DTC P0171:00 [MZR 1.3, MZR 1.5]

id0102f8934200

DTC P0171:00

Fuel trim system too lean
DETECTION CONDITION
•  The PCM monitors short term fuel trim (SHRTFT) and long term fuel trim (LONGFT) values when closed loop fuel control. If the LONGFT and the sum total of these fuel trims exceed preprogrammed criteria, the PCM determines that the fuel system is too lean.
Diagnostic support note
•  This is a continuous monitor (fuel system).
•  The MIL illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.
•  PENDING CODE is available if the PCM detects the above malfunction condition during first drive cycle.
•  FREEZE FRAME DATA (Mode 2)/Snapshot data is available.
•  The DTC is stored in the PCM memory.
POSSIBLE CAUSE
•  Misfire
•  Erratic signal to PCM
―  APP sensor signal malfunction
―  ECT sensor signal malfunction
―  MAF sensor signal malfunction
―  TP sensor signal malfunction
―  VSS signal malfunction
―  Related connector or terminals malfunction
―  Related wiring harness malfunction
•  A/F sensor heater malfunction
•  A/F sensor malfunction
―  A/F sensor looseness
―  Exhaust system leakage
―  A/F sensor deterioration
•  Air suction in intake-air system
•  MAF sensor malfunction
•  Improper operation of purge control system
•  Improper operation of variable valve timing control system
•  Fuel supply system malfunction
―  Pressure regulator malfunction (built-into fuel pump unit)
―  Fuel pump malfunction
―  Fuel leakage in fuel line between fuel distributor and fuel pump
―  Fuel filter restricted
―  Fuel return hose restricted
•  Ignition system malfunction
―  Ignition coil related wiring harness malfunction
―  Spark plug malfunction
―  Ignition coil malfunction
•  Insufficient engine compression
•  Improper operation of fuel injector
•  PCM malfunction

