In flight, what additional fault light will illuminate for a green or yellow system reservoir problem besides the PTU FAULT light?

In the context of the A320's hydraulic system, when there is a reservoir issue with either the green or yellow hydraulic system, the corresponding fault light that illuminates provides critical diagnostic information to the flight crew. The illuminated ENG 1 or 2 PUMP FAULT light indicates a problem with the engine-driven hydraulic pumps, which are vital for hydraulic system operation.

When the hydraulic fluid levels in the reservoirs are low or if there is any malfunction in the hydraulic system that prevents adequate fluid flow, it directly affects the performance of the engine-driven pumps. The ENG PUMP FAULT light serves as a warning that the hydraulic system may not be operating efficiently, thus highlighting a potential risk to normal aircraft operations.

This warning is essential for maintaining safety and ensuring the crew can take necessary actions, such as managing hydraulic system loads or preparing for potential system failures. The fault light acts as a prompt for the crew to investigate further and take appropriate measures to mitigate the risk associated with low hydraulic fluid levels.