This service bulletin addresses a potential issue with the Ambient Air Temperature Sensor Harness in Freightliner trucks manufactured between 1983 and 2013. The bulletin covers a wide range of Freightliner models, including the FLA COE, FLB COE, FLD Conventional, Business Class, FLC 112 Conventional, Century Class Conventional, Argosy COE, Cargo, Columbia, Coronado, Business Class M2, and Cascadia. The bulletin provides detailed information about the potential for chaffing on the Ambient Air Temperature Sensor Harness, which can lead to sensor malfunction or damage. It includes diagnostic steps to identify the issue and recommended repair procedures to address the problem. The service bulletin also includes helpful illustrations and diagrams to clarify the repair process.

The Ambient Air Temperature Sensor Harness Chaffing issue is a common problem affecting a wide range of Freightliner trucks, including popular models such as the FLA, FLB, FLD Conventional, Business Class, FLC 112 Conventional, Century Class Conventional, Argosy COE, Cargo, Columbia, Coronado, Business Class M2, and Cascadia. This issue occurs when the harness, which houses the wires connecting the ambient air temperature sensor to the vehicle's electronic control unit (ECU), experiences excessive wear and tear due to chafing or rubbing against other components. This can happen due to a variety of factors, such as vibration, tight spaces, or improper routing. The chaffing can damage the wiring, leading to a loss of sensor signal, incorrect readings, and potentially even triggering malfunction indicator lamps (MIL) on the dashboard. The ambient air temperature sensor plays a crucial role in optimizing engine performance and fuel efficiency. By providing the ECU with real-time data on the surrounding air temperature, it allows the engine control system to adjust parameters such as fuel injection timing, spark advance, and air-fuel ratios accordingly. This ensures optimal combustion and reduces emissions. When the sensor harness is damaged due to chaffing, the ECU receives inaccurate or incomplete information, leading to potential performance problems. In severe cases, the damage could short circuit or even completely sever the wiring, resulting in a complete loss of sensor data and potential engine misfires or stalling. To ensure safe and efficient operation, it is crucial to address this harness chaffing issue promptly and effectively.