Q21-1029-1-121 | Genuine Paccar® Cab Control Module

• Manages climate control / HVAC, including fan speed and temperature settings

• Controls seat adjustments, if equipped

2. Operate Cabin Electronics

• Powers and regulates interior lights (dome lights, map lights)

• Controls power windows, door locks, and mirrors

• Manages wipers and windshield washers

3. Coordinate Communication Between Systems

• Acts as a hub, communicating with other vehicle modules via CAN bus or other networks

• Ensures commands from switches or touch panels are sent to the right components

4. Enhance Safety and Diagnostics

• Sends signals to dashboard warning lights if a cabin system fails

• Stores trouble codes for easier troubleshooting by mechanics

1. Interior Electrical Malfunctions

• Dome lights, map lights, or dashboard lights stop working or work intermittently

• Power windows, door locks, or mirrors malfunction

2. HVAC or Climate Control Issues

• Blower fan, temperature, or air distribution doesn’t respond properly

• Cabin temperature cannot be adjusted correctly

3. Warning Lights or Error Codes

• Dashboard warning lights related to cabin systems turn on

• Stored Diagnostic Trouble Codes (DTCs) in the CCM

4. Erratic or Unpredictable Behavior

• Electrical accessories turn on/off randomly

• Functions respond slowly or not at all

5. Failure of Multiple Systems at Once

• Several cabin features fail simultaneously, which often indicates a central control issue rather than individual component failure

6. Communication Issues

• The CCM may fail to communicate with other modules, leading to errors in CAN bus networks or problems with integrated systems