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Coolant Temperature Sensor

  1. A new 4-pole CTS is used for EZL ignition systems. It combines two sensors into one housing. Neither sensor is connected to housing for grounding purposes. One sensor is for EZL ignition system (terminals No. 1 and 3) and other sensor is for CIS-E fuel injection system (terminals No. 2 and 4). Both CTS sensors are internally identical so that harness connector can be attached in any position to CTS.
  2. Unplug CTS harness connector. Using ohmmeter, check resistance value across diagonally opposite terminals of the CTS. See Fig 1. Refer to coolant temperature resistance chart for resistance specification at engine coolant temperature. See Fig 2. If resistance values are not to specification, replace coolant temperature sensor.
NOTE: Always test CTS sensors at two different coolant temperatures.
Fig 1: Testing Coolant Temperature Sensor Resistance
G91C17469Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
Fig 2: Coolant Temperature Sensor Resistance Chart
G48217Courtesy of MERCEDES-BENZ OF NORTH AMERICA.