P0301
DTC P0301 - CYLINDER 1 MISFIRE DETECTEDOUTLINE OF DIAGNOSIS
Detect whether the misfire occurred or not. (Revolution fluctuation method)
Monitoring the misfire which influences exhaust deterioration (5 times of FTP) and catalyst damage is made obligatory by the law. Misfire affecting these two has three patterns below.
- Intermittent misfire (The same cylinder misfires in random, or different cylinders misfire in random.): FTP 5 times misfire
- Every time misfire (The same cylinder misfires every time.): FTP 5 times misfire, Catalyst damage misfire.
The following detecting methods are adopted for these detection.
1. Intermittent misfire: FTP 5 times misfire
- 180° Interval Difference Method (MT: 1,800 rpm or less; AT: None)
- 360° Interval Difference Method (whole range)
- 720° Interval Difference Method (3,000 rpm or less)
2. Every time misfire: FTP 5 times misfire, Catalyst damage misfire
- 360° Interval Difference Method
ENABLE CONDITION
GENERAL DRIVING CYCLE
- Detecting misfire is carried out in the condition between idling and high revolution.
- Perform the diagnosis continuously.
DIAGNOSTIC METHOD
When the misfire occurred, the engine speed is decreased and the crankshaft position speed will change. Calculate the interval difference value (diagnostic value) from crankshaft position speed by the following formula, and judge whether the misfire occurs or not comparing the calculated result with judgment value. Counting the number of misfire up, and if the misfire ratio is higher during 1000 rev. or 200 rev., judge NG for the corresponding cylinder.
As the following figure, pick out a random cylinder as the standard and name it omg 0. And the former crankshaft position speed is named omg 1, the second former crankshaft position speed is named omg 2, the third is named omg 3, and the following is the same.
- 180° Interval Difference Method
Diagnosis value domg 180 = (omg - 1 omg 0) - (omg 7 - omg 1 )/6 Judge misfire occurs in the following cases.
- domg 180 > judgment value of positive side
- domg 180 > judgment value of negative side (judgment value before 180 °CA)
- 360° Interval Difference Method
Diagnosis value domg 360 = (omg 1 - omg 0) - (omg 4 - omg 3) Misfire judgment domg 360 > judgment value -> Misfire occurs
- 720° Interval Difference Method
Diagnosis value domg 720 = (omg 1 - omg 0) - (omg 7 - omg 6) Misfire judgment domg 720 > judgment value -> Misfire occurs
- FTP 1.5 times misfire (Misfire occurrence level affecting exhaust gas)
Judgment Value (Judge that malfunction occurs when the misfire ratio is high in 1000 engine revs.)
Time Needed for Diagnosis: 1000 engine revs.
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.
- Catalyst damage misfire (Misfire occurrence level damaging catalyst)
Judgment Value (Judge that malfunction occurs when the misfire ratio is high in 200 engine revs. (400 ignitions))
Map 1 Fault criteria threshold for misfire which would result in catalyst damage
These figures mean the misfire ratio (%) in 400 ignitions; for example, 22.5 (%) means 400 (ignition) x 22.5 (%) 90 (ignition) or more, so this case is judged misfire.
Time Needed for Diagnosis: 200 engine revs.
Malfunction Indicator Light Illumination: Illuminates as soon as the malfunction occurs.
DTC CLEAR CONDITION
- When the OK idling cycle was completed 40 times in a row
- When "Clear Memory" was performed
MALFUNCTION INDICATOR LIGHT CLEAR CONDITION
- When the similar driving cycle was completed 3 times in a row
- When "Clear Memory" was performed
FAIL SAFE
None
ECM OPERATING AT DTC SETTING
Memorize the freeze frame data. (For test mode $02)