P0302

Wiring Diagram:

CIRCUIT DESCRIPTION
ECM monitors crankshaft revolution speed and engine speed via the crankshaft position sensor and cylinder No. via the camshaft position sensor. Then it calculates the change in the crankshaft revolution speed and from how many times such change occurred in every 200 or 1000 engine revolutions, it detects occurrence of misfire. When ECM detests a misfire (misfire rate per 200 revolutions) which can cause overheat and damage to the three way catalytic converter, it makes the malfunction indicator lamp (MIL) flash as long as misfire occurs at that rate. After that, however, when the misfire rate drops, MIL remains ON until it has been judged as normal 3 times under the same driving conditions.

Also, when ECM detects a misfire (misfire rate per 1000 revolutions) which will not cause damage to three way catalytic converter but can cause exhaust emission to be deteriorated, it makes MIL light according to the 2 driving cycle detection logic.

Detecting Condition / Possible Cause:

DTC CONFIRMATION PROCEDURE

NOTE: Among different types of random misfire, if misfire occurs at cylinders 1 and 4 or at cylinders 3 and 2 simultaneously, it may not possible to reconfirm DTC by using the following DTC confirmation procedure. When diagnosing the trouble of DTC P0300 (Random misfire detected) of the engine which is apparently misfiring, even if DTC P0300 cannot be reconfirmed by using the following DTC confirmation procedure, proceed to the following Diag. Flow Table.

WARNING:
- When performing a road test, select a place where there is no traffic or possibility of a traffic accident and be very careful during testing to avoid occurrence of an accident.
- Road test should be carried out with 2 persons, a driver and a tester.




1. Turn ignition switch OFF.
2. Clear DTC with ignition switch ON.

3. Check vehicle and environmental condition for:
- Indication of fuel level meter in combination meter: 1/4 or more (For 1999 MY)
- Altitude (barometric pressure): 2400 m, 8000 ft or less (560 mmHg, 75 kPa or more)
- Ambient temp.: -10 °C, 14 °F or higher
- Intake airtemp.: 70 °C, 158 °F or lower
- Engine coolant temp.: -10 - 110 °C, 14 - 230 °F.

4. Start engine and keep it at idle for 2 min. or more.
5. Check DTC in "DTC" mode and pending DTC in "ON BOARD TEST" or "PENDING DTC" mode.
6. If DTC is not detected at idle, consult usual driving based on information obtained in "Customer complaint analysis" and "Freeze frame data check".

Inspection (Steps 1 - 6):

Inspection (Steps 7 - 11):

Figure 1, 2, 3, 4, 5, 6, 7 For Steps 3, 4, 5 And 7: