Who is correct regarding the slow warm-up of a late-model diesel engine?

In a late-model diesel engine, technicians generally monitor various parameters, including temperature, to ensure optimal operation. When a diesel engine warms up slowly, it can trigger fault codes that indicate the engine is not reaching the required operating temperature in a timely manner. Many engines are equipped with advanced diagnostics that monitor the warm-up process, and if the engine takes too long to reach the proper temperature, the system may interpret this as a malfunction.

While there are instances when a slow warm-up might be within acceptable limits, such as extreme environmental conditions or certain design aspects of the engine, the primary concern is that it doesn't reach its operating temperature efficiently. Therefore, it's crucial to recognize that a slow warm-up can lead to fault codes, signaling potential issues that need addressing for optimal performance and engine longevity.