DTC P0303: CYLINDER #3 MIS-FIRE Dodge Ram Wagon B1500

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For circuit identification and wiring diagram, see RAM VAN & RAM WAGON wiring diagram in WIRING DIAGRAMS article.

Note. DTC P0303: CYLINDER #3 MIS-FIRE is monitored with engine running, after successfully performing Crankshaft Position (CKP) sensor learn procedure. DTC may be stored in Powertrain Control Module (PCM) when PCM senses more than 2 percent misfire rate is measured during 2 trips or with a 10-30 percent misfire rate during one trip. Possible causes are: misfire does not return, defective Camshaft Position (CMP) or CKP sensor, improper valve timing, vacuum leak, defective ignition system, engine mechanical problem, fuel contamination, improper fuel pressure or capacity, or defective fuel pump.

1. Turn ignition on, with engine off. Using scan tool, read DTCs. If MIS-FIRE GOOD TRIP COUNTER is displayed and displayed count is "0", go to next step. If MIS-FIRE GOOD TRIP COUNTER is not displayed or displayed count is not "0", go to step 3).
2. At this time, conditions required to set DTC are present. Using scan tool, read and record FREEZE FRAME and SIMILAR CONDITIONS data. Operate vehicle using data in SIMILAR CONDITIONS. While in SIMILAR CONDITIONS screen, go to WHICH CYLINDER IS MIS-FIRING monitor. If scan tool is not counting misfires at this time, go to next step. If scan tool is counting misfires at this time, go to step 4).
3. At this time, engine misfire does not exist or is an intermittent problem. Using scan tool, read and record FREEZE FRAME and SIMILAR CONDITIONS data. Road test vehicle under conditions in FREEZE FRAME and SIMILAR CONDITIONS data, paying particular attention to fault setting conditions such as speed, temperature, load and MAP vacuum. Using scan tool, read DTCs. If DTC P0303: CYLINDER #3 MIS-FIRE returns, go to next step. If DTC P0303 CYLINDER #3 MIS-FIRE does not return, see «INACTIVE DTC CONDITION»(ref-139160-S32382818132002042600000) . Test is complete.
4. Using scan tool, read and record FREEZE FRAME data. Using freeze frame data, attempt to determine cause of misfire. If adaptive fuel percentages are -15 to 15 percent, go to next step. If adaptive fuel percentages are not -15 to 15 percent, go to step 10).
5. Check for contaminated fuel. Replace fuel and clean fuel system as necessary. Perform TEST VER-5A2. If fuel is okay, go to next step.
6. Perform fuel pressure leak-down test. See «FUEL PRESSURE LEAKDOWN TEST»(ref-555-S20556543212002042600000) under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES - TRUCKS & RWD VANS - GASOLINE article. If fuel pressure leak-down test passes, go to next step. If fuel pressure leak-down test does not pass, repair fuel system as necessary. Perform TEST VER-5A2.
7. Perform fuel pump amperage test. See «FUEL PUMP AMPERAGE TEST»(ref-555-S17306562852002042600000) under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES - TRUCKS & RWD VANS - GASOLINE article. If fuel pump amperage test passes, go to next step. If fuel pump amperage test does not pass, repair fuel system as necessary. Perform TEST VER-5A2.
8. Perform fuel pump capacity test. See «FUEL PUMP CAPACITY TEST»(ref-555-S26455266782002042600000) under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES - TRUCKS & RWD VANS - GASOLINE article. If fuel pump capacity test passes, go to next step. If fuel pump capacity test does not pass, repair fuel system as necessary. Perform TEST VER-5A2.
9. Perform fuel pump pressure test. See «FUEL PRESSURE TEST»(ref-555-S29372960852000030800000) under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES - TRUCKS & RWD VANS - GASOLINE article. If fuel pump pressure test passes, test is complete. If fuel pump pressure test does not pass, repair fuel system as necessary. Perform TEST VER-5A2.
10. Using scan tool, read and record FREEZE FRAME and LOAD VALUE data. Using freeze frame data, attempt to determine cause of misfire. If load value is more than 50 percent and engine coolant temperature is within normal operating range, go to next step. If load value is 50 percent or less, and/or engine coolant temperature is not within normal operating range, go to step 14). NOTE: Refer to manufacturer's operation manual for instructions in use of engine analyzer.
11. Ensure engine is off. Connect engine analyzer to engine. Start engine and allow it to idle. If engine will not idle, maintain constant engine speed at more than idle. Set engine analyzer to read display or parade pattern. Remove any spark plug wire while observing secondary kV line. If secondary voltage is at least 25,000 volts, go to next step. If secondary voltage is not at least 25,000 volts, replace ignition coil. Perform TEST VER-5A2. NOTE: Refer to manufacturer's operation manual for pattern analysis procedure.
12. Ensure engine is off. Ensure engine analyzer is still connected to engine. Start engine and allow it to idle. If engine will not idle, maintain constant engine speed at more than idle. Set engine analyzer to read display or parade pattern. Check secondary ignition pattern. If secondary ignition pattern is okay, go to next step. If secondary ignition pattern is not okay, repair indicated secondary ignition system component as necessary. Perform TEST VER-5A2.
13. Check the following additional items as possible mechanical problems: Engine Vacuum Must Be At Least 13" In Neutral Engine Valve Timing Must Be Within Specification Engine Compression Must Be Within Specification Engine Exhaust System Must Be Free Of Restrictions Engine PCV System Must Flow Freely Engine Drive Sprockets Must Be Properly Positioned Torque Converter Stall Speed Must Be Within Specification Power Brake Booster Must Have No Internal Leaks Fuel Must Be Free Of Contamination Fuel Injectors Must Be Free Of Restrictions Fuel Injector Control Wires Must Be Installed On Correct Injector Repair mechanical problems as necessary. Perform TEST VER-5A2. If no mechanical problems exist, test is complete.
14. Using scan tool, read and record FREEZE FRAME and ENGINE RPM data. Using freeze frame data, attempt to determine cause of misfire. If engine speed is less than 3000 RPM and engine coolant temperature is not within normal range, go to next step. If engine speed is more than 3000 RPM and engine coolant temperature is within normal operating range, use lab scope to test CMP and CKP sensors, and check valve timing and engine vacuum. Perform TEST VER-5A2.
15. Check following items for possible causes of cylinder misfire: Injector Harness Connectors Ignition Coil Circuit Spark Plugs Engine Mechanical Problem PCM Power Grounds Irregular CMP Sensor Signal Irregular CKP Sensor Signal Fuel Injectors Restricted Exhaust Intake Restriction PCM EVAP System EGR System Damaged Trigger Wheel Accessory Drive Belts If any listed possible cause exists, repair as necessary. Perform TEST VER-5A2. If no listed possible cause exists, test is complete.