BMW P0307: Cylinder 7 Misfire Detected — Diagnosis and Repair

P0307 means Cylinder 7 Misfire Detected. The DME records it when crankshaft acceleration identifies repeated combustion loss on cylinder 7; diagnosis must separate an electrical signal fault from a real system fault. Use OBDThink to preserve the recording module and freeze frame for P0307, then test cylinder 7 ignition, injection and mechanical sealing without guessing or swapping parts. What Does P0307 Mean? This standardized powertrain DTC concerns cylinder 7 ignition, injection and mechanical sealing. On BMW vehicles the exact test plan and component layout vary by engine, chassis and DME software, so verify the VIN in BMW service information. The decisive clue is not the code alone: crankshaft acceleration identifies repeated combustion loss on cylinder 7. Compare commanded behavior with the measured signal before condemning a component. Code: P0307 Definition: Cylinder 7 Misfire Detected Module: DME (gasoline) or DDE where applicable Key evidence: crankshaft acceleration identifies repeated combustion loss on cylinder 7 Typical causes: worn plug, failed coil, injector fault, intake leak at runner 7, low compression, or valve-train defect Severity: diagnose promptly Note: confirm engine and wiring variant by VIN First preserve the freeze frame. If crankshaft acceleration identifies repeated combustion loss on cylinder 7, inspect cylinder 7 ignition, injection and mechanical sealing and its supporting system in the same operating condition. Symptoms • Cylinder 7 Misfire Detected commonly appears with extended cranking, intermittent stalling, timing retard or cylinder-specific combustion roughness. • The freeze frame may show the fault while crankshaft acceleration identifies repeated combustion loss on cylinder 7, which is more useful than the warning lamp alone. • Target and actual values separate a persistent defect from an intermittent connector or harness interruption. • A companion fault from the same module may identify whether cylinder 7 ignition, injection and mechanical sealing is the cause or a consequence. Possible Causes Start with accessible circuit and connection checks, then prove the sensor or actuator, and leave expensive mechanical work until last. • Low cost: inspect the connector, terminal tension, contamination and the harness around cylinder 7 ignition, injection and mechanical sealing. • Low cost: check hoses, ducts, grounds, fuses and supply paths that directly affect cylinder 7 ignition, injection and mechanical sealing. • Medium cost: test the named sensor or actuator dynamically; the defining evidence is that crankshaft acceleration identifies repeated combustion loss on cylinder 7. • Medium cost: correct the system condition rather than masking it; likely branches include worn plug, failed coil, injector fault, intake leak at runner 7, low compression, or valve-train defect. • High cost: only after circuit and mechanical evidence, consider control-unit repair or major mechanical work using VIN-specific BMW service data. Diagnosis Steps with OBDThink OBDThink is an independent BMW coding and diagnostic mobile app and is not affiliated with BMW AG. Available live data and freeze frame detail depend on the vehicle, adapter and module. • 1. Scan every control unit with OBDThink; save P0307, the recording DME, status, frequency and freeze frame before clearing anything. • 2. Reproduce the recorded operating condition safely and graph target versus actual values. Correlate engine-speed or cam/knock data with starting and load; inspect the named sensor, shielded harness and mechanical trigger. • 3. With ignition safely isolated where required, inspect and electrically test cylinder 7 ignition, injection and mechanical sealing; load-test power and ground rather than relying on continuity alone. • 4. Separate circuit from mechanism: manipulate the harness while monitoring data, then perform the relevant smoke, vacuum, pressure, airflow or waveform test. • 5. Confirm the repair by clearing the code, completing a cold start and controlled drive cycle, and rescanning all related modules. IF crankshaft acceleration identifies repeated combustion loss on cylinder 7 AND wiring/load test fails -> repair the circuit ELSE IF command is correct but mechanism does not respond -> test cylinder 7 ignition, injection and mechanical sealing ELSE compare companion faults and BMW VIN-specific test plan THEN clear, drive, and rescan The fastest distinction is to watch the relevant command and actual value while testing cylinder 7 ignition, injection and mechanical sealing; a fixed signal and a responding mechanism point in different directions. Repair • Low cost: Restore the cheapest verified defect around cylinder 7 ignition, injection and mechanical sealing, such as a loose pin, damaged insulation, contaminated connection or directly related hose. • Medium cost: Repair the specific system fault that makes crankshaft acceleration identifies repeated combustion loss on cylinder 7; likely paths to prove are worn plug, failed coil, injector fault, intake leak at runner 7, low compression, or valve-train defect. • Medium cost: Service or replace the named element of cylinder 7 ignition, injection and mechanical sealing when live data changes correctly during a substitute or bidirectional functional check. • High cost: Authorize control-unit or internal mechanical work only with VIN-matched wiring, waveform and BMW test-plan evidence; coding is not a substitute for repair. After repair, verify that crankshaft acceleration identifies repeated combustion loss on cylinder 7 no longer occurs, readiness can complete, and P0307 does not return as pending or confirmed. Can You Drive with P0307? Avoid continued driving if stalling, hard starting, metallic noise or severe misfire occurs. Treat P0307 as measured evidence, not a parts order. A saved freeze frame, a target/actual comparison and a load-tested circuit usually reveal the least expensive correct repair.