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 heated oxygen sensor indicates whether the air–fuel ratio is RICH or
LEAN compared to the ideal theoretical value, triggening 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.
HINT;
•
When DTC P0171 is recorded, the actual air–fuel ratio is on the LEAN side. When DTC P0172 is
recorded, the actual air–fuel ratio is on the RICH side,
•
Fuel trim applies separately to bank 1 and bank 2, so the ECM lights up the MIL if a problem occurs with
either bank.
•
You can tell which bank is malfunctioning by looking at the short–term fuel trim and long–term fuel trim,
thus allowing you to focus your inspection.
•
If the total of the short–term fuel trim value and long–term fuel trim value for each bank is within
±
25%, the system is functioning normally.
•
Air intake (hose loose)
•
Fuel line pressure
•
Injector blockage
•
Heated oxygen sensor malfunction
•
Mass air flow meter
•
Engine coolant temp. sensor
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)
When the air fuel ratio feedback is stable after
engine warming up, the fuel trim is considerably in
error on the LEAN side.
(2 trip detection logic)
•
Fuel line pressure
•
Injector leak, blockage
•
Heated oxygen sensor malfunction
•
Mass air flow meter
•
Engine coolant temp. sensor
Diagnostic Trouble Code Detecting Condition
Trouble Area
DTC P0171 System too Lean (Fuel Trim)
DTC P0172 System too Rich (Fuel Trim)
DTC No.
P0172
P0171
–
1MZ–FE ENGINE
CIRCUIT INSPECTION
EG2–486
Summary of Contents for 1 MZ-FE
Page 1: ...1MZ FE ENGINE 1MZ FE ENGINE EG2 1 ...
Page 22: ...Adjusting Shim Selection Chart Intake 1MZ FE ENGINE ENGINE MECHANICAL EG2 22 ...
Page 23: ...Adjusting Shim Selection Chart Exhaust 1MZ FE ENGINE ENGINE MECHANICAL EG2 23 ...
Page 39: ...TIMING BELT COMPONENTS FOR REMOVAL AND INSTALLATION 1MZ FE ENGINE ENGINE MECHANICAL EG2 39 ...
Page 40: ... 1MZ FE ENGINE ENGINE MECHANICAL EG2 40 ...
Page 57: ...CYLINDER HEAD COMPONENTS FOR REMOVAL AND INSTALLATION 1MZ FE ENGINE ENGINE MECHANICAL EG2 57 ...
Page 58: ... 1MZ FE ENGINE ENGINE MECHANICAL EG2 58 ...
Page 59: ... 1MZ FE ENGINE ENGINE MECHANICAL EG2 59 ...
Page 60: ... 1MZ FE ENGINE ENGINE MECHANICAL EG2 60 ...
Page 61: ... 1MZ FE ENGINE ENGINE MECHANICAL EG2 61 ...
Page 122: ... 1MZ FE ENGINE ENGINE MECHANICAL EG2 122 ...
Page 123: ... 1MZ FE ENGINE ENGINE MECHANICAL EG2 123 ...
Page 135: ...COMPONENTS FOR PREPARATION AND AFTER ASSEMBLY 1MZ FE ENGINE ENGINE MECHANICAL EG2 135 ...
Page 189: ...EXHAUST SYSTEM COMPONENTS 1MZ FE ENGINE ENGINE MECHANICAL EG2 189 ...
Page 197: ...COMPONENT LAYOUT 1MZ FE ENGINE EMISSION CONTROL SYSTEMS EG2 197 ...
Page 198: ...SCHEMATIC DRAWING 1MZ FE ENGINE EMISSION CONTROL SYSTEMS EG2 198 ...
Page 217: ...SFI SYSTEM DESCRIPTION 1MZ FE ENGINE SFI SYSTEM EG2 217 ...
Page 219: ...SYSTEM CIRCUIT 1MZ FE ENGINE SFI SYSTEM EG2 219 ...
Page 245: ...COMPONENTS FOR REMOVAL AND INSTALLATION 1MZ FE ENGINE SFI SYSTEM EG2 245 ...
Page 258: ...FUEL TANK AND LINE COMPONENTS 1MZ FE ENGINE SFI SYSTEM EG2 258 ...
Page 284: ...COMPONENTS FOR REMOVAL AND INSTALLATION 1MZ FE ENGINE SFI SYSTEM EG2 284 ...
Page 288: ...COMPONENTS FOR REMOVAL AND INSTALLATION 1MZ FE ENGINE SFI SYSTEM EG2 288 ...
Page 290: ...1MZ FE ENGINE Memo ...
Page 292: ...COMPONENTS FOR REMOVAL AND INSTALLATION 1MZ FE ENGINE SFI SYSTEM EG2 292 ...
Page 299: ...KNOCK SENSOR COMPONENTS FOR REMOVAL AND INSTALLATION 1MZ FE ENGINE SFI SYSTEM EG2 299 ...
Page 309: ...1MZ FE ENGINE Memo ...
Page 320: ...WATER PUMP COMPONENTS FOR REMOVAL AND INSTALLATION 1MZ FE ENGINE COOLING SYSTEM EG2 320 ...
Page 321: ... 1MZ FE ENGINE COOLING SYSTEM EG2 321 ...
Page 335: ...COMPONENTS FOR REMOVAL AND INSTALLATION 1MZ FE ENGINE COOLING SYSTEM EG2 335 ...
Page 351: ...Hydraulic Motor COMPONENTS FOR REMOVAL AND INSTALLATION 1MZ FE ENGINE COOLING SYSTEM EG2 351 ...
Page 374: ...OIL PUMP COMPONENTS FOR REMOVAL AND INSTALLATION 1MZ FE ENGINE LUBRICATION SYSTEM EG2 374 ...
Page 375: ... 1MZ FE ENGINE LUBRICATION SYSTEM EG2 375 ...
Page 376: ... 1MZ FE ENGINE LUBRICATION SYSTEM EG2 376 ...
Page 394: ...1MZ FE ENGINE TROUBLESHOOTING 1MZ FE ENGINE EG2 394 ...
Page 395: ... 1MZ FE ENGINE EG2 395 ...
Page 423: ...PARTS LOCATION 1MZ FE ENGINE PARTS LOCATION EG2 423 ...
Page 424: ...WIRING DIAGRAM 1MZ FE ENGINE WIRING DIAGRAM EG2 424 ...
Page 425: ... 1MZ FE ENGINE WIRING DIAGRAM EG2 425 ...
Page 429: ... MEMO 1MZ FE ENGINE EG2 429 ...
Page 442: ...Location of Connectors in Body 1MZ FE ENGINE LOCATION OF CONNECTORS EG2 442 ...
Page 443: ...Fuel Pump Wagon 1MZ FE ENGINE LOCATION OF CONNECTORS EG2 443 ...
Page 452: ...WIRING DIAGRAM 1MZ FE ENGINE CIRCUIT INSPECTION EG2 452 ...
Page 464: ...WIRING DIAGRAM 1MZ FE ENGINE CIRCUIT INSPECTION EG2 464 ...
Page 494: ...WIRING DIAGRAM 1MZ FE ENGINE CIRCUIT INSPECTION EG2 494 ...
Page 518: ...WIRING DIAGRAM 1MZ FE ENGINE CIRCUIT INSPECTION EG2 518 ...
Page 576: ...WIRING DIAGRAM 1MZ FE ENGINE CIRCUIT INSPECTION EG2 576 ...