Field Service Mode Check

This test confirms proper operation of fuel system and verifies "Closed Loop" operation. Clear codes and perform this test after any repair is completed.
When performing this check, always engage parking brake and block drive wheels.
On some engines, the oxygen sensor will cool off after only a short period of time while engine is idling. This will cause engine to go into open loop. To restore closed loop mode, run engine at part throttle for several minutes, accelerating from idle to part throttle several times.