Fault Condition
WARNING: This page is about a different car, the 1994 Volvo 960. However, it is still accessible from the selected car via links, so may be relevant.
The ECM receives information from the HO2S on air/fuel mixture. If air/fuel mixture deviates from l=1, the short-term fuel trim compensates for it by adjusting the injection period. If the short-term fuel trim remains lean for more than 3 minutes and engine temperature exceeds 75°C (167°F), DTC 5-1-2 is set.