Gilly, does this star bulletin apply to what you said.

SUBJECT: Model 163.154/157/172/174/175, up to VIN A488107 Inaccurate Fuel Gauge Before Refueling Vehicle

If you receive customer reports in the above model vehicles of the fuel gauge dropping to minimum too quickly and the customer can only add a small amount of fuel after the “fuel reserve indicator” in the instrument cluster illuminates, this may be due to a software error in the instrument cluster. To resolve, follow the steps below.
1. Install new instrument cluster per WIS document AR54.30-P-6015GH.
2. Carry out “Pointer Actuations” by using WIN/HHT (Star Diagnosis). Instrument Control Module -> 4. Activations -> 2. Analog Instruments-> Click “on”