Vehicle: 2021 Dodge Ram 1500, 4WD, V6-3.6L eTorque, MHEV Automatic

Mileage: 107,234 Miles

Problem: The Acadia was in the shop because the A/C suddenly stopped working.

Case Details: The technician connected a scan tool and found the following three diagnostic trouble codes (DTCs).

• B018A-Windshield Temperature Sensor Circuit (ATC)
• B048C-Humidity Sensor Humidity Circuit (ATC)
• B048F-Humidity Sensor Temperature Circuit (ATC)

He checked the humidity sensor with the scan tool, which read -38 degrees and 100% humidity, so it appeared the sensor was bad. Just to be thorough, he also tested the A/C system, which showed good high and low static pressures, and he could command the A/C fan to operate with the scanner.

Based just on the DTCs, the problem appeared to be the humidity sensor, which should be located on the windshield. He removed the trim piece behind the rearview mirror, but there was no sensor and no sign that there had ever been a sensor. The customer said that they've had the vehicle for a while and have never replaced the windshield. It was time to call an ALLDATA Tech-Assist consultant.

The consultant said that it was possible the three DTCs were the only way the module could communicate the problem, even though it wasn’t the exact problem. It was time to inspect all the A/C system electrical components.

When the technician checked the compressor clutch, he noticed that coolant from the water pump had been leaking directly onto the compressor clutch.

Confirmed Repair: The technician replaced the A/C compressor clutch and the water pump, then cleared the DTCs. The A/C system worked perfectly, and the DTCs did not return. Fixed!