Description
The fuel trim is related to the feedback compensation value, not to the basic injection time. The fuel trim consists of both the short-term and the long-term fuel trims.
The short-term fuel trim is fuel compensation that is used to constantly maintain the air-fuel ratio at stoichiometric levels. The signal from the air-fuel ratio (a/f) sensor indicates whether the air-fuel ratio is rich or lean compared to the stoichiometric ratio. This triggers a reduction in the fuel injection volume if the air-fuel ratio is rich and an increase in the fuel injection volume if it is lean.
Factors such as individual engine differences, wear over time and changes in operating environment cause short-term fuel trim to vary from the central value. The long-term fuel trim, which controls overall fuel compensation, compensates for long-term deviations in the fuel trim from the central value caused by the short-term fuel trim compensation.
If both the short-term and long-term fuel trims are lean or rich beyond predetermined values, it is interpreted as a malfunction, and the ecm illuminates the mil and sets a dtc.
Hint:
Monitor description
Under closed-loop fuel control, fuel injection volumes that deviate from those estimated by the ecm cause changes in the long-term fuel trim compensation value. The long-term fuel trim is adjusted when there are persistent deviations in the short-term fuel trim values. Deviations from the ecm's estimated fuel injection volumes also affect the average fuel trim learning value, which is a combination of the average short-term fuel trim (fuel feedback compensation value) and the average long-term fuel trim (learning value of the air-fuel ratio). If the average fuel trim learning value exceeds the malfunction threshold, the ecm interprets this as a fault in the fuel system and sets a dtc.
Example: the average fuel trim learning value is +35 % or more or -35 % or less, the ecm interprets this as a fuel system malfunction.
Monitor strategy
Typical enabling conditions
Typical malfunction thresholds
Wiring diagram
Refer to dtc p2195 (see page es-296).
Inspection procedure
Hint:
Hint:
If any dtcs other than p0171 or p0172 are output, troubleshoot those dtcs first.
Result: the a/f sensor reacts in accordance with increases and decreases in the fuel injection volume: +25 % = rich output: less than 3.0 V -12.5 % = Lean output: more than 3.35 V
Notice:
The a/f sensor has an output delay of a few seconds and the ho2 sensor has a maximum output delay of approximately 20 seconds.
Following the a/f control procedure enables technicians to check and graph the voltage outputs of both the a/f and ho2 sensors.
To display the graph, select the following menu items on the tester: diagnosis / enhanced obd ii / active test / a/f control / user data / afs b1s1 and o2s b1s2; then press the yes button and then the enter button followed by the f4 button.
Standard: maf while engine idling: between 1 g/sec. And 3 g/ sec. (Shift position: n, a/c: off).
Maf at engine speed of 2,500 rpm: between 2 g/ sec. And 6 g/sec. (Shift position: n, a/c: off).
Standard: with cold engine: same as ambient air temperature.
With warm engine: between 75°c and 100°c (167°f and 212°f).
Ok:
Pcv hose is connected correctly and is not damaged.
Ok: no leakage from air induction system.
Ok: no gas leakage.
Standard pressure: 304 to 343 kpa (3.1 To 3.5 Kgf/cm2, 44.1 To 49.7 Psi)
Standard injection volume: 45 to 58 cm3 (2.9 To 3.5 Cu in.) Per 15 seconds
Hint:
If the system is still malfunctioning, the mil will be illuminated during step (f).
Notice:
If the conditions in this test are not strictly followed, no malfunction will be detected.
Outside vehicle
General maintenance
Performing the following maintenance checks on the vehicle
is the owner's responsibility. The owner may perform the
maintenance or take the vehicle to a service center. Check
the parts of the vehicle described below on a daily basis. In
most cases, special tools are not requ ...
Identification information
Vehicle identification and serial numbers
Vehicle identification number
The vehicle identification number is stamped on the
vehicle identification number plate and on the
certification label, as shown in the illustrations.
Vehicle identification number plate
Certification label ...
Low battery positive voltage
Description
When there is an abnormality in the power supply circuit of the brake
actuator (skid control ecu), the skid
control ecu sets a dtc and the operation is prohibited by the fail-safe
function. This dtc is set when the
voltage supplied to terminal ig1 is outside the dtc detection ...