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The Coolant Level Sensor (CLS) is a two-piece sensor for DDEC II, and a single sensor for DDEC III/IV. See Figure 34754 . The sensor probe (supplied by the vehicle, vessel or equipment manufacturer) is mounted in the top tank or overfill tank. For DDEC II the sensor module is mounted on the vehicle. The module sends an electrical signal to the ECM to indicate coolant level. Low coolant will activate the stop engine function or warning function. ‪

Coolant Level Sensors

Replacement of Coolant Level Sensor

Both the CLS sensor probe and module are non-serviceable and should be replaced as necessary. ‪

Removal of Coolant Level Sensor

Remove the CLS as follows: ‪

  1. Open the drain cock at the bottom of the radiator and drain the coolant into an appropriate container. Remove only as much coolant as is necessary to clear the CLS probe.
  2. Remove ground wire screw and ground wire from side of probe.
  3. Loosen and remove nut from sensor lead of probe.
  4. Remove sensor lead, or unplug the two-pin connector.
  5. Use the appropriate wrench on the hex portion of the sensor and unscrew it from the radiator.

Installation of Coolant Level Sensor Probe

Install the CLS Probe as follows: ‪

  1. Install CLS probe into the radiator or heat exchanger as follows:

    Note: New sensors are pre-coated with a thread sealer. If sensor is new, no additional sealant is required. If sensor is reused, apply Loctite 567 pipe sealant with Teflon or equivalent.

    Loctite is a registered trademark of the Loctite Corporation. ‪

    Teflon is a registered trademark of the E. I. DuPont de Nemours and Company, Inc. ‪

    1. Install and torque vehicle or industrial engine CLS to 810 lbft (1114 Nm).
    2. Install and torque marine engine CLS to 46 lbft (58 Nm).
  2. Connect the two-pin connector.
  3. Fill the cooling system. Refer to section .
  4. Turn the ignition to the ON position. Observe or read any diagnostic code(s). If any code other than code 25 appears, refer to the DDEC Troubleshooting Guide: 6SE477 (DDEC I), 6SE489 (DDEC II), or 6SE497 (DDEC III/IV).


    To avoid injury before starting and running the engine, ensure the vehicle is parked on a level surface, parking brake is set, and the wheels are blocked.


    Diesel engine exhaust and some of its constituents are known to the State of California to cause cancer, birth defects, and other reproductive harm.

    • Always start and operate an engine in a well ventilated area.
    • If operating an engine in an enclosed area, vent the exhaust to the outside.
    • Do not modify or tamper with the exhaust system or emission control system.
  5. Start the engine and check for leaks.
  6. Shut down engine upon completion of test. Perform necessary repairs.

Removal of Coolant Level Sensor Module

Remove the CLS module as follows: ‪

  1. Disengage the locking tang on the CLS module connector. Grasp the connector bodies and gently pull them apart.
  2. Remove module from vehicle.

Installation of Coolant Level Sensor Module

Install the CLS Module as follows: ‪


Use care during the installation of the CLS module or damage may occur. ‪

  1. Insert the CLS module to the vehicle.
  2. Grasp both connector bodies. Gently push them together and engage locking tang on the CLS module connector.