John Deere 1548.03 – ATC: Outlet Air Temperature Sensor Circuit Voltage High

A high voltage condition has been detected on the vent outlet air temperature sensor roof module, which is part of the ClimaTrak automatic temperature control (ATC) system. The sensor's output voltage to the control module has exceeded the predefined threshold, typically greater than 4.8 or 4.93 volts DC. This corresponds to an abnormally high electrical resistance (greater than 60KΩ), causing the system to read an extremely cold temperature outside its operational range (such as -22°F or -30°C). This typically indicates an electrical fault, such as an open circuit on the ground wire, a short to a power source in the signal wire, or a failed sensor.

• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6020 to 6920 series
• 6120L to 6520L series
• 7715
• 7815
• 7720
• 7820
• 7920
• 8120-8520 series
• 8130-8530 series
• 8230T-8430T
• 8RT series (8310RT, 8335RT, 8360RT)
• 9030 series
• 9560 STS
• 9660 STS
• 9760 STS
• 9860 STS
• 9660 CTS

1. 1

   Cycle the power by restarting the engine to verify if the active Service Code reappears, as communication messages can sometimes trigger a false code.

2. 2

   Inspect the wiring harness and connections leading to the sending unit (Component B128) for pinched wires, rubbed insulation, or disconnected plugs.

3. 3

   Use a multimeter to check the B128 circuit for an open circuit or a short to a power supply lead.

4. 4

   Measure the resistance of the sensor itself. If it reads greater than 60K Ohms at normal ambient temperatures, the sensor has failed internally.

1. 1

   Access the HVAC Unit

   Locate the evaporator housing/HVAC unit (typically located in the cab roof or under the seat depending on the specific machine model).

2. 2

   Locate the Sensor

   Find the "Sending Unit for Actual Outlet Air Temperature" (Component ID: B128).

3. 3

   Disconnect and Remove

   Unplug the electrical connector from the B128 sensor. Remove the sensor from the air distribution housing.

4. 4

   Install the New Sensor

   Insert the replacement sensor into the housing and secure it.

5. 5

   Reconnect

   Plug the wiring harness back into the sensor.

6. 6

   Clear Codes

   Turn the key on, access the CommandCenter or diagnostic display, and clear the stored ATC 001548.03 code. Run the ClimaTrak system to ensure the code does not return and the air temperature regulates properly.