial for further diagnosis if the code persists or escalates.
Research the Code: Use online resources or repair manuals to understand what the pending code means specifically for your vehicle make and model. This will give you a better idea of the potential issue and its severity.
Monitor the Code: Since pending codes are temporary, monitor if the code turns into a stored code, especially if the check engine light comes on. Use your bluetooth obd2 reader to periodically re-scan for codes over a few driving cycles.
Consider a Professional Check-up: If the pending code persists, turns into a stored code, or if you notice any drivability issues, it’s wise to take your vehicle to a professional mechanic. Early diagnosis can prevent minor issues from becoming major, costly repairs.
Avoid Clearing Pending Codes Immediately: While you can clear pending codes with an OBD2 scanner, it’s generally not recommended to do so right away, especially if you are not familiar with car repairs. Clearing the code without understanding and fixing the underlying issue is like silencing an alarm without addressing the fire. Let the code remain for a while to see if it escalates or resolves itself. If you do clear it, monitor if it reappears.

Understanding what does pending mean on a car diagnostic test empowers you to take proactive steps in vehicle maintenance. Pending codes are your car’s subtle cry for help, and responding to them promptly can save you time, money, and potential breakdowns.

Conclusion: Proactive Diagnostics with Pending Codes

Pending codes are a valuable feature of your vehicle’s diagnostic system. They offer an early peek into potential problems, allowing you to address minor issues before they escalate into major repairs. By understanding what does pending mean on a car diagnostic test, you can use this information to your advantage, ensuring your vehicle remains in optimal condition.

Whether you are using a basic car reader or a best professional obd2 scanner like those from ANCEL, paying attention to all types of diagnostic codes, including pending codes, is key to maintaining your vehicle’s health and performance. Regularly scanning your vehicle for codes and understanding their implications is a smart practice for every car owner.

FAQs About Pending Codes

Will a pending code always turn into a stored code?

Not always. Sometimes a pending code can disappear on its own if the issue was temporary or intermittent. However, it’s essential to monitor pending codes because they can often become stored codes if the underlying problem persists.

Can I pass an emissions test with pending codes?

It depends on local regulations. In some areas, vehicles with pending codes may still pass emissions tests, while in others, they might fail or require further inspection. It’s best to check your local emissions testing guidelines. Generally, it’s advisable to resolve any pending codes before an emissions test to ensure compliance.

Is it safe to drive with a pending code?

Usually, yes, it is generally safe to drive with a pending code, as it indicates an issue that is not yet confirmed as critical. However, it’s wise to investigate the code and monitor your vehicle’s performance. If you notice any unusual symptoms like reduced power, strange noises, or poor fuel economy, it’s best to get your vehicle checked by a professional promptly, even if it’s just a pending code.

How do I clear pending codes?

Pending codes can be cleared using an OBD2 scanner. Simply connect the scanner to your vehicle’s diagnostic port, navigate to the codes section, and select the option to clear codes. However, remember that clearing a code does not fix the underlying problem. If the issue persists, the pending code or a stored code will likely reappear.

Should I be concerned about a pending code if the check engine light is not on?

Yes, you should still be aware of a pending code even if the check engine light is off. A pending code is an early warning sign. Addressing the issue at this stage can prevent it from becoming a more serious problem that triggers the check engine light and potentially leads to more extensive damage.