Suzuki 2000 Grand Vitara SQ625 Service Manual page 72

6-68 ENGINE DIAGNOSIS (G16 / J20 ENGINES)
DTC P0300 RANDOM MISFIRE DETECTED
DTC P0301 CYLINDER 1 MISFIRE DETECTED
DTC P0302 CYLINDER 2 MISFIRE DETECTED
DTC P0303 CYLINDER 3 MISFIRE DETECTED
DTC P0304 CYLINDER 4 MISFIRE DETECTED
SYSTEM DESCRIPTION
ECM (PCM) measures the angle speed of the crankshaft based on the pulse signal from the CKP sensor and CMP
sensor for each cylinder. If it detects a large change in the angle speed of the crankshaft, it concludes occurrence
of a misfire. When the number of misfire is counted by the ECM (PCM) beyond the DTC detecting condition, it deter-
mines the cylinder where the misfire occurred and outputs it as DTC.
DTC DETECTING CONDITION AND TROUBLE AREA
DTC DETECTING CONDITION
D Misfire which causes catalyst to overheat
during 200 engine revolutions is detected
at 2 or more cylinders. (MIL flashes as long
as this misfire occurs continuously.)
D Misfire which affects exhaust emission
adversely during 1000 engine revolutions is
detected at 2 or more cylinders
(2 driving cycles detection logic)
D Misfire which causes catalyst to overheat
during 200 engine revolutions is detected
at 1 cylinder. (MIL flashes as long as this
misfire occurs continuously.)
D Misfire which affects exhaust emission
adversely during 1000 engine revolutions is
detected at 1 cylinder
(2 driving cycles detection logic)
DTC CONFIRMATION PROCEDURE
WARNING:
D 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.
D Road test should be carried out with 2 persons, a driver and a tester, on a level road.
NOTE:
Check to make sure that the following conditions are satisfied when using this DTC CONFIRMATION PRO-
CEDURE.
D Intake air temp.: –8 – 70_C (18 – 158_F)
D Engine coolant temp.: –8_C, 18_F or higher
D Altitude (barometric pressure): 2400 m, 8000 ft or less (560 mmHg, 75 kPa or more)
1) Connect scan tool to DLC with ignition switch OFF.
2) Turn ON ignition switch and clear DTC, pending DTC and freeze frame data by using scan tool and start engine.
3) Increase vehicle speed to speed recorded as freeze frame data (V) + 5 km/h when detecting misfire.
4) Keep driving above vehicle speed for 5 min.
5) Stop vehicle and check DTC (or pending DTC) by using scan tool.
TROUBLE AREA
D Ignition system
D Fuel injector and its circuit
D Fuel line pressure
D Engine compression
D Abnormal air drawn in
D EGR system
D Fuel level sensor
D Valve clearance (valve lash adjuster)
D Valve timing