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Home >> BMW >> 1989 >> 635CSi Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Basic Testing >> Fuel System >> Engine Speed/Reference Sensor & Circuit >> Sensor & Circuit Checking Procedure
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Sensor & Circuit Checking Procedure

  1. With ignition off, remove connector from the sensor. Sensor is located on front of engine near crankshaft pulley.
  2. Turn ignition on and check voltage at Black wire of connector. Voltage should be approximately 5 volts. If voltage is not within specification, check wiring circuit between MCU pin No. 47 (Black wire) and sensor.
  3. Check voltage between both terminals of the sensor connector. Voltage should be approximately 5 volts. If voltage is not within specification, check wiring circuit between MCU pin No. 48 (Yellow wire) and the sensor.
  4. If all voltages are correct, reinstall sensor connector. Sensor can be checked with ohmmeter or oscilloscope. Ensure ignition is off. Unplug sensor.
  5. Resistance across 2 connector terminals (sensor side) should be as specified. See ENGINE SPEED/REFERENCE POINT SENSOR table. Connect ohmmeter between each sensor terminal and engine block. Ohmmeter should not show continuity. Replace sensor if continuity exists.
  6. To check sensor with oscilloscope, unplug sensor. Connect oscilloscope leads across the 2 sensor terminals. Remove fuel pump relay to prevent engine from starting. Crank engine. Oscilloscope should show a sign wave as engine is cranked.
ENGINE SPEED/REFERENCE POINT SENSOR

Application Ohms
All Models 490-550