Question about 2001 Toyota Corolla
DTC P0171 is set when fuel trim is driven rich beyond a certain value. Possible causes are:
1. Exhaust system leak.
2. Improper fuel pressure.
3. Fuel injector restricted.
4. Defective heated oxygen sensor No. 1.
5. Defective Manifold Absolute Pressure (MAP) sensor.
6. Defective Engine Coolant Temperature (ECT) sensor.
When the air fuel ratio feedback is stable after the engine is at operating temperature and the fuel trim has reached its limit of correction to the rich side. (2 trip logic).
Feedback from the HO 2 sensor influences short-term fuel trim and short-term fuel trim influences long trim fuel trim. Short-term values are temporary and not stored when the ignition key is turned off. Long-term values are stored in memory because they are part of the basic injection duration. Long term values affect injection duration in closed and open loop because they are used to calculate basic injection duration. It is important to remember that the actual fuel trim will be the opposite of the DTC. A system too lean, DTC P0171 will mean the ECM is making a + or rich correction.
read (and let me know)above data and Freeze Frame by using (example, generic) Scan Tool on # mode 2, etc.
Slowly accelerate the engine in the increments shown and record voltage,
grams/sec of MAF and SFT, LFT, Injection Pulse, Fuel Pressure, etc.
Vehicle have MAF Sensor?
Posted on Jan 03, 2011
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Posted on Jan 02, 2017
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