Circuit Description
WARNING: This page is about a different car, the 2000 Toyota Celica. However, it is still accessible from the selected car via links, so may be relevant.
Fuel trim refers to feedback compensation value compared against basic injection time. Fuel trim includes short-term and long-term fuel trim.
DTC P0171 is set when fuel trim is driven rich beyond a certain value. Possible causes are:
- Air induction system malfunction.
- Fuel injector restricted.
- Defective Manifold Absolute Pressure (MAP) sensor.
- Defective Engine Coolant Temperature (ECT) sensor.
- Improper fuel pressure.
- Exhaust system leak.
- Heated oxygen sensor No. 1 circuit is open or shorted.
- Defective heated oxygen sensor No. 1.
- Defective ECM.
DTC P0172 is set when fuel trim is driven lean beyond a certain value. Possible causes are:
- Fuel injector restricted or leaking.
- Defective Manifold Absolute Pressure (MAP) sensor.
- Defective Engine Coolant Temperature (ECT) sensor.
- Ignition system malfunction.
- Improper fuel pressure.
- Exhaust system leak.
- Heated oxygen sensor No. 1 circuit is open or shorted.
- Defective heated oxygen sensor No. 1.
- Defective ECM.