Misfire Detection Monitor

DTC P0300, P0301, P302, P0303, P0304, P0305, P0306 DETECTION CONDITION AND POSSIBLE CAUSE

DTC P0300, P0301, P302, P0303, P0304, P0305, P0306	MISFIRE DETECTION MONITOR
DETECTION CONDITION	P0300 indicates multiple cylinders are misfiring or the PCM cannot identify which cylinder is misfiring. P0301 through P0306 indicates random misfire detected or cylinder 1, 2, 3, 4, 5, or 6 misfire detected.
POSSIBLE CAUSE	Ignition system. Fuel injectors. Fuel pressure. Evaporative Emission system. Base engine. Running out of fuel. Camshaft Position (CMP) sensor. Stuck open EGR Valve.
HINT	Refer to MISFIRE DETECTION MONITOR
Courtesy of MAZDA MOTORS CORP.

DTC P0300, P0301, P302, P0303, P0304, P0305, P0306 INSPECTION

STEP	INSPECTION		ACTION
1	Was PCM Quick Test performed?	Yes	If any other DTCs are present, go to appropriate pinpoint test. For DTC P0300 only, go to step 18. Otherwise, go to next step.
1	Was PCM Quick Test performed?	No	Perform PCM Quick Test.
2	CHECK/COMPARE PID VALUES Accessories off (A/C, heater, etc.). Key ON, Engine OFF (KOEO). Access DPFEGR PID with the NGS Tester and record values. Key ON, Engine Running (KOER). Compare KOEO and KOER PID values. Key OFF. Calculate the difference (KOER value - KOEO value). Is the difference within 0.15 V?	Yes	Go to step 4.
2		No	Go to next step.
3	CHECK OPERATION OF EGR VALVE NOTE: Perform KOER Self Test and repair any DTCs before proceeding with this test. The symptom indicates possible EGR flow at idle with no EGR DTCs output. Possible causes: EGR valve not fully seating. EGR vacuum regulator solenoid vent restricted. Damaged EGR vacuum regulator solenoid. Disconnect vacuum hose at EGR valve and plug hose. Access DPFEGR PID with a NGS Tester and note voltage. Key ON, Engine Running (KOER). With engine at idle, look at the DPFEGR PID voltage and compare to the engine off reading. An increase in the voltage at idle indicates that the DPFEGR sensor is sensing EGR flow. Key OFF. Was the DPFEGR PID voltage greater at idle by a minimum of 0.15 V than with the engine off?	Yes	The DPFEGR PID voltage is indicating EGR flow at idle. Since the EGR vacuum hose is disconnected and plugged, the fault is most likely in the EGR valve. Remove and inspect the EGR valve for signs of contamination, unusual wear, carbon deposits, binding and other damage. Repair or replace as necessary. Go to step 22.
3		No	This indicates a fault in the EGR valve vacuum supply. Inspect the EGR vacuum regulator (EGRVR) solenoid vent and vent filter for restrictions. Repair as necessary. If OK, replace EGRVR solenoid. See ELECTRICAL COMPONENT LOCATOR . Go to step 20.
4	CHECK FUEL PRESSURE WARNING: The fuel system will remain pressurized when the engine is not running. To prevent injury or fire, use caution when working on the fuel system. Install fuel pressure gauge. Key ON, Engine Running (KOER). Note fuel pressure. Increase engine speed to 2, 500 rpm and maintain for 1 minute. Note and compare fuel pressure. Key OFF. Was fuel pressure between 30--65 psi (207--448 kPa) and did it remain at specification within 5 psi (16.5 kPa) for 60 seconds?	Yes	Go to next step.
4		No	See TEST 5: FUEL DELIVERY SYSTEM .
5	CHECK INJECTOR DRIVER PIDS INJ1F THROUGH INJ6F Key ON, Engine OFF (KOEO). Access appropriate PID(s) for the suspect fuel injector. Is the PID status Yes?	Yes	Go to next step.
5		No	Go to step 9.
6	CHECK RESISTANCE OF FUEL INJECTOR(S) AND HARNESS Disconnect PCM. Install Breakout Box, leave PCM disconnected. Measure resistance of INJ circuit between PCM test pin 71 or 97 and the fuel injector harness connector. Is the resistance between 11.0 and 18.0 ohms?	Yes	Replace PCM. See COMPUTERIZED ENGINE CONTROLS . Go to step 20.
6		No	Go to next step.
7	CHECK RESISTANCE OF FUEL INJECTOR HARNESS Disconnect harness connector at suspected fuel injector. Measure resistance of VPWR circuit between PCM test pin 71 and the fuel injector harness connector. Measure resistance of INJ circuit between appropriate PCM test pin and the suspect fuel injector test pin. INJ1F: test pin 75 INJ2F: test pin 101 INJ3F: test pin 74 INJ4F: test pin 100 INJ5F: test pin 73 INJ6F: test pin 99 Is each resistance less than 5.0 ohms?	Yes	Go to next step.
7		No	Repair open circuit. Go to step 20.
8	CHECK FUEL INJECTOR HARNESS CIRCUIT FOR SHORT TO POWER OR GROUND Measure resistance between PCM test pin 71 (VPWR) and suspect fuel injection SIG circuit PCM test pin(s). Measure resistance between PCM test pin and 103 (PWR GND) and suspect fuel injector SIG circuit PCM test pin(s). Is each resistance greater 10K ohms?	Yes	Go to next step.
8		No	Repair short circuit. Go to step 20.
9	INSPECT FUEL INJECTOR OPERATION Remove fuel injector from suspected cylinder. Swap suspected fuel injector with a fuel injector from another cylinder. Key ON, Engine Running (KOER). Does misfire DTC move to cylinder with suspected injector?	Yes	Replace fuel injector. See FUEL RAILS & INJECTORS in REMOVAL, OVERHAUL, AND INSTALLATION article in Engine Performance . Go to step 20.
