Freightliner new ultrasonic fuel level sensor information

Applicable Vehicles

Cascadia, New Cascadia, M2, Coronado, Western Star and possibly others depending on customer order preferences.

Symptoms

Fuel gauge reading inaccurate.

Fuel gauge reading empty all the time.

Fault codes for fuel level sensor.

Issue

The SSI Ultrasonic Fuel Level Sensor sends high frequency pulses then measures the echo in order to determine the fuel level in the tank. To test the resistance output of this ultrasonic sensor the sensor needs to be properly connected to power and ground. 

Solution

NOTE: When using jumper wires make sure the connections to the terminals are snug and the terminals are protected from coming into contact with each other.

1. With ignition in “off” position:
Disconnect the fuel level sending unit and insert test wires between Pins A and Pins C of the vehicle harness and sender.
Pin A to Pin A
Pin C to Pin C
Do not connect Pin B to the vehicle harness.

2. With ignition in “on” position:
Measure voltage between Pin A (black wire) and Pin B (red wire).
Voltage should be 12- 14 volts.

3. With ignition in “on” position:
Measure resistance between Pin A (black wire) and Pin B (yellow wire).
Resistance should be close to:
Full Tank 30 Ohms
3/4 Tank 76 Ohms
1/2 Tank 103 Ohms
1/4 Tank 152 Ohms
Empty 236 Ohms

If resistance values are out then check for proper installation of the fuel level sender per page 2 of this document.

Visual Inspection for Proper Installation of Ultrasonic Fuel level Sender

Confirm that fuel tank is oriented with fuel level sender level on the highest point on the top of the tank (fuel level sender positioned within +/-10° of highest
point on the tank)
• Confirm that the proper gasket is present between the aluminum tank flange and the focus tube assembly, and the proper gasket is present between the
focus tube assembly and the ultrasonic fuel level sender.
• Confirm that 5 mounting screws are tightened uniformly (15 in lbs max) to ensure that ultrasonic level sender is parallel to the fuel surface.
• Inspect cable harness electrical connectors for corrosion, dirt, and water ingress.
• If all of the above items are as specified and the fuel level sender is not providing the correct signal, please record any diagnostic fault codes, and
results of the above diagnostic procedure.