P0504 identifies Brake Switch A B Correlation. Diagnosis compares brake switch A, brake switch B, pedal status, cruise release, brake-lamp state, and supply voltage so the failed electrical or mechanical path is isolated before repair.
P0421 identifies Warm Up Catalyst Efficiency Below Threshold Bank 1. Diagnosis compares upstream and downstream lambda traces, catalyst temperature, cold-start enrichment, misfire counters, and exhaust sealing so the failed electrical or mechanical path is isolated before repair.
P0345 identifies Camshaft Position Sensor A Circuit Bank 2. Diagnosis compares Bank 2 intake-cam angle, crank synchronization, sensor supply, signal waveform, and VANOS target so the failed electrical or mechanical path is isolated before repair.
P0444 identifies Evaporative Emission Purge Control Valve Circuit Open. Diagnosis compares purge command, valve current, fuel trims, tank pressure, and control-wire voltage so electrical, hydraulic, and mechanical causes are separated before repair.
P0405 identifies EGR Sensor A Circuit Low. Diagnosis compares EGR command, position feedback, MAF response, MAP response, and sensor reference voltage so electrical, hydraulic, and mechanical causes are separated before repair.
P0320 identifies Ignition or Distributor Engine Speed Input Circuit Malfunction. Diagnosis compares crankshaft speed, synchronization status, cam signals, sensor supply, and waveform dropout so electrical, hydraulic, and mechanical causes are separated before repair.
P0200 identifies Injector Circuit Open or Malfunction. Diagnosis compares individual injector command, current ramp, cylinder smooth-running values, and supply voltage so electrical, hydraulic, and mechanical causes are separated before repair.
P0139 identifies O2 Sensor Slow Response Bank 1 Sensor 2. Diagnosis compares Bank 1 Sensor 2 voltage or lambda response, upstream switching, fuel trims, and catalyst temperature so electrical, hydraulic, and mechanical causes are separated before repair.
P0019 identifies Crankshaft Position and Camshaft Position Correlation Bank 2 Sensor B. Diagnosis compares crank synchronization, exhaust-cam target, actual exhaust-cam angle, and VANOS response so electrical, hydraulic, and mechanical causes are separated before repair.
P0004 identifies Fuel Volume Regulator Control Circuit High. Diagnosis compares regulator command, control-line voltage, valve current, and requested versus actual rail pressure so electrical, hydraulic, and mechanical causes are separated before repair.
P2402: EVAP Leak Detection Pump Control Circuit High. The DME detects a high electrical state in the EVAP leak-detection pump control circuit. On BMW vehicles this pump is commonly part of the DMTL assembly, but circuit direction must be proven before replacing it.
P2195: O2 Sensor Signal Biased or Stuck Lean, Bank 1 Sensor 1. The DME finds Bank 1 Sensor 1 biased or stuck on the lean side. A true lean mixture, exhaust air leak, slow lambda element and signal-circuit fault produce different fuel-trim and response patterns.