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Home >> BMW >> 1994 >> 850CSi >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self Diagnostics >> Component Tests >> Air Mass Sensor >> Check HLM Signal

Check HLM Signal

  1. Load signal TI provides an indication of measured airflow rate in HLM. When idling, value should be 2.0 ms +/- 20 percent. In the case of a break in the voltage supply or in signal line, value is a constant 2.2 ms (substitute value) at idle speed and zero ms under part load and full load.
  2. Load signal is formed dependent upon voltage (less than 5 volts) applied at hot wire of HLM. Load signal is displayed in BMW SERVICE TESTER only when engine is in operation.
  3. Voltage value of hot wire can be measured between pin No. 14 (sensor ground) and pin No. 41 (signal HLM) of DME control unit. This measurement can also be conducted with the ignition ON (nominal value approximately 1.4 volts).
  4. The load signals of the 2 rows of cylinders must scarcely deviate from each other. Check the burn-clear function if the load signal is permanently too low. A load signal which is too low tends to produce a lean mixture, thus reducing engine output.
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