1985 Mercedes Benz 190D AutomaticFACTORY OEM SERVICE PROCEDURE

Engine Rpm Sensor

On automatic transmission, the engine RPM sensor is installed on a flange toward the transmission. The RPM sensor consists of a magnetic core and coil. When engine speed is between 1150-3000 RPM, the sensor applies AC-voltage to the air conditioning control unit. The transformed signal is then transmitted to control unit.

On manual transmission, the RPM sensor is located on the back of the tachometer head. The vehicle speed is sensed by the RPM sensor on the tachometer. At speeds above 48 MPH a switching unit will switch off the EGR system.

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:

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