Diagnostic procedure

STEP

INSPECTION

ACTION
1
IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA (MODE 2)
•  Perform the Freeze Frame PID Data Access Procedure.
•  Is the DTC P0171:00 on FREEZE FRAME DATA (Mode 2)?
Yes
Go to the next step.
No
Go to the troubleshooting procedure for DTC on FREEZE FRAME DATA (Mode 2).
(See DTC TABLE [MZR 1.3, MZR 1.5].)
2
VERIFY FREEZE FRAME DATA (MODE 2)/SNAPSHOT DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED
•  Have the FREEZE FRAME DATA (Mode 2)/snapshot data and DIAGNOSTIC MONITORING TEST RESULTS (fuel system related) been recorded?
Yes
Go to the next step.
No
Record the FREEZE FRAME DATA (Mode 2)/snapshot data and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.
3
VERIFY RELATED SERVICE INFORMATION AVAILABILITY
•  Verify related Service Information availability.
•  Is any related Service Information available?
Yes
Perform repair or diagnosis according to the available Service Information.
•  If the vehicle is not repaired, go to the next step.
No
Go to the next step.
4
VERIFY RELATED PENDING CODE AND/OR DTC
•  Turn the ignition switch off, then to the ON position (engine off).
•  Perform the Pending Trouble Code Access Procedure and DTC Reading Procedure.
•  Are any other PENDING CODEs and/or DTCs present?
Yes
If misfire DTC is present:
•  Go to Step 11.
If other DTC is present:
•  Go to the applicable DTC inspection.
No
If drive ability concern is present:
•  Go to Step 11.
If drive ability concern is not present:
•  Go to the next step.
5
VERIFY CURRENT INPUT SIGNAL STATUS
•  Access the following PIDs using the M-MDS.
―  APP1
―  APP2
―  ECT
―  MAF
―  TP REL
―  VSS
•  Is there any signal that is far out of specification when the ignition is switched to ON and the engine runs?
Yes
Inspect the suspected sensor and related wiring harness.
Repair or replace the malfunctioning part according to the inspection results, then go to Step 20.
No
Go to the next step.
6
VERIFY CURRENT INPUT SIGNAL STATUS UNDER FREEZE FRAME DATA (MODE 2) CONDITION
Caution
•  While performing this step, always operate the vehicle in a safe and lawful manner.
•  When the M-MDS is used to observe monitor system status while driving, be sure to have another technician with you, or record the data in the M-MDS using the PID/DATA MONITOR AND RECORD capturing function and inspect later.
•  Access the same PIDs as in Step 5 while simulating under the FREEZE FRAME DATA (Mode 2) condition.
•  Is there any signal which causes drastic changes?
Yes
Inspect the suspected sensor and related wiring harness.
Repair or replace the malfunctioning part according to the inspection results, then go to Step 20.
No
Go to the next step.
7
INSPECT A/F SENSOR HEATER
•  Inspect the A/F sensor heater.
•  Is there any malfunction?
Yes
Replace the A/F sensor, then go to Step 20.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [MZR 1.3, MZR 1.5].)
No
Go to the next step.
8
INSPECT CURRENT INPUT SIGNAL STATUS OF A/F SENSOR
•  Reconnect all disconnected connectors.
•  Inspect the A/F sensor.
•  Is there any malfunction?
Yes
Go to the next step.
No
Go to Step 11.
9
INSPECT INSTALLATION OF A/F SENSOR
•  Inspect installation of A/F sensor.
•  Is the A/F sensor installed securely?
Yes
Go to the next step.
No
Retighten the A/F sensor, then go to Step 20.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [MZR 1.3, MZR 1.5].)
10
INSPECT FOR LEAKAGE FROM EXHAUST SYSTEM
•  Visually inspect for exhaust gas leakage between exhaust manifold and A/F sensor.
•  Is there any leakage?
Yes
Repair or replace the malfunctioning part according to the inspection results, then go to Step 20.
No
Replace the A/F sensor, then go to Step 20.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [MZR 1.3, MZR 1.5].)
11
VERIFY CURRENT INPUT SIGNAL STATUS OF MAF SENSOR
•  Start the engine.
•  Access the MAF PID using the M-MDS.
•  Verify that the MAF PID value changes quickly while increasing (racing) the engine speed.
•  Is the MAF PID value normal?
Yes
Go to Step 13.
No
Go to the next step.
12
INSPECT FOR EXCESSIVE AIR SUCTION OF INTAKE-AIR SYSTEM
•  Visually inspect for loose, cracked or damaged hoses on the intake-air system.
Note
•  Engine speed may change when rust penetrating agent is sprayed on the air suction area.
•  Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results, then go to Step 20.
No
Replace the MAF/IAT sensor, then go to Step 20.
(See MASS AIR FLOW (MAF)/INTAKE AIR TEMPERATURE (IAT) SENSOR REMOVAL/INSTALLATION [MZR 1.3, MZR 1.5].)
13
INSPECT PURGE CONTROL SYSTEM OPERATION
•  Perform the Purge Control System Inspection.
•  Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results, then go to Step 20.
No
Go to the next step.
14
INSPECT VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION
•  Perform the Variable Valve Timing Control System Operation Inspection.
•  Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results, then go to Step 20.
No
Go to the next step.
15
INSPECT FUEL LINE PRESSURE
•  Turn the ignition switch off.
Note
•  If the engine will not start, inspect the fuel line pressure with ignition switches to ON.
•  Inspect the fuel line pressure with the engine is running.
•  Is there any malfunction?
Yes
If the fuel line pressure is too low:
•  Go to the next step.
If the fuel line pressure is too high:
•  Replace the fuel pump unit, then go to Step 20.
No
Go to Step 17.
16
INSPECT FUEL LINE LEAKAGE
•  Visually inspect for leakage from fuel line between fuel distributor and fuel pump.
•  Is there any leakage?
Yes
Repair or replace the malfunctioning part according to the inspection results, then go to Step 20.
No
Visually inspect for foreign materials or stain inside fuel filter (low-pressure side).
•  If there is any malfunction:
―  Clean the fuel tank and filter (low-pressure side).
•  If there is no malfunction:
―  Replace the fuel pump unit.
Go to Step 20.
17
INSPECT IGNITION SYSTEM OPERATION
•  Perform the Spark Test.
•  Is a strong blue spark visible at each cylinder?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results, then go to Step 20.
18
INSPECT ENGINE COMPRESSION
•  Inspect the engine compression.
•  Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results, then go to Step 20.
No
Go to the next step.
19
INSPECT FUEL INJECTOR OPERATION
•  Perform the Fuel Injector Operation Inspection.
•  Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results, then go to the next step.
(See FUEL INJECTOR REMOVAL/INSTALLATION [MZR 1.3, MZR 1.5].)
No
Go to the next step.
20
VERIFY DTC TROUBLESHOOTING COMPLETED
•  Make sure to reconnect all disconnected connectors.
•  Clear the DTC from the PCM memory using the M-MDS.
•  Perform the Drive Mode 03 (A/F Sensor Heater, HO2S Heater, A/F Sensor, HO2S and TWC Repair Verification Drive Mode).
•  Stop the vehicle and access the ON BOARD READINESS TEST to inspect Drive Mode completion status.
•  Verify the FUEL_EVAL PID changes to yes.
―  If not, perform the Drive Mode 03 (A/F Sensor Heater, HO2S Heater, A/F Sensor, HO2S and TWC Repair Verification Drive Mode).
•  Perform the KOER self test.
•  Is the PENDING CODE for this DTC present?
Yes
Repeat the inspection from Step 1.
•  If the malfunction recurs, replace the PCM.
Go to the next step.
No
Go to the next step.
21
VERIFY AFTER REPAIR PROCEDURE
•  Perform the “AFTER REPAIR PROCEDURE”.
•  Are any DTCs present?
Yes
Go to the applicable DTC inspection.
(See DTC TABLE [MZR 1.3, MZR 1.5].)
No
DTC troubleshooting completed.