John Deere 524202.03 – ATC (Automatic Temperature Control): High Voltage On Ambient Air Temp Cab Roof Above Right Side Front Corner / B126 Sensor for Ambient Air Temperature (at Rear), Voltage Too High.

The control unit has detected a voltage exceeding 5 volts at the signal input for the rear ambient air temperature sensor (designated as sensor B126, lead 2006). A high voltage reading typically indicates that the sensor circuit is either shorted to a power supply lead or has an open circuit. When this fault is active, the system may restrict automatic temperature control functions, and ambient temperature readings may default to the front sensor (B125) if applicable.

• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6230
• 6330
• 6430
• 8130
• 8230
• 8330
• 8430
• 8530
• 8230T
• 8330T
• 8430T
• 8245R through 8400R
• 9470RT
• 9520RT
• 9570RT
• CH570
• CH670
• 4730
• 4830
• 4940

1. 1

   Visually inspect the B126 ambient air temperature sensor, connector, and wiring harness in the cab roof for physical damage, corrosion, or loose pins.

2. 2

   Measure the 5V reference supply voltage at the sensor connector using a multimeter (should read between 4.8 and 5.2 volts).

3. 3

   Test the signal wire (lead 2006) for a short to a 12V power source.

4. 4

   Test the circuit for continuity to ensure there is no open circuit between the sensor connector and the ATC module.

5. 5

   If the wiring harness tests good (no opens, no shorts to power, and proper ground/reference voltage is present), verify if the sensor itself has failed internally.

1. 1

   Turn off the machine and disconnect the battery ground to prevent electrical spikes.

2. 2

   Access the cab roof panel where the B126 ambient air temperature sensor is housed.

3. 3

   Disconnect the wiring harness from the faulty ambient air temperature sensor.

4. 4

   Remove the mounting hardware/clips securing the sensor and remove the old unit.

5. 5

   Install the new ambient air temperature sensor and secure it in place.

6. 6

   Reconnect the wiring harness, ensuring the connector clicks and locks securely to prevent moisture intrusion.

7. 7

   Reassemble the cab roof paneling.

8. 8

   Reconnect the battery, turn the key to the ON position, and use a diagnostic tool (or the tractor's onboard CommandCenter display) to clear the ATC 524202.03 fault code.

9. 9

   Test the ClimaTrak/ATC system to verify that the A/C functions normally and the code does not return.