1993 BMW 740iFACTORY OEM SERVICE PROCEDURE

Test 7 - Control Unit Simulation (Rear Wheels)

NOTE: Connect ABS adapter between "T" plug and control unit.
  1. Ensure battery is fully charged. Connect "T" plug with adapter "A" to ABS wiring harness connector. Connect "T" plug with adapter "B" to ECU. Connect lead from adapters "A" and "B" to cigarette lighter. Switch to position No. 3 on adapters "A" and "B".
  2. Check left and right rear solenoid pressure build-up, drop and retention individually. Pressure drop should be less than 4.5-5.7 percent. Start engine. Pressure retention should not deviate more than 1.9-2.3 percent.
  3. If solenoid performance is not as specified, replace control unit and repeat step 1). If control valves do not switch or pressure pump does not run in TESTS 8, 9 and 10, replace hydraulic unit.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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