BMW 318/325/M3/525/535/M5 1989-1993 Repair Information

Diagnosis and Testing



BMW offers the following cautions that should be observed to protect the DME system and components:

Always disconnect the battery, the DME control unit and the ignition coils when using an electric welder on the vehicle or when charging the battery or when the vehicle is placed in a paint drying oven.
Remove the main DME relay to disable both the fuel and ignition systems when checking the compression. Never crank the engine after removing the distributor cap or disconnecting the high tension wire on the ignition coil.
Never apply more than standard battery voltage to the electrical system. This includes 24 volt jump starters or battery chargers.
Never disconnect the battery or wires on the alternator, starter or spark plugs when the engine is running.
Never connect a test lamp on terminal 1 of the ignition coil.
Never connect terminal 1 of the ignition coil with ground or B+. This means if installing a burglar alarm, terminal 1 should not be used for starter interlocking.
Whenever performing work on the EML throttle by wire system, a check of the external safety path must be made. This is to check the proper operation of the EML safeguards.
When working with the EML throttle by wire systems do not place hands or fingers in or near the throttle plates. The throttle motors can close the throttle plates with considerable force.



The external safety path must be checked anytime a component of the EML throttle by wire system is removed or adjusted.

  1. Read all fault codes from the EML memory before checking the external safety path. This will require the BMW Diagnostic tester or equivalent.
  3. Turn the ignition switch to OFF . Unplug the EML connector. The EML connector is grouped with the DME engine connector and the diagnostic connector on the left side of engine compartment near the fuse box.
  5. Install the EML testing adapter 12 7 010 or equivalent to the EML connector inline. Make sure all connections are tight.
  7. Turn the knob on the tester to the left position and start the engine. Adjust the engine speed to 2500 rpm with the tester knob.
  9. Depress the brake pedal. The engine speed should drop immediately due to the overrun shutoff provision.
  11. If the engine speed does not drop immediately, check the EML system for faults. If the speed does drop immediately, the EML external safety path is functioning.
  13. Shut off the engine and remove the tester. Reconnect the EML connector and erase any fault codes from the EML control unit.