BMW 002ACC: DME: DME master relay, shift delay

002ACC means DME: DME master relay, shift delay. The DME stores it when the electrical response of its master power relay does not follow the requested switching moment. Depending on the vehicle architecture, the controlled path may use a separate E-box relay or an Integrated Supply Module, so VIN-specific identification comes before testing. What Does 002ACC Mean? 002ACC is a timing fault in the DME master-relay power path, not proof that the control unit itself has failed. The DME compares its relay command with the arrival or removal of operating voltage and recognizes a response that occurs later than the calibrated switching window. In practice, the fault can concern relay contacts that move sluggishly, excessive resistance between the battery feed and DME supply, or a control signal that changes late. BMW lists MSD80, MSD80N43, MSD85, MSD85Y, and MSS70 variants for this definition, making module and wiring identification essential. Code: 002ACC Definition: DME: DME master relay, shift delay Module: DME, including supported MSD80/MSD85/MSS70 variants Key data: relay command compared with DME supply-voltage transition Typical cause: slow relay contacts or resistance in the controlled feed Severity: medium; high if starting becomes intermittent Note: verify the VIN-specific relay architecture before replacement First preserve the freeze frame, then observe whether DME supply voltage changes promptly when the relay command changes. What Symptoms Does 002ACC Cause? 002ACC can appear as a delayed start, an occasional crank without combustion, or a fault stored after shutdown with no obvious driving complaint. The distinguishing observation is timing: ignition status changes first, while DME communication or supply-powered engine electronics wake up or power down noticeably later than expected. • The starter turns normally, but injector and ignition operation begins late or remains absent during one attempt. • DME communication appears only after cycling ignition, while other control units respond immediately to the scan. • The engine starts on a second attempt after the first attempt records a delayed relay transition. • Supply-powered actuators remain active briefly after key-off, matching a relay that releases later than commanded. • The fault returns during low-voltage starts but disappears when a stabilized battery supply supports the vehicle. • A recorded DME reset or multiple supply-related faults accompany the same ignition-on event as 002ACC. Why Does 002ACC Occur? The code arises when the master-relay circuit cannot change the DME supply state at the commanded time. Begin with battery condition and connection losses, because low control voltage can slow relay pull-in. Continue through the relay or Integrated Supply Module before considering the DME driver that commands the circuit. • A weak battery lets voltage sag during cranking, delaying relay pull-in and the DME supply transition. • Loose battery distribution connections add resistance before current reaches the E-box power-distribution path. • Moisture or heat damage at the relay socket slows current delivery through discolored connector pins. • Worn relay contacts close or release inconsistently after repeated thermal cycling inside the electronics compartment. • An Integrated Supply Module develops an internal switching fault on vehicles that package the relay there. • The DME relay-control output stage changes late despite correct power, ground, wiring, and relay operation. How Is 002ACC Diagnosed with OBDThink? Save the stored event before clearing anything, and compare ignition status, relay command, DME voltage, and reset history during one start and one controlled shutdown. OBDThink is an independent BMW coding and diagnostics app and is not affiliated with BMW AG. Use the VIN-specific BMW wiring plan to locate the actual controlled feed. • 1. Record 002ACC status, occurrence count, battery voltage, engine speed, and ignition state from the stored event. • 2. Scan every control unit for undervoltage or communication faults recorded at the same operating moment. • 3. Stabilize the battery, repeat startup, and note whether the relay delay disappears with supported voltage. • 4. Identify whether this VIN uses a separate relay or an Integrated Supply Module in the E-box. • 5. Plot the relay command beside DME supply voltage through ignition-on and observe which transition lags. • 6. Measure voltage loss across the battery feed and relay contacts while the circuit is carrying load. • 7. Inspect the E-box for moisture, overheated plastic, relaxed connector pins, or corrosion around power distribution. • 8. If command timing is late with a proven external circuit, test the DME output stage professionally. IF battery voltage collapses during cranking AND relay response becomes normal with stabilized support, THEN correct the battery or connection loss first. ELSE IF the relay command changes on time BUT DME supply voltage changes late, THEN test the relay contacts, socket, and controlled feed under load. ELSE IF command timing itself remains late with verified power and ground, THEN investigate the DME control stage. The decisive split is command versus response: a timely command with late voltage points outside the DME logic. How Is 002ACC Repaired? Repair the proven delay source rather than replacing the DME from the fault text alone. Restore battery and connection integrity first, then address damaged relay wiring or the correct relay assembly. DME repair or replacement belongs last, after measurements show that its command output remains delayed with a healthy external circuit. • Appropriate cost: charge, test, or replace a weak battery and register it when the vehicle requires registration. • Appropriate cost: clean and secure battery distribution, ground, and E-box connections that fail loaded testing. • Moderate cost: repair heat-damaged relay-socket wiring and replace terminals that no longer maintain contact pressure. • Moderate cost: replace the confirmed separate master relay with the exact part specified for the VIN. • Higher cost: replace a diagnosed Integrated Supply Module when its internal relay response remains delayed. • Higher cost: repair or program the DME only after its output stage fails a controlled circuit test. After repair, 002ACC should no longer occur through repeated cold starts, warm restarts, and controlled key-off cycles. Can You Drive with 002ACC? A car that starts normally and stores 002ACC only as history can usually be moved for diagnosis, but reliability is uncertain because the DME supply may fail on the next start. Avoid remote trips until relay timing and battery voltage have been checked under the conditions captured in the freeze frame. Stop driving if the engine stalls, the DME repeatedly resets, starting becomes intermittent, or electrical burning odor comes from the E-box. Continued relay arcing can heat connectors and a loss of DME supply may stop the engine without a predictable warning. Arrange recovery when those symptoms appear. Do not continue if stalling, hot-plastic odor, smoke, or repeated total loss of DME communication occurs. Which Questions Are Frequently Asked? Owners often want to know whether 002ACC identifies one replaceable relay and whether clearing it proves success. The answers depend on the fitted supply architecture and on a measured command-to-voltage delay. These checks prevent an unnecessary control-unit replacement and preserve evidence of an intermittent fault. • Does 002ACC always mean a bad DME? No. Slow relay contacts, low battery voltage, or resistance in the supply path are more direct possibilities and must be excluded first. • Can clearing 002ACC fix the starting problem? No. Clearing removes evidence, but a delayed electrical transition returns when the same voltage and temperature conditions recur. • Is the master relay always a separate part? No. Its location and packaging vary, so identify the VIN-specific E-box or Integrated Supply Module arrangement before ordering parts. • What confirms the repair? The relay command and DME supply-voltage transition align during repeated starts and shutdowns, while 002ACC no longer returns. Use the stored timing evidence to decide whether the delay begins before the relay command or after it. That single comparison directs the next measurement toward battery support, relay contacts, the controlled feed, or the DME output stage without guessing at expensive modules.