DTC P0172 [L8, LF]

id0102b1818500

DTC P0172

Fuel trim system too rich
DETECTION CONDITION
•  The PCM monitors short fuel trim (SHRTFT) and long fuel trim (LONGFT) values when closed loop fuel control. If the LONGFT and the sum total of these fuel trims or the SHRTFT exceed preprogrammed criteria, the PCM determines that the fuel system is too rich.
Diagnostic support note
•  This is a continuous monitor (fuel system).
•  The MIL illuminates if PCM detects above malfunction condition in two consecutive drive cycles or in one drive cycle while DTC for the same malfunction has been stored in PCM.
•  PENDING CODE is available if PCM detects the above malfunction condition during first drive cycle.
•  FREEZE FRAME DATA (Mode 2/Mode 12) is available.
•  The DTC is stored in the PCM memory.
POSSIBLE CAUSE
•  Erratic signal to PCM
―  APP sensor signal malfunction
―  ECT sensor signal malfunction
―  MAF sensor signal malfunction
―  TP sensor signal malfunction
―  VSS signal malfunction
•  A/F sensor heater malfunction
•  A/F sensor malfunction
―  A/F sensor looseness
―  Leakage exhaust system
―  A/F sensor deterioration
•  Air suction in intake air system
•  MAF sensor malfunction
•  Improper operation of purge solenoid valve
―  Purge solenoid valve malfunction (stuck open)
―  Purge solenoid hoses improper connection
•  Improper operation of EGR valve
•  Improper operation of variable tumble control system
•  Improper operation of variable valve timing control system improper operation
•  Fuel supply system malfunction or improper fuel line pressure
―  Pressure regulator (built-in fuel pump unit) malfunction
―  Fuel pump unit malfunction
―  Fuel filter clogged or restricted
―  Fuel leakage on fuel line from fuel distributor and fuel pump
•  Ignition system malfunction
―  Ignition coil related wiring harness malfunction
―  Ignition coil malfunction
―  Spark plug malfunction
•  Improper operation of fuel injector
―  Fuel injector malfunction
―  Fuel injector related wiring harness malfunction
•  PCV valve malfunction
•  Misfire
•  PCM malfunction

