Can a misfire be detected in an OBD II engine?
One very important point to keep in mind about OBD II misfire detection is that the system does not tell you why the engine is misfiring. OBD II can give you an exact count of the misfires cylinder by cylinder (which you can find in Mode $06 with a scan tool), but it can’t tell you what’s causing the misfires.
When does the Check Engine light go on after a misfire?
In most cases, a misfire problem will set a pending code on the first trip, but won’t turn on the check engine light or set a hard code until the second trip if the misfire problem continues.
What causes the engine warning light to pop?
Engine warning light: if your car develops a misfire as a result of bad Injectors, lousy spark plugs, low fuel pressure, or any other causes, it will cause the warning light to pop in the dashboard. Check light indicates problems in the engine system.
Can a crank sensor be used to detect misfires?
One of the drawbacks of using a crank sensor to detect misfires is that it can sometimes be fooled by normal powertrain vibrations. Driving on a rough road, for example, may produce variations in crank speed that seem like misfires but are not.
What does a misfire code on a check engine light mean?
Misfires that turn on the check engine light and log a cylinder-specific fault code are the easiest to diagnose. The OBD II system will identify the cylinder (s) that are not contributing their normal dose of power and set a code that corresponds to the firing order. A P0303 code, for example, would tell you that the No. 3 cylinder is misfiring.
What does a flashing check engine light mean?
A flashing check engine light and a P0301 to P0312 diagnostic trouble code (DTC) is a surefire indication that one or more cylinders are misfiring. Occasional misfires may pass unnoticed, but a steady misfire is hard to miss. The engine usually feels rough, lacks power and uses more gas than usual. Sometimes a misfire may feel like a vibration.
How does the PCM work to diagnose a misfire?
This greatly helps the Powertrain Control Module (PCM–car computer) calculate crankshaft acceleration time. The PCM can detect when a cylinder decelerates (an indication of a misfire), store a Diagnostic Trouble Code (DTC) in memory, and turn on the Check Engine Light.
Do you scan your memory for engine misfires?
Not all misfires are directly translated into DTCs, especially intermittent ones. Yet, it’s a good idea to scan your computer memory because other potential stored codes may help you in diagnosing and fixing your engine misfires (see the box below on Misfire-Related DTCs).