DTC P2178

DETECTION CONDITION AND POSSIBLE CAUSE (DTC P2178 - LF, L3)

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. 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 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 PCM detects the above malfunction conditions during first drive cycle. FREEZE FRAME DATA is available. DTC is stored in the PCM memory.
POSSIBLE CAUSE	Misfire Front HO2S deterioration Front HO2S heater malfunction MAF sensor malfunction Pressure regulator (built-in fuel injection pump) malfunction Fuel pump malfunction EGR valve improper operation Variable tumble solenoid valve improper operation Purge solenoid valve improper operation Purge solenoid valve malfunction (stuck open) Purge solenoid hoses improper connection PCV valve malfunction Variable valve timing control system improper operation PCM malfunction

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. 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 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 PCM detects the above malfunction conditions during first drive cycle.
FREEZE FRAME DATA is available.
DTC is stored in the PCM memory.

POSSIBLE CAUSE

Misfire
Front HO2S deterioration
Front HO2S heater malfunction
MAF sensor malfunction
Pressure regulator (built-in fuel injection pump) malfunction
Fuel pump malfunction
EGR valve improper operation
Variable tumble solenoid valve improper operation
Purge solenoid valve improper operation
Purge solenoid valve malfunction (stuck open)
Purge solenoid hoses improper connection
PCV valve malfunction
Variable valve timing control system improper operation
PCM malfunction

DIAGNOSTIC PROCEDURE CHART

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED Diagnostic procedure Have FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (Fuel system related) been recorded?	Yes	Go to the next step.
1		No	Record the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.
2	VERIFY RELATED REPAIR INFORMATION AVAILABILITY Verify related Service Bulletins and/or on-line repair information availability. Is any related repair information available?	Yes	Perform repair or diagnosis according to the available repair information. If the vehicle is not repaired, go to the next step.
2		No	Go to the next step.
3	VERIFY RELATED PENDING CODE OR STORED DTCS Turn the ignition switch off, then to the ON position (Engine off). Verify related pending code or stored DTCs. Is other DTC present?	Yes	If misfire DTC is present, go to Step 8. If other DTC is present, go to applicable DTC inspection. (See DTC TABLE ).
3		No	If driveability concern is present, go to Step 8. If not, go to the next step.
4	IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA Is DTC P2178 on FREEZE FRAME DATA?	Yes	Go to the next step.
4		No	Go to troubleshooting procedures for DTC on FREEZE FRAME DATA.
5	VERIFY CURRENT INPUT SIGNAL STATUS (IGNITION SWITCH TO THE ON POSITION/IDLE) Access APP1, APP2, ECT, MAF, TP1 and VSS PIDs using WDS or equivalent. 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 if necessary. Then go to Step 16.
5		No	Go to the next step.
6	VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION Inspect the same PIDs as Step 5 while simulating FREEZE FRAME DATA condition. Is there any signal which causes drastic changes?	Yes	Inspect the sensor and related wiring harnesses, repair or replace it. Then go to Step 16.
6		No	Go to the next step.
7	VERIFY CURRENT INPUT SIGNAL STATUS OF FRONT HO2S Access O2S11 for P2177 PID using WDS or equivalent. Check PID under following accelerator pedal condition (in PARK (ATX) or NEUTRAL (MTX). Is PID reading normal? Less than 1 mA when accelerator pedal is suddenly depressed (rich condition). More than 1 mA just after release of accelerator pedal (lean condition)	Yes	Go to the next step.
7		No	Visually inspect for any gas leakage between the exhaust manifold and the front HO2S. Then go to Step 16.
8	VERIFY CURRENT INPUT SIGNAL STATUS OF MAF SENSOR Connect the WDS or equivalent to the DLC-2 Start the engine. 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.
8		No	Replace the MAF/IAT sensor, then go to Step 16.
9	INSPECT PURGE SOLENOID OPERATION Perform Purge Control System Inspection. (See PURGE CONTROL SYSTEM INSPECTION ). Does purge control system work properly?	Yes	Go to the next step.
9		No	Repair or replace the malfunctioning part according to inspection result, then go to Step 16.
10	INSPECT PCV VALVE OPERATION Inspect the PCV valve operation. (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION ). Is the PCV valve normal?	Yes	Go to the next step.
10		No	Replace the PCV valve, then go to Step 16.
11	INSPECT EGR VALVE OPERATION Perform EGR Control System Inspection. (See EGR CONTROL SYSTEM INSPECTION ). Does the EGR control system work properly?	Yes	Go to the next step.
11		No	Repair or replace the malfunctioning part according to inspection result, then go to Step 16.
12	INSPECT VTCS OPERATION Perform Variable Tumble Control Operation Inspection. (See VARIABLE TUMBLE CONTROL OPERATION INSPECTION ). Does the VTCS work properly?	Yes	Go to Step 15.
12		No	Repair or replace the malfunctioning part according to inspection result, then go to Step 16.
13	INSPECT FUEL LINE PRESSURE Turn the ignition switch off. Inspect the fuel line pressure. (See FUEL LINE PRESSURE INSPECTION ). Is the fuel line pressure normal?	Yes	Go to the next step.
13		No	If the fuel pressure is too high, replace fuel pump unit, then go to Step 16. If the fuel line pressure is low, go to the next step.
14	INSPECT FUEL LINE FROM FUEL PUMP TO FUEL DELIVERY PIPE Visually inspect the fuel line for any leakage. Is fuel leakage found?	Yes	Replace suspected fuel line, then go to the next step.
14		No	Inspect for foreign materials or stain inside fuel filter (low-pressure). If for foreign materials or stain inside fuel filter (low-pressure), clean off the fuel tank and filter. Then go to the next step.
15	INSPECT VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION Inspect variable valve timing control system operation. (See VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION INSPECTION ). Does variable valve timing control system work properly?	Yes	Go to the next step.
15		No	Repair or replace the malfunctioning part according to inspection results, then go to the next step.
16	VERIFY TROUBLESHOOTING OF DTC P2178 COMPLETED Make sure to reconnect all disconnected connectors. Clear the DTC from the PCM memory using the WDS or equivalent. Perform the KOER self-test or the PCM Adaptive Memory Produce Drive Mode. (See OBD-II DRIVE MODE ). Is the PENDING CODE for this DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION ).
16		No	Go to the next step.
17	VERIFY AFTER REPAIR PROCEDURE Perform "AFTER REPAIR PROCEDURE". (See AFTER REPAIR PROCEDURE ). Is there any DTC present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE ).
17		No	Troubleshooting completed.