Conditions for Setting the DTC

WARNING: This page is about a different car, the 2003 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

The primary fuel tank (left) is not full.
More than 241 km (150 mi) have been accumulated.
The PCM does not detect that the fuel level in the left fuel tank has not changed by at least 4.0 liters (1.1 gallons).
OR
The primary fuel tank (left) is full.
The secondary fuel tank (right) is near empty.
The fuel level in both fuel tanks does not change after traveling more than 241 km (150 mi). Observe, if the secondary fuel tank is empty, the primary fuel level should decrease after 241 km (150 mi).