BMW P0203: Injector Circuit/Open Cylinder 3 — Diagnosis and Repair

P0203 means Injector Circuit/Open Cylinder 3. The DME records it when the commanded cylinder 3 injection event has an open or implausible electrical load; diagnosis must prove the named circuit or mechanism before parts are replaced. Use OBDThink to preserve the recording module and freeze frame for P0203, then test cylinder 3 injector power feed, connector and DME low-side driver in the condition that set the fault. What Does P0203 Mean? This standardized powertrain DTC concerns cylinder 3 injector power feed, connector and DME low-side driver. BMW component location and test routing vary by engine, chassis and DME software; use the VIN-specific wiring diagram and service plan. The code is not a parts verdict. Its defining evidence is that the commanded cylinder 3 injection event has an open or implausible electrical load, so compare command, actual response and electrical integrity in the same operating window. Code: P0203 Definition: Injector Circuit/Open Cylinder 3 Module: DME (gasoline) or DDE where applicable Key evidence: the commanded cylinder 3 injection event has an open or implausible electrical load Typical causes: a backed-out terminal, oil or water in the injector plug, broken control wire, open injector winding, shared supply loss, or damaged DME output stage Severity: diagnose promptly Note: confirm engine and circuit variant by VIN First save the freeze frame. If the commanded cylinder 3 injection event has an open or implausible electrical load, test cylinder 3 injector power feed, connector and DME low-side driver before disconnecting parts or erasing the evidence. Symptoms • The characteristic pattern is a cylinder-specific dead miss, raw-fuel odor or lean exhaust pulse, shaking under load and catalyst-threatening misfire counts. First save the freeze frame. If the commanded cylinder 3 injection event has an open or implausible electrical load, test cylinder 3 injector power feed, connector and DME low-side driver before disconnecting parts or erasing the evidence. • The freeze frame is most useful when it captures that the commanded cylinder 3 injection event has an open or implausible electrical load. • A graph of the affected channel beside its companion or target value exposes dropouts that a static scan misses. • Related faults should be sorted by time and module so a shared supply or mechanical cause is not mistaken for a second failure. Possible Causes Begin with accessible connections and supporting conditions, prove the component dynamically, and reserve expensive internal work for last. • Low cost: inspect terminal grip, contamination, strain and loom routing at cylinder 3 injector power feed, connector and DME low-side driver. • Low cost: verify the exact fuse, shared feed, ground, hose or oil path shown for the VIN instead of assuming a universal BMW layout. • Medium cost: dynamically test the named sensor, valve or actuator; decisive evidence is that the commanded cylinder 3 injection event has an open or implausible electrical load. • Medium cost: correct the verified system fault, with branches including a backed-out terminal, oil or water in the injector plug, broken control wire, open injector winding, shared supply loss, or damaged DME output stage. • High cost: consider DME repair or internal mechanical work only after circuit loading, signal comparison and the VIN-specific BMW test plan agree. Diagnosis Steps with OBDThink OBDThink is an independent BMW coding and diagnostic mobile app and is not affiliated with BMW AG. Live data and freeze frame depth depend on the vehicle, adapter and module. • 1. Scan all modules with OBDThink; save P0203, the recording DME, status, frequency, companion faults and freeze frame before clearing. • 2. Recreate the stored condition safely and graph the affected signal against its target or redundant channel. Compare cylinder rough-running and misfire counters, then move only a compatible coil or plug before electrically testing the named injector. • 3. Inspect cylinder 3 injector power feed, connector and DME low-side driver; with power isolated where required, load-test supply and ground and check the signal dynamically rather than trusting continuity alone. • 4. Separate electrical from mechanical evidence by moving the harness while logging, then perform the relevant smoke, waveform, pressure, airflow, compression or oil-path test. • 5. After the proven repair, clear faults, repeat the relevant cold start or controlled drive cycle, and rescan every related module. IF the commanded cylinder 3 injection event has an open or implausible electrical load AND the circuit load test fails -> repair the circuit ELSE IF the command is valid but the mechanism does not respond -> test cylinder 3 injector power feed, connector and DME low-side driver ELSE compare companion faults and the BMW VIN-specific test plan THEN clear, reproduce the condition, and rescan The fastest split is command versus response while testing cylinder 3 injector power feed, connector and DME low-side driver: a lost electrical load and a mechanically unresponsive part require different repairs. Repair • Low cost: reseat or repair the proven connector, terminal, wire, hose, ground, fuse path or oil-service error affecting cylinder 3 injector power feed, connector and DME low-side driver. Low cost: inspect terminal grip, contamination, strain and loom routing at cylinder 3 injector power feed, connector and DME low-side driver. • Medium cost: replace the confirmed sensor, valve, solenoid, coil, injector or actuator; perform only the adaptation specified for that VIN. Medium cost: dynamically test the named sensor, valve or actuator; decisive evidence is that the commanded cylinder 3 injection event has an open or implausible electrical load. • Medium cost: repair the demonstrated intake, EVAP, fuel, exhaust, airflow or oil-supply condition instead of masking its measurement. Medium cost: correct the verified system fault, with branches including a backed-out terminal, oil or water in the injector plug, broken control wire, open injector winding, shared supply loss, or damaged DME output stage. • High cost: repair the DME, timing hardware, cylinder head, pump or internal engine only when BMW service-data tests exclude cheaper branches. The fastest split is command versus response while testing cylinder 3 injector power feed, connector and DME low-side driver: a lost electrical load and a mechanically unresponsive part require different repairs. After repair, verify that the commanded cylinder 3 injection event has an open or implausible electrical load no longer occurs and that P0203 stays absent as pending and confirmed through the relevant monitor. Can You Drive with P0203? Do not continue with a flashing warning lamp, raw fuel, severe shaking or catalyst overheating. Treat P0203 as measured evidence. The saved operating condition, target-to-actual comparison and loaded circuit test identify the least costly defensible repair.