Circuit Description

When power enrichment is requested from PCM, the PCM monitors O2S reading to ensure power enrichment has been achieved. If during power enrichment, rich exhaust is not detected by the PCM, DTC 1171 will set.

Conditions required to set DTC are:

• No related DTCs are set.
• Engine is operating in closed loop power enrichment mode.
• ECT is above 140°F (60°C).
• O2S voltage remains below .4 volts for 5 seconds, while in power enrichment mode.