The Check Engine Light – More than You Wanted to Know
Check Engine Light.
The check engine light comes on when the vehicles On Board Diagnostic system detects an abnormal reading from one of the various sensors. In more advanced vehicles, it can also come on when other non-engine sub-system malfunctions are detected. When the light comes on, the computer system will have likely stored a diagnostic code that our technicians can read using one of our scan tools to review the error data and diagnose the problem.
Doesn’t the computer tell you what’s wrong?
The quick answer is No, and it’s a common misconception. The computer can only detect that a particular sensor or sensors has provided data that is outside of the predetermined expected readings of that / those sensors. In many cases it can show the technician the conditions in which the error occurred, but not WHY it occurred. It takes a specially trained technician to review the available data and then inspect those systems to determine why the malfunction is occurring, and what is likely to return that sub-system to its normal performance.
Why is my Check Engine light flashing?
The check engine light will flash when it detects a problem with the engine that may cause damage to parts of the emission system, such as the catalytic converters. This is typically due to an engine misfire or other condition where unburnt fuel works its way out of the engine and down to the converters. This causes the converters to overheat making them ineffective and possibly damaged requiring an expensive replacement. Under these conditions it is strongly advised that you stop driving the vehicle as soon as it is safe to do so.
Other systems lights.
Along with the check engine light you may also have other lights come on as well. It is very common that some systems such as vehicle stability control or the cruise control will be disabled by the main computer as they require a fully functioning engine system. Yet other system lights such as ABS (Antilock Braking system) or SRS (Supplementary Restraint System) indicate errors with those systems and are not related to engine performance. And don’t forget, lights for engine oil pressure or temperature still indicate what they have always indicated, and are not usually replaced by the simple Check Engine light.
Why so many sensors?
Todays highly computerized engines provide fantastic power and reliability while being much more fuel efficient. This is because we now use computers and sensors to replace many of the intricate moving parts of the early combustion engine:
- Distributor cap, rotor, points, condenser and wires have been replaced by a crankshaft position sensor and individual coils for each spark plug.
- The carburetor has been replaced by fuel injectors and oxygen sensors.
- Camshaft position sensors and variable timing solenoids provide many adjustments per second to achieve better power and fuel economy.
The Diagnostic Process.
When our technicians inspect your vehicle, the first thing we will do is scan the vehicles computer system for codes. The codes will describe the errors found in the various vehicle sub-systems. Our technicians will then inspect those various sub-systems for problems that need to be repaired. Sometimes the problems are obvious. Other times, there can be several issues that can cause similar codes, and each will need to be inspected prior to providing a full and comprehensive diagnosis.