Field Service Mode Check (Except PFI CADILLAC)
WARNING: This page does not describe the selected car, but rather 39 other vehicles, including the 1992 Saturn SL2, 1992 Saturn SL1, 1992 Saturn SL, 1992 Saturn SC, and 1992 Pontiac Sunbird. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Oxygen (O2) sensor may cool off while engine is idling. This causes system to go into "open loop". To restore "closed loop" mode, run engine at part throttle several minutes and accelerate from idle to part throttle several times. For field service mode check on PFI Cadillac vehicles, see appropriate G - TESTS W/ CODES article in this section.
Field service mode check confirms proper fuel system operation 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. Parking brake on FWD models does NOT hold drive wheels.
- Start engine. With engine running, ground test terminal "B" of the ALDL diagnostic connector. See Fig 1. In "closed loop" mode, SERVICE ENGINE SOON light will flash once a second.
- In "open loop", light will flash 2.5 times a second. If light is off most of the time, a lean exhaust is indicated. If light is on most of the time, a rich exhaust is indicated.