Code P0300: Random Misfire Detected
NOTE:
For component terminal identification, see TERMINAL IDENTIFICATION
in this article. For appropriate WIRING DIAGRAMS, see WIRING DIAGRAMS
section.
- Connect external tachometer. Using scan tool, read SERVICE DATA No. 22 (crankshaft position sensor). Check engine RPM during cranking and at idle. If RPM displayed on scan tool and tachometer are the same, go to next step. If RPM displayed on scan tool and tachometer are not the same, go to step 4 .
- Using oscilloscope, perform crankshaft position sensor wave form check. Connect test harness (MD998478) between crankshaft position sensor and harness connector. Connect analyzer special patterns pickup to crankshaft position sensor terminal No. 2. If test harness is not available, connect analyzer special patterns pickup to PCM terminal No. 89 (Blue/White wire).
- With engine idle speed stable, compare crankshaft position sensor wave form to standard wave form. See Fig 1 . If wave form is okay, go to step 5 . If wave form is not okay, go to next step.
- Check crankshaft position sensor connector, PCM connector and wiring harness between PCM and crankshaft position sensor connector. Check crankshaft position sensor and sensing plate for proper installation. If wiring, connectors and sensor installation are okay, replace crankshaft position sensor.
- Start and warm engine. Turn all accessories off. Increase engine speed to 2500 RPM. Read SERVICE DATA No. 81 (long-term fuel compensation). If fuel trim is -12.5 to +12.5 percent (during closed loop), go to next step. If fuel trim is less than -12.5 or more than +12.5 percent (during closed loop), check fuel trim fault. See CODE P0170: FUEL TRIM FAULT .
- Read SERVICE DATA No. 21 (coolant temperature sensor). If temperature displayed on scan tool is equal to actual coolant temperature, go to next step. If temperature displayed on scan tool is not equal to actual coolant temperature, check coolant temperature circuit. See CODE P0115: COOLANT TEMPERATURE CIRCUIT FAULT .
- Check ignition coil, spark plugs, spark plug wires and compression pressure. See BASIC TESTING - 2.0L TURBO article.