Saturn Scan Tool (PDT) Fuel Economy Special Test

After the fuel economy test has been downloaded onto the Saturn Portable Diagnostic (Scan) Tool (PDT) from the Service Stall System (SSS), the test can be selected from the PDT main menu. This test provides a way of checking instant and average fuel economy while operating the vehicle under normal operating conditions. This test uses fuel injector(s) pulse widths and vehicle speed sensor reading to estimate fuel usage. Before using this test to evaluate fuel economy on a vehicle, check for proper fuel pressure and vehicle speed sensor operation.

NOTE:Erratic speed readings, fuel pressures out of range or adverse driving habits may cause false MPG readings (ex. high pressure = lower than displayed MPG, repeated long decel conditions = higher than normal MPG's displayed).

After entering the fuel economy test you will be prompted to select Instant or Average Fuel Used, scroll to your desired choice using arrow keys and hit Enter to select. Scroll to English or Metric and hit enter to select display units. When performing a fuel economy test on a vehicle with diagnostic trouble codes or information flags stored in memory, the stored diagnostic trouble codes and/or information flags will be displayed (correcting the cause of a DTC can often correct a poor fuel economy complaint).

Instant Fuel Used:
When instant fuel used is selected, Miles/Gal are calculated and displayed every half second. Instant fuel used will closely follow driving conditions. This selection should be used when checking driving habits and adverse driving conditions.

Hit enter to stop calculating instant fuel used.

Average Fuel Used:
When average fuel used is selected, Miles/Gal are calculated over time and distance traveled since starting average test. The Miles/Gal will be displayed and updated according to fuel believed delivered by injector(s). The update rate will appear to slow down as more time and distance have past. Average fuel is calculated over time since start of test or last reset.

Hit enter to reset average fuel used.

Follow the directions on bottom line of display to select, continue, reset, stop or abort from the test. The FUNCTION key provides a means of stepping back in test.