Diagnostic procedure

STEP

INSPECTION

ACTION
1
IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA (MODE 2)
•   Is the DTC P0172 on FREEZE FRAME DATA (Mode 2)?
Yes
Go to the next step.
No
Go to the troubleshooting procedures for DTC on FREEZE FRAME DATA (Mode 2).
(See DTC TABLE [L8, LF].)
2
VERIFY FREEZE FRAME DATA (MODE 12) AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED
•  Have the FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS (fuel system related) been recorded?
Yes
Go to the next step.
No
Record the FREEZE FRAME DATA (Mode 12) 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 STORED DTC
•  Turn the ignition switch off, then to the ON position (Engine off).
•  Verify related PENDING CODE and stored DTC.
•  Are any 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 not:
•  Go to the next step.
5
VERIFY CURRENT INPUT SIGNAL STATUS (KEY TO ON/IDLE)
•  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 switch is turned to the ON position and the engine runs?
Yes
Inspect the suspected circuit.
•  If the inspection results are normal:
―  Go to the next step.
•  If the inspection results are not normal:
―  Repair or replace the malfunctioning part according to the inspection results, then go to Step 21.
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.
•  Inspect the same PIDs as in Step 5 while simulating FREEZE FRAME DATA (Mode 2) condition.
•  Is there any signal which causes drastic changes?
Yes
Inspect the suspected circuit.
•  If the inspection results are normal:
―  Go to the next step.
•  If the inspection results are not normal:
―  Repair or replace the malfunctioning part according to the inspection results, then go to Step 21.
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 21.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [L8, LF].)
No
Go to the next step.
8
INSPECT A/F SENSOR
•  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 if the A/F sensor is loosely installed.
•  Is the A/F sensor installed securely?
Yes
Go to the next step.
No
Retighten the A/F sensor, then go to Step 21.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [L8, LF].)
10
INSPECT GAS LEAKAGE FROM EXHAUST SYSTEM
•  Visually inspect if there is any gas leakage between the exhaust manifold and A/F sensor.
•  Is there gas leakage?
Yes
Repair or replace any malfunctioning exhaust part, then go to Step 21.
No
Replace the A/F sensor, then go to Step 21.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [L8, LF].)
11
INSPECT MAF PID
•  Start the engine.
•  Access the MAF PID using the M-MDS.
•  Race the engine and verify that the MAF PID changes quickly according to change in the engine speed.
•  Is the MAF PID response normal?
Yes
Go to the next step.
No
Replace the MAF/IAT sensor, then go to Step 21.
(See MASS AIR FLOW (MAF)/INTAKE AIR TEMPERATURE (IAT) SENSOR REMOVAL/INSTALLATION [L8, LF].)
12
INSPECT PURGE SOLENOID VALVE OPERATION
•  Carry out the Purge Control System Inspection.
•  Does the purge control system work properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results, then go to Step 21.
13
INSPECT EGR VALVE OPERATION
•  Carry out the EGR Control System Inspection.
•  Does the EGR valve work properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results, then go to Step 21.
14
INSPECT VARIABLE TUMBLE CONTROL OPERATION
•  Carry out the Variable Tumble Control Operation Inspection.
•  Does variable tumble control system work properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results, then go to Step 21.
15
INSPECT VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION
•  Carry out the Variable Valve Timing Control System Operation Inspection.
•  Does variable valve timing control system work properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results, then go to Step 21.
16
INSPECT FUEL LINE PRESSURE
•  Turn the ignition switch off.
•  Inspect the fuel line pressure while the engine running.
•  Is fuel line pressure normal?
Yes
Go to Step 18.
No
If the fuel line pressure is too low:
•  Go to the next step.
If the fuel line pressure is excess high:
•  Replace the fuel pump unit, then go to Step 21.
17
INSPECT FUEL LINE FROM FUEL PUMP TO FUEL DISTRIBUTOR
•  Visually inspect the fuel line for fuel leakage.
•  Is there any fuel leakage?
Yes
Repair or replace the malfunctioning part according to the inspection results, then go to Step 21.
No
Inspect fuel filters for the foreign materials or stain inside fuel filter (low-pressure side).
Perform the following actions according to the inspection results:
•  If the foreign materials or stain is found inside fuel filter (low-pressure side):
―  Clean the fuel tank and filter (low-pressure side).
•  If normal:
―  Replace the fuel pump unit.
Go to Step 21.
18
INSPECT IGNITION SYSTEM OPERATION
•  Carry out the Spark Test.
•  Is the 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 21.
19
INSPECT FUEL INJECTOR OPERATION
•  Perform the Fuel Injector Operation Inspection.
•  Do the fuel injectors operate normally?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to the inspection results, then go to Step 21.
20
INSPECT PCV VALVE OPERATION
•  Inspect the PCV valve operation.
•  Is there any malfunction?
Yes
Replace the PCV valve, then go to the next step.
(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION [L8, LF].)
No
Go to the next step.
21
VERIFY TROUBLESHOOTING OF DTC P0172 COMPLETED
•  Make sure to reconnect all disconnected connectors.
•  Clear the DTC from the PCM memory using the M-MDS.
•  Perform the Drive Mode 03 (PCM Adaptive Memory Production, EGR System, A/F Sensor Heater, HO2S Heater, A/F Sensor, HO2S, and TWC Repair Verification Drive Mode).
•  Is the PENDING CODE for this DTC present?
Yes
Replace the PCM, then go to the next step.
(See PCM REMOVAL/INSTALLATION [L8, LF].)
No
Go to the next step.
22
VERIFY AFTER REPAIR PROCEDURE
•  Perform the “AFTER REPAIR PROCEDURE”.
•  Are any DTCs present?
Yes
Go to the applicable DTC inspection.
(See DTC TABLE [L8, LF].)
No
DTC troubleshooting completed.