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Here are the description and trouble shooting procedures.
DTC P0300 - RANDOM MISFIRE DETECTED
1. Connect external tachometer. Using scan tool in MUT II mode, read SERVICE DATA No. 22 (crankshaft position). Check engine RPM during cranking and at idle. If RPM displayed on scan tool and tachometer are equal, go to next step. If RPM displayed on scan tool and tachometer are not equal, go to step 4).
2. Using oscilloscope, perform crankshaft position sensor wave form check. Connect Test Harness MD998478 between Crankshaft Position (CKP) sensor and harness connector. Connect analyzer special patterns pickup to CKP sensor terminal No. 2. If test harness is not available, connect analyzer special patterns pickup to PCM terminal No. 89 (Blue/White
wire) Go to next step.
3. With engine idle speed stable, compare CKP sensor wave pattern to standard wave pattern. If wave pattern is okay, go to step 5). If wave pattern is not okay, go to next step.
4. Check CKP sensor connector, PCM connector and wiring harness between PCM and CKP sensor connector. Check CKP sensor and sensing plate for proper installation. If wiring, connectors and sensor installation are okay, replace CKP sensor.
5. Start and warm engine. Turn all accessories off. Increase engine speed to 2500 RPM. Using scan tool in MUT II mode, read SERVICE DATA No. 81 (long-term fuel compensation). If fuel trim is -12.5-12.5 percent (during closed loop), go to next step. If fuel trim is not as specified, check fuel trim fault.
6. Using scan tool in MUT II mode, read SERVICE DATA No. 21 (engine coolant temperature). If temperature displayed on scan tool is equal to actual Engine Coolant Temperature (ECT), go to next step. If temperature displayed on scan tool is not equal to
actual ECT, check ECT circuit.
7. Check ignition coil, spark plugs, spark plug wires and compression pressure.
Monday, April 5th, 2010 AT 11:27 AM