BMW Bosch ME9.2 DME/ECU

BMW Bosch ME9.2 DME/ECU Post-Repair Troubleshooting Guide

Important: Use this guide if you reinstalled your repaired BMW Bosch ME9.2 DME/ECU and the problem is still happening.
Important: Please do not open/disassemble the DME/ECU. Opening it can damage the unit and may void warranty coverage.

Common concerns this guide helps with:

• Check Engine Light still on
• No communication with DME/ECU
• Rough idle / misfires / ignition coil-related symptoms
• Diagnostic light still on after reinstall
• Intermittent drivability issues

Step 1: Verify the correct module and a clean install

• Confirm you reinstalled the same DME/ECU that was repaired (matching labels/part number)
• Make sure the DME connectors are fully seated and locked
• Inspect connector pins for bent/pushed pins, moisture, or corrosion
• Confirm the DME box (E-box) cover and seals are installed correctly to prevent water intrusion

Step 2: Battery voltage and power stability

• Fully charge the battery before any diagnosis (low voltage causes false DME faults)
• Verify battery terminals are clean and tight
• If the battery was recently replaced/jumped, re-check the connections and IBS area (if equipped)

Step 3: Check fuses and relays that feed the DME

• Check all engine management fuses (DME/ECM/EFI/IGN) in the E-box and cabin fuse panel
• Verify the main DME relay operation (swap with a known-good relay if applicable)
• If a fuse blows again, stop and locate the short before continuing

Step 4: Confirm scan tool communication correctly

• Try scanning with a second scan tool if available (tool limitations can look like “no comm”)
• Verify the vehicle OBD port has power
• If you can’t communicate with multiple modules (not just the DME), suspect vehicle power/CAN issues first

Step 5: If you have “No Communication” only with the DME

• Re-check DME connector seating and locking
• Inspect the wiring at the DME box for rodent damage, rubbed-through wiring, or water entry
• Verify power and ground circuits to the DME are present (a missing power/ground will mimic a bad DME)

Step 6: If the Check Engine Light or codes came back immediately

• Pull codes and record them before clearing
• Clear codes, cycle key, and re-check which codes return instantly
• Prioritize these categories first:
  • Crankshaft/camshaft sensor codes (can cause no-start, misfires, rough idle)
  • Power supply / relay control codes
  • Throttle actuator / throttle adaptation codes
  • CAN communication codes

Step 7: Rough idle / misfires / ignition coil complaints

• Misfires on these BMWs are often vehicle-side:
  • Weak ignition coil(s)
  • Worn spark plugs / incorrect plug type or gap
  • Vacuum leaks (cracked intake boots, PCV/CCV issues)
  • MAF contamination or air leaks after the MAF
• If you have a specific cylinder misfire code, swap coil and plug to see if the misfire follows the part

Step 8: “Diagnostic light on” with drivability changes

• If the issue began after recent work (coils/plugs, intake, battery, alternator, wiring), re-check what was touched
• Inspect intake boots and vacuum lines for cracks/disconnects
• Confirm the throttle body connector is fully seated

Step 9: Water intrusion warning (very important on E-box DMEs)

• If you see moisture/corrosion in the DME box area, address it immediately
• Water intrusion can cause repeat issues even after a successful repair
• Make sure drains, covers, and seals are correct and intact

What to send us if the issue continues

• VIN
• DME part number from the label
• Exact symptom (no comm, rough idle, misfire, CEL)
• Full code list (photos/screenshots preferred)
• Battery voltage (key off + while cranking)
• Photos of the DME connectors/pins and the DME box area if water/corrosion is suspected