Circuit Description

PCM monitors oxygen sensor signal voltage and adjusts fuel delivery based on signal voltage. A change made to fuel delivery is indicated by the long and short term fuel trim values. Ideal fuel trim value is about 128 (zero percent).

If HO2S signals are indicating a lean condition, the PCM will add fuel, resulting in fuel trim values greater than zero percent. If a rich condition is detected, fuel trim values will be less than zero percent, indicating that PCM is reducing amount of fuel delivered.

Conditions for setting this DTC are as follows:

• No active misfire, fuel injector circuit, TP sensor, EVAP, IAT sensor, MAP sensor, fuel trim, EGR, ECT sensor, MAF sensor or CKP sensor DTCs set.
• ECT is 68-230°F (20-110°C).
• IAT 0-149°F (-18 to 65°C).
• TP sensor angle is less than 90 percent.
• Vehicle speed is less than 82 MPH.
• Engine speed is 600-4000 RPM.
• Long Term (LT) fuel trim is about +16 percent.
• Short Term (ST) fuel trim is about +20 percent.
• BARO is greater than 70 kPa.