DTC Detection Logic
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the crankshaft position (CKP) sensor (POS) signal to vary, ECM can determine that a misfire is occurring.
| Sensor | Input signal to ECM | ECM function |
|---|---|---|
| Crankshaft position sensor (POS) | Engine speed | On board diagnosis of misfire |
The misfire detection logic consists of the following two conditions.
- One Trip Detection Logic (Three Way Catalyst Damage)
On the 1st trip, when a misfire condition occurs that can damage the three way catalyst (TWC) due to overheating, the MIL will blink.
When a misfire condition occurs, the ECM monitors the CKP sensor signal every 200 engine revolutions for a change.
When the misfire condition decreases to a level that will not damage the TWC, the MIL will turn off.
If another misfire condition occurs that can damage the TWC on a second trip, the MIL will blink.
When the misfire condition decreases to a level that will not damage the TWC, the MIL will remain on.
If another misfire condition occurs that can damage the TWC, the MIL will begin to blink again.
- Two Trip Detection Logic (Exhaust quality deterioration)
For misfire conditions that will not damage the TWC (but will affect vehicle emissions), the MIL will only light when the misfire is detected on a second trip. During this condition, the ECM monitors the CKP sensor signal every 1, 000 engine revolutions.
A misfire malfunction can be detected on any one cylinder or on multiple cylinders.
DTC DETECTING CONDITION AND POSSIBLE CAUSEDTC No. Trouble diagnosis name DTC detecting condition Possible cause P0300 Multiple cylinder misfire detected Multiple cylinders misfire. - Improper spark plug
- Insufficient compression
- Incorrect fuel pressure
- The fuel injector circuit is open or shorted
- Fuel injector
- Intake air leak
- The ignition signal circuit is open or shorted
- Lack of fuel
- Signal plate
- A/F sensor 1
- Incorrect PCV hose connection
P0301 No. 1 cylinder misfire detected No. 1 cylinder misfires. P0302 No. 2 cylinder misfire detected No. 2 cylinder misfires. P0303 No. 3 cylinder misfire detected No. 3 cylinder misfires. P0304 No. 4 cylinder misfire detected No. 4 cylinder misfires.