Code P043, Front Oxygen Sensor Rich Signal: Action

WARNING: This page is about a different car, the 1995 Cadillac Eldorado. 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. Transaxle shift adapts are maintained at current levels.

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 at 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 one volt, PCM and circuit No. 412 are okay.

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

Courtesy of GENERAL MOTORS CORP.

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

Courtesy of GENERAL MOTORS CORP.