Code P043, Front Oxygen Sensor Signal Rich: Action

WARNING: This page is about a different car, the 1995 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.

PCM turns on MIL. PCM turns on canister purge solenoid if Code P045 is also set.

NOTE: Test numbers refer to numbers on diagnostic chart.

If Code P017 is present, diagnose this code first since an oxygen sensor not ready can cause other emission related problems.
If oxygen sensor is operating correctly, voltage should fluctuate less than 0.6 volt. A rich sensor condition will cause voltage to remain at greater than 0.6 volt.
If voltage measured is less than 0.95 volt, PCM and circuit No. 412 are okay.

Fig 1: Code P043 Schematic, Front O2 Sensor Signal Rich

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code P043 Diagnostic Flow Chart, Front O2 Sensor Signal Rich

Courtesy of GENERAL MOTORS CORP.