The fuel trim is related to the feedback compensation value, not to the basic injection time. The fuel trim includes the short–term fuel trim and the long–term fuel trim.
The short–term fuel trim is the short–term fuel compensation used to maintain the air–fuel ratio at stoichiometric air–fuel ratio. The signal from the heated oxygen sensor indicates whether the air–fuel ratio is rich or lean compared to the stoichiometric air–fuel ratio. This variance triggers a reduction in the fuel volume if the air–fuel ratio is rich, and an increase in the fuel volume if it is lean.
The long–term fuel trim is the overall fuel compensation carried out in long–term to compensate for a continual deviation of the short–term fuel trim from the central value, due to individual engine differences, wear overtime and changes in the operating environment.
If both the short–term fuel trim and the long–term fuel trim are lean or rich beyond a certain value, it is detected as a malfunction and the mil is illuminated.
Dtc no. |
Dtc detection condition |
Trouble area |
P0171 | When air–fuel ratio feedback is stable after warming up engine, fuel trim is considerably in error on lean side (2 trip detection logic) |
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P0172 | When air–fuel ratio feedback is stable after warming up engine, fuel trim is considerably in error on rich side (2 trip detection logic) |
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Hint
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Monitor description
Under the closed–loop fuel control, fuel injection amounts that deviate from the ecm’s estimated fuel amount will cause a change in the long–term fuel trim compensation value. This long–term fuel trim is adjusted when there are persistent deviations in the short–term fuel trim values. And the deviation from a simulated fuel injection amount by the ecm affects a smoothed fuel trim learning value which is the combination of smoothed short–term fuel trim (fuel feedback compensation value) and smoothed long–term fuel trim (learning value of the air–fuel ratio). When the smoothed fuel trim learning value exceeds the dtc threshold, the ecm interprets this as a fault in the fuel system and sets a dtc.
Example: the smoothed fuel trim leaning value is more than +35% or less than –35%, the ecm interprets this as a fail in the fuel system.
Monitor strategy
Typical enabling conditions
Typical malfunction thresholds
Wiring diagram
Refer to dtc p0130
Floor shift cable transmission control shift
Replacement
Hint: components:
1. Remove air conditioner unit assy
Hint:
refer to the instructions for removal of the air conditioner unit assy.
2. Separate air bag sensor assy center
remove the 3 bolts, separate the airbag sensor assy center.
3. Remove exhaust pipe assy
4. Remo ...
Inspection procedure
1 Check airbag sensor assy center connector
Disconnect negative (–) terminal cable from the battery, and wait at
least for 90 seconds.
check the connection of the airbag sensor assy center connectors.
2 Check air bag sensor assy center
Sst 09843–18040
Connect the negat ...
Inspection
1. Windshield wiper switch assy
Continuity check
check the continuity of each terminal of the connector.
Front wiper switch
Standard:
Front washer switch
Standard:
W/o intermittent time adjust:
intermittent operation check
connect the voltmeter (+) te ...