CIRCUIT DESCRIPTION Fuel trim refers to the feedback compensation value compared against the basic injection time. Fuel trim includes short-term fuel trim and long-term fuel trim. Short-term fuel trim is the short-term fuel compensation used to maintain the air-fuel ratio at its ideal theoretical value. The signal from the oxygen sensor indicates whether the air-fuel ratio is RICH or LEAN compared to the ideal theoretical value, triggering a reduction in fuel volume if the air-fuel ratio is rich, and an increase in fuel volume if it is lean. Long-term fuel trim is overall fuel compensation carried out long-term to compensate for continual deviation of the short-term fuel trim from the central value due to individual engine differences, wear over time and changes in the usage environment. If both the short-term fuel trim and long-term fuel trim are LEAN or RICH beyond a certain value, it is detected as a malfunction and the MIL lights up. DTC No.
P0171
DTC Detecting Condition
Trouble Area
When the air-fuel ratio feedback is stable after engine warming up, the fuel trim is considerably in error on the RICH side (2 trip detection logic)
Air induction system Injector blockage Mass air flow meter Engine coolant temp. sensor Fuel pressure Gas leakage on exhaust system Open or short in heated oxygen sensor (bank 1 sensor 1) circuit Heated oxygen sensor (bank 1 sensor 1) PCV piping
HINT:
If the vehicle runs out of fuel, the air-fuel ratio is LEAN and DTC P0171 is recorded. The MIL then comes on. If the total of the short-term fuel trim value and long-term fuel trim value is within ± 38 %, the system is functioning normally. The oxygen sensor output voltage and the short-term fuel trim value can be read using the OBD II scan tool or TOYOTA hand-held tester.
INSPECTION PROCEDURE HINT: Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool. Because freeze frame records the engine conditions when the malfunction is detected, when troubleshooting it is useful for determining whether the vehicle was running or stopped, the engine warmed up or not, the air-fuel ratio lean or rich, etc. at the time of the malfunction.
1
Check air induction system (See page SF-1 ).
NG
Repair or replace.
OK 2002 ECHO (RM884U)
Author:
Date:
229
DI-60 DIAGNOSTICS
2
-
ENGINE
Check connection of PCV piping.
NG
Repair or replace PCV piping.
OK
3
Check injector injection (See page SF-21 ).
NG
Replace injector.
OK
4
Check mass air flow meter and engine coolant temp. sensor (See page SF-30 , SF-54 ).
NG
Repair or replace.
OK
5
Check for spark and ignition (See page IG-1 ).
NG
Repair or replace.
OK
6
Check fuel pressure (See page SF-6 ).
NG
Check and repair fuel pump, pressure regulator, fuel pipe line and filter.
OK
2002 ECHO (RM884U)
Author:
Date:
230
DI-61 DIAGNOSTICS
7
-
ENGINE
Check gas leakade on exhaust system.
NG
Repair or replace.
OK
8
Check the output voltage of oxygen sensor during idling.
PREPARATION: Warm up the oxygen sensor the engine at 2,500 rpm for approx. 90 sec. CHECK: Use the OBD II scan tool or TOYOTA hand-held tester read the output voltage of the oxygen sensor during idling. OK: Oxygen sensor output voltage: Alternates repeatedly between less than 0.4 V and more than 0.55 V (See the following table).
P18349
OK
Go to step 10.
NG
2002 ECHO (RM884U)
Author:
Date:
231
DI-62 DIAGNOSTICS
9
-
ENGINE
Check for open and short in harness and connector between ECM and oxygen sensor (See page IN-19 ).
NG
Repair or replace harness or connector.
OK
Replace oxygen sensor.
10
Perform confirmation driving pattern (See page DI-48 ).
GO
11
Is there DTC P0171 being output again?
YES
Check and replace ECM (See page IN-29 ).
NO
12
Did vehicle runs out of fuel in the past?
NO
Check for intermittent problems.
YES
DTC P0171 or P0172 is caused by running out of fuel.
(c) Install the injector into the delivery pipe and cylinder ... Refer to the intelligent tester operator's manual .... Perform the inspection in a well-ventilated area.
flame in area when cleaning flame arrestor and crankcase ... being supplied to water pickup holes in gear housing or water pickup inlet, or water pump im-.
manual for an understanding of system operation, before troubleshooting ..... the future. NOTICE TO OWNER/OPERATOR. Your engine is equipped with special design features and ... signed so that modifications are not pos- sible. â¢. A durable ...
2. 1. R-W. R-B. ECM. OCV+. OCV-. 10. 23. E7. E7. DI-122. -. DIAGNOSTICS. ENGINE ... (b) Connect the TOYOTA hand-held tester and select VVT from ACTIVE TEST menu. CHECK: ... Replace oil control valve, and then go to step 6. OK. 6.
The rotary solenoid type IAC valve is located on the throttle body and intake air bypassing the throttle valve is directed to the IAC valve through a passage.
upwards (the emergency flasher button is part of the ring and will move with it so there will be a wire ... 5) Then here comes the tricky part the FOURTH screw.
The engine driven fuel pump outlet fitting (A) is drilled and tapped to provide a source for the .... system installation or the design of the individual ... calculation with a dipstick reading. (provided ... and ducting cooling air through it. b. En
Without a provision to cool the pump, va- por bubbles are formed at a rapid rate ... second electric pump of the continuous duty type, such as the Facet low ...
Aug 9, 2012 - My calculations show about 365 Ib./in' of vacuum will be required to draw the ... the lines should be drained so fuel will not dry leaving residue.
The following air systems have the following components (not including air tubes and hoses):. - Intake Air Shot Air .... BK BLACK. YEL YELLOW. BU ... BLUE. GRAN GREEN. RID... RED. WAT..WHITE. BRN. OR. LT8U ... Ignition system faulty (see Section 16).
Aug 9, 2012 - I know this statement makes you want to rush to the phone and notify your favorite tabloid ... independently by each tank which in turn feeds the electric boost pump. ... check valves), install a second sump, drain, fuel pickup and fuel
aircraft we test at the CAFE Foundation for Sport A viation had fuel ... CAFE Foundation. Fuel system vapor ... A large percentage of "carb ice" incidents are really ...
job. The office itself (desk, furniture, files, computer...) is often considered as private ... Management, which most known ... workshops, where methods and.
flammable - great care must be taken when working on any part of the fuel system. Do not smoke or allow any naked flames or uncovered light bulbs near the ...
After the engine is warmed up, oxygen sensor (bank 1 sensor. 1) output does not indicate RICH (y 0.45 V) even once when conditions (a), (b), and (c) continue ...
3.14 Anti-flooding device vacuum intake (Weber .... should be between 5.5 and 6.5 mm (0.22 and. 0.26 in) and .... be between 6.5 and 7.5 mm (0.26 and 0.30 in).
with no moving parts and a simple flat gasket where the cap meets the ... owners keep pipe cleaners (attached to. âremove ... designs on general aviation aircraft:.
While talking to Larry Burton of. Klamath Falls, OR about his fuel tanks in his Cavalier and the fuel pick up prob- lems long tanks cause, I discovered he.
During the descent, the pilot made a Mayday call advising that .... This is the inside of a wet wing fuel tank, with the fuel-sending unit in the center. You can see ...
Ensuite, 5 ans au sein du leader mondial en matière de sécurité numérique, en tant ... Effectuer une transformation Lean réussie, passe par l'implémentation ...