9		No	Go to next step.
10	CHECK VACUUM SYSTEM NOTE: Some vacuum leaks can be heard. Inspect all vacuum lines for damage, such as pinched lines, cracks, proper routing and assembly. Is the vehicle vacuum system OK?	Yes	Go to next step.
10		No	Repair the vacuum system. Go to step 20.
11	CHECK DAMPER AND PULLEY ASSEMBLY CAUTION: Remove the front cover if necessary to observe the crankshaft pulley. Observe the crankshaft pulley for wobble. Examine the pulse ring fastened to the harmonic damper. Does the crankshaft pulley wobble or is the pulse ring loose or damaged?	Yes	Disconnect battery for 5 minutes to allow PCM to learn new data, due to the old pulse ring. Replace the pulley or damper assembly. Go to step 20.
11		No	Go to next step.
12	CHECK EVAPORATIVE EMISSION SYSTEM NOTE: The Misfire Monitor can be influenced by the Evaporative Emission (EVAP) System. The next five test steps will diagnose the EVAP System. Check the evaporative emissions canister for fuel saturation. Is there an excess amount of liquid fuel present in the evaporative emissions canister?	Yes	Replace evaporative emissions canister. Go to step 20.
12		No	Check fuel tank vent system. Go to next step.
13	PRESSURE TEST EVAPORATIVE EMISSION SYSTEM Perform EVAP Emission System Leak Test. See EVAPORATIVE EMISSION SYSTEM LEAK TEST . Is EVAP system holding pressure?	Yes	Go to next step.
13		No	Repair as necessary. Go to step 20.
14	CHECK VACUUM IN EVAPORATIVE EMISSION SYSTEM Check for blockage/restrictions or cut hoses between engine vacuum port and EVAP canister. Check for blockage in fuel tank vent system. Is fault indicated?	Yes	Replace damaged vacuum hoses or remove blockage/restrictions. Go to step 20.
14		No	Go to next step.
15	CHECK FOR EVAPORATIVE EMISSION PURGE VALVE HOUSING LEAKS Connect EVAP purge valve. Install a hand vacuum pump to the fuel vapor port of the EVAP canister on the EVAP canister purge solenoid vacuum line. Apply 53 kPa (16 in-Hg) of vacuum with the vacuum pump. Does the EVAP canister purge solenoid hold vacuum at room temperature?	Yes	Go to next step.
15		No	Remove vacuum pump. Replace EVAP canister purge solenoid. See ELECTRICAL COMPONENT LOCATOR . Go to step 20.
16	CHECK FOR FILTER CONTAMINATION OR DAMAGE ON EVAPORATIVE EMISSION PURGE VALVE Remove vacuum line from input port to intake manifold on EVAP canister purge solenoid (control vacuum solenoid part of the valve). Install a hand held vacuum pump to the open input vacuum port on the EVAP canister purge solenoid. Apply 48--52 kPa (10--15 in-Hg) of vacuum to the EVAP canister purge solenoid. Does the EVAP canister purge solenoid hold vacuum or is the valve very slow to release vacuum to atmosphere?	Yes	Service EVAP canister purge solenoid filter. If unable to clean filter or remove blockage, replace the EVAP canister purge solenoid. Go to step 20.
16		No	Remove vacuum pump. Reconnect all components. Go to next step.
17	CHECK FOR BASE ENGINE CONCERNS NOTE: This step will determine if there are any base engine concerns that may have caused the misfire DTC or drive concern. Perform the following tests in order to evaluate base engine integrity. Perform an Engine Compression test. Perform Valve Train analysis. Check PCV system. Check possible leakage points. See ENGINE COMPONENT TESTS , for all of the above. Is any service required?	Yes	Service as necessary. Go to step 20.
17		No	The fault that caused the misfire DTC is an intermittent. See TEST 4: INTERMITTENT .
18	CHECK/COMPARE PID VALUES Accessories off (A/C, heater, etc.). Key ON, Engine OFF (KOEO). Access DPFEGR PID with the NGS Tester and record values. Key ON, Engine Running (KOER). Compare Key ON, Engine OFF (KOEO) and KOER PID values. Key OFF. Does KOEO = KOER +/- 0.15 within the specification of 0.2-1.3?	Yes	Disconnect NGS Tester. Go to next step.
18		No	Go to step 20.
19	CHECK CMP SENSOR OUTPUT Disconnect PCM. Install Breakout Box, PCM connected. Set multimeter on AC scale (monitor less than 5.0 volts). Measure voltage between PCM test pin 85 (CID) and PCM test pins 51, 103 (PWR GND) while running the engine at varying rpm. Does AC voltage vary greater than 0.1 V?	Yes	Verify CMP sensor is installed correctly. See IGNITION SYSTEM . If CMP is installed correctly, replace PCM. See COMPUTERIZED ENGINE CONTROLS . Go to step 20.
19		No	Replace CMP sensor. See IGNITION SYSTEM . Go to step 20.
20	DRIVE CYCLE Make sure to reconnect all disconnected connectors. Clear DTCs from PCM memory using NGS tester generic OBD-II function. Perform Misfire Monitor Drive Cycle. See DRIVE CYCLES . Retrieve pending code. Is same DTC present?	Yes	Replace PCM. See COMPUTERIZED ENGINE CONTROLS . Go to next step.
20		No	Go to next step.
21	VERIFY TROUBLESHOOTING OF DTCs COMPLETED Perform PCM Quick Test. Is any DTC present?	Yes	Go to applicable DTC inspection.
21		No	Troubleshooting complete.