Will a Blown Head Gasket Throw a Code?
A blown head gasket may not always trigger a check engine light or throw a diagnostic trouble code (DTC) on its own. However, it can pave the way for symptoms that do lead to the generation of codes. In this article, we will explore the potential codes that may arise due to a blown head gasket and how to diagnose this critical issue.
Understanding Potential Diagnostic Trouble Codes (DTCs)
When a head gasket blows, several issues can develop that may trigger diagnostic trouble codes. These codes are generated based on sensor readings and engine performance. Here are some codes that might appear as a result of a blown head gasket:
Coolant Leaks
If a blown head gasket leads to coolant leaking into the combustion chamber, it can cause misfires that will trigger codes such as P0300 Random/Multiple Cylinder Misfire Detected. Misfires can disrupt the engine's overall performance and efficiency, leading to these diagnostic codes.
Overheating
A blown head gasket can lead to an overheated engine. The engine temperature may rise, potentially triggering a code related to engine temperature, such as P0128 Coolant Temperature Sensor Range/Performance. Overheating can also lead to a loss of coolant, which may cause the engine to continue running hot, increasing the risk of further engine damage.
Exhaust Gas in Coolant
When exhaust gases enter the coolant system, it can affect sensor readings. This can lead to codes related to the oxygen sensors or fuel trim systems, such as P0171 Lean Fuel Condition or P0174 Lean Fuel Condition (Bank 2). These codes indicate issues with the engine's emissions and fuel management systems.
Oil Contamination
Oil and coolant mixing can cause problems in the engine's oil pressure system, leading to codes related to oil pressure or engine performance. For example, you might see P0307 Crankshaft Position Sensor Circuit Failure or P0308 Crankshaft Position Sensor Circuit Malfunction. These codes indicate that the engine's sensors are malfunctioning or failing to provide accurate readings.
Athlete Against the Computer
While it’s true that a blown head gasket might not directly throw a code associated with it, the resulting issues often will. If you suspect a blown head gasket, a thorough diagnostic check is crucial. You may receive an engine misfire code for the affected cylinders, and if it's severe enough, you might also receive a mass airflow sensor code if air has been introduced from the metered side of the mass airflow sensor. This can affect the mass airflow sensor's reporting signal, leading to further diagnostics and codes.
While diagnostic software can help identify issues, it is often wiser to rely on physical symptoms and diagnostic checks. A diagnostic system with cylinder head temperature sensors may eventually alert you to a blown head gasket, but the warning may come too late to prevent engine damage. Software depends on hardware to function, and a human brain is necessary to understand and interpret the information correctly. Physical probing for head gasket symptoms remains the best method for accurate diagnosis.
Takeaway: Rely on your diagnostic skills and physical checks rather than solely relying on diagnostic software to catch the subtleties of a blown head gasket. Trust your instincts and use the tools available to you to ensure your engine's health.
Do not guess. Invest in a block leak test from Amazon and perform a self-diagnostic check to confirm the presence of a blown head gasket before it's too late.