Yaris CDX 1999 P0171 error code

[Davax]

Hi to all at Yaris World.
My Yaris CDX 1999 model had the CEL come on twice in a week. The code reader states it is P0171 - Adaptive fuel too lean -Bank 1.
About 2 weeks ago I noticed that the idle speed was about 550 rpm so I cleaned the Maf sensor, trottle body. I did not remove the Idle Control Valve since I did not have a gasket. I also added a fuel additive (Lucas) to clean the fuel system. The idle speed still remained the same so I adjusted the Idle Screw. So the above are not the cause. Now I checked the vacuum pipes from the canister. All seem OK. My daughter is using this car to learn to drive and since she is new at driving she frequently knockes the vehicle when releasing the clutch. I have noticed that the CEL is coming on a day after she goes driving. Could this have to do with the CEL coming on. Here under are the Code reader/Scanner readings.
All technical advice would be greatly appreciated.



MIL Status

MIL Status On
Misfire Monitor OK
Fuel System Mon Ok
Comp. Component OK
Catalyst Mon OK
Htd Catalyst n/a
Evap System Mon n/a
Sec Air System n/a
O2 Sens Mon OK
O2 Sen Htr OK
Efr System n/a


Trouble Codes

Codes Totals 02
Fault Codes 01
Pend Codes 01

P0171 - 01/02 - Generic System Too Lean (Bk 1)
P0171 - 02/02 - Generic System Too Lean (Bk 1)

Freeze Frame

Trouble code P0171
Fuel Sys 1 n/a
Fuel Sys 2 n/a
Calc Load (%) 35.6
Coolant (°F) 183
ST FTRM1 (%) 0.7
LT FTRM1 (%) 29.6
Engine (RPM) 2270
Veh speed (MPH) 40
IAT (°F) 102

Live Data (at Idle)

Fuel Sys 1 cl, using HO2S
Fuel Sys 2 cl. Using HO2S
Coolant (°F) 187
ST FTRM1 (%) -1.5 to -4.6
LT FTRM1 (%) 3.8
Engine (Rpm) 652
Veh Speed (Mph) 0
Ign adv (deg) 8.0 to 9.5
IAT (°F) 129
MAF (lb/min) 0.134
ABSLT TPS (%) 10.9
O2S11 (V) (%)
0.085 to 0.705 -2.3 to -3.9
O2S12 (V) (%)
0.72 to 0.75 n/a

[smikutel]

what kind of code scanner are you using ?

[smikutel]

have you ruled out bad gas too much alcohol or water in the gas or clogged fuel injectors ?


Just a WAG (Wild Ass Guess) method deduction.