DTC P2178 [L8, LF]

id0102b1812400

DTC P2178

Fuel system too rich at off idle
DETECTION CONDITION
•  The PCM monitors short term fuel trim (SHRTFT), long term fuel trim (LONGFT) during closed loop fuel control at off-idle. If the LONGFT and the sum total of these fuel trims exceed preprogrammed criteria. The PCM determines that fuel system is too rich at off-idle.
Diagnostic support note
•  This is a continuous monitor (fuel system).
•  The MIL illuminates if the PCM detects the above malfunctioning 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 conditions during the 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
―  Exhaust system leakage
―  A/F sensor deterioration
•  MAF sensor malfunction
•  Purge system malfunction
―  Purge solenoid valve improper operation
―  Improper connection purge solenoid hose
―  Purge solenoid valve malfunction (stuck open)
•  Improper operation of EGR valve
•  Improper operation of variable tumble control
•  Improper operation of fuel injector
•  Fuel supply system malfunction or improper fuel line malfunction
―  Pressure regulator (built-in fuel pump unit) malfunction
―  Fuel leakage in fuel line between fuel distribution pipe and fuel pump
•  Ignition system malfunction
―  Ignition coil related wiring harness malfunction
―  Ignition coil malfunction
―  Spark plug malfunction
•  Improper operation of variable valve timing control system
•  Improper operation of PCV valve
•  Misfire
•  PCM malfunction

Diagnostic procedure

STEP

INSPECTION

ACTION
1
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 repair order, then go to the next step.
2
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.
3
VERIFY RELATED PENDING CODE AND STORED 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 DTCs present?
Yes
If misfire DTC is present:
•  Go to Step 11.
If other DTC is present:
•  Go to the applicable DTC troubleshooting.
No
If driveability concern is present:
•  Go to Step 11.
If not:
•  Go to the next step.
4
IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA (MODE 2)
•  Perform the Freeze Frame PID Data Access Procedure.
•  Is the DTC P2178 on FREEZE FRAME DATA (Mode 2)?
Yes
Go to the next step.
No
Go to the DTC troubleshooting on FREEZE FRAME DATA (Mode 2).
(See DTC TABLE [L8, LF].)
5
VERIFY CURRENT INPUT SIGNAL STATUS
•  Perform the PID/DATA Monitor and Record Procedure and access the following PIDs:
―  APP1
―  APP2
―  ECT
―  MAF
―  TP REL
―  VSS
•  Is there any signal that is far out of specification when the ignition switch is at the ON position and the engine runs?
Yes
Inspect the sensor and excessive resistance in related wiring harnesses.
Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.
No
Go to the next step.
6
VERIFY CURRENT INPUT SIGNAL STATUS UNDER FREEZE FRAME DATA (MODE 2) CONDITION
•  Perform the PID/DATA Monitor and Record Procedure and access the same PIDs as Step 5 under the FREEZE FRAME DATA (Mode 2) condition.
•  Is there any signal which causes drastic changes?
Yes
Inspect the sensor and excessive resistance in related wiring harnesses.
Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.
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 22.
(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 22.
10
INSPECT GAS LEAKAGE FROM EXHAUST SYSTEM
•  Visually inspect if there is any gas leakage is found between the exhaust manifold and A/F sensor.
•  Is there gas leakage?
Yes
Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.
(See EXHAUST SYSTEM REMOVAL/INSTALLATION [L8, LF].)
No
Replace the A/F sensor, then go to Step 22.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [L8, LF].)
11
VERIFY CURRENT INPUT SIGNAL STATUS OF MAF SENSOR
•  Connect the M-MDS to the DLC-2.
•  Start the engine.
•  Perform the PID/DATA Monitor and Record Procedure and access the MAF PID.
•  Verify that the MAF PID changes quickly according to engine speed.
•  Is the PID normal?
Yes
Go to the next step.
No
Replace the MAF/IAT sensor, then go to Step 22.
(See MASS AIR FLOW (MAF)/INTAKE AIR TEMPERATURE (IAT) SENSOR REMOVAL/INSTALLATION [L8, LF].)
12
INSPECT PURGE SOLENOID OPERATION
•  Perform 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 22.
13
INSPECT EGR VALVE OPERATION
•  Perform the EGR Control System Inspection.
•  Does the EGR 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 22.
14
INSPECT VARIABLE TUMBLE CONTROL OPERATION
•  Perform the Variable Tumble Control Operation Inspection.
•  Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.
No
Go to the next step.
15
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 Step 22.
No
Go to the next step.
16
INSPECT FUEL LINE PRESSURE
•  Turn the ignition switch off.
•  Inspect the fuel line pressure.
•  Is the fuel line pressure normal?
Yes
Go to Step 18.
No
If the fuel pressure is too high:
•  Replace the fuel pump unit, then go to Step 22.
If the fuel line pressure is low:
•  Go to the next step.
17
INSPECT FUEL SYSTEM FOR FUEL LEAKAGE
•  Visually inspect the fuel line for any leakage.
•  Is there fuel leakage?
Yes
Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.
No
Inspect the fuel filters for the foreign material or stain inside the fuel filter (low-pressure side).
If foreign material or stain is found inside the fuel filter (low-pressure side):
•  Clean the fuel tank and fuel filter.
If normal:
•  Replace the fuel pump unit.
Go to Step 22.
18
INSPECT IGNITION COIL AND RELATED WIRING HARNESS
•  Inspect the ignition coil and related wiring harness.
•  Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.
No
Go to the next step.
19
INSPECT IGNITION SYSTEM
•  Perform 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 22.
20
INSPECT VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION
•  Perform the Variable Valve Timing Control System Operation Inspection.
•  Does the 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 22.
21
INSPECT PCV VALVE OPERATION
•  Inspect the PCV valve operation.
•  Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results, then go to the next step.
No
Go to the next step.
22
VERIFY DTC TROUBLESHOOTING COMPLETED
•  Make sure to reconnect all disconnected connectors.
•  Clear the DTC from the PCM memory using the M-MDS.
•  Perform the KOER self test.
•  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.
23
VERIFY AFTER REPAIR PROCEDURE
•  Perform the “AFTER REPAIR PROCEDURE”.
•  Are any DTCs present?
Yes
Go to the applicable DTC troubleshooting.
(See DTC TABLE [L8, LF].)
No
DTC troubleshooting completed.