DTC P2178


DTC P2178	System too rich off idle
DETECTION CONDITION	• The PCM monitors short term fuel trim (SHRTFT) and 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 the 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 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. • The PENDING CODE is available if the PCM detects the above malfunction conditions during the first drive cycle. • The FREEZE FRAME DATA is available. • The DTC is stored in the PCM memory.
POSSIBLE CAUSE	• Misfire • HO2S deterioration • HO2S heater malfunction • MAF sensor malfunction • Pressure regulator (built-in fuel pump unit) malfunction • Fuel pump malfunction • EGR valve improper operation • Variable tumble shutter valve actuator improper operation • Purge solenoid valve improper operation • Purge solenoid valve malfunction (stuck open) • Purge solenoid hoses improper connection • Variable valve timing control system improper operation • PCV valve malfunction • PCM malfunction


STEP	INSPECTION		ACTION
1	PERFORM DTC CONFIRMATION PROCEDURE • Perform the DTC CONFIRMATION PROCEDURE. • Is the same DTC present?	Yes	Go to the next step.
1		No	Intermittent concern exists. Go to the INTERMITTENT CONCERN TROUBLESHOOTING procedures.
2	VERIFY RELATED PENDING CODE OR STORED DTC • Turn the ignition switch off, then to the ON position (Engine off). • Verify the related PENDING CODE or stored DTCs. • Are other DTCs present?	Yes	• If a misfire DTC is present, go to Step 7. • If are other DTC is present, go to the appropriate DTC inspection. (See DTC table (With WU-TWC).)
2		No	• If a driveability concern is present, go to Step 7. • If other, go to the next step.
3	IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA • Is DTC P2178 displayed in FREEZE FRAME DATA?	Yes	Go to the next step.
3		No	Go to the FREEZE FRAME DATA DTC inspection. (See DTC table (With WU-TWC).)
4	VERIFY CURRENT INPUT SIGNAL STATUS (IGNITION SWITCH TO ON/IDLE) • Access the ECT, MAF, TP, and VSS PIDs using the WDS or equivalent. • Is there any signal that is far out of specification during KOER?	Yes	Inspect the suspected sensor for excessive resistance in related the wiring harnesses. Repair or replace if necessary. Then go to Step 15.
4		No	Go to the next step.
5	VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION • Inspect the same PIDs as Step 3 while simulating the FREEZE FRAME DATA condition. • Is there any signal which causes drastic changes?	Yes	Inspect the suspected sensor and related wiring harnesses repair or replace it. Then go to Step 15.
5		No	Go to the next step.
6	VERIFY CURRENT INPUT SIGNAL STATUS OF HO2S • Access the O2S11 PID using the WDS or equivalent. • Verify the PID under the following accelerator pedal conditions (in PARK (ATX) or NEUTRAL (MTX)). • Is the PID normal? - Above 0.45 V when the accelerator pedal is suddenly depressed (rich condition) - Below 0.45 V just after releasing accelerator pedal (lean condition)	Yes	Go to the next step.
6		No	Visually the inspect for any gas leakage between exhaust manifold and HO2S. Then go to Step 15.
7	INSPECT MAF PID • Start engine. • Access the MAF PID using the WDS or equivalent. • Verify that the MAF PID changes quickly according to RPM when racing the engine. • Is the MAF PID response normal?	Yes	Go to the next step.
7		No	Replace the MAF/IAT sensor, then go to Step 15.
8	INSPECT PURGE SOLENOID OPERATION • Perform the "Purge Control System Inspection". • Does the purge control system work properly?	Yes	Go to the next step.
8		No	Repair or replace the malfunctioning part according to the inspection results, then go to Step 15.
9	INSPECT PCV VALVE OPERATION • Inspect the PCV valve operation. • Is the PCV valve normal?	Yes	Go to the next step.
9		No	Replace the PCV valve, then go to Step 15.
10	INSPECT EGR VALVE OPERATION • Perform the "EGR Control System Inspection". • Does the EGR control system work properly?	Yes	Go to the next step.
10		No	Repair or replace the malfunctioning parts according to the inspection results, then go to Step 15.
11	INSPECT VARIABLE TUMBLE SHUTTER VALVE ACTUATOR OPERATION • Perform the "Variable Tumble Control Operation Inspection". • Does the variable tumble control work properly?	Yes	Go to the next step.
11		No	Repair or replace the malfunctioning part according to inspection results, then go to Step 15.
12	INSPECT FUEL LINE PRESSURE • Turn the ignition switch off. Note • If the engine will not start, inspect the fuel line pressure with the ignition switch in the ON position. • Inspect the fuel line pressure while the engine is running. • Is the fuel line pressure normal?	Yes	Go to the next step.
12		No	If the fuel pressure is too high, replace the fuel pump unit, then go to Step 15. If the fuel line pressure is low, go to the next step.
13	INSPECT FUEL LINE FROM FUEL PUMP TO FUEL DELIVERY PIPE • Visually inspect the fuel line for leakage. • Is any fuel leakage found?	Yes	Replace the suspected fuel line, then go to Step 15.
13		No	Inspect the inside fuel filter (low pressure) for foreign material or stains. • If there is foreign material or stains are inside the fuel filter (low pressure), clean the fuel tank and the filter, then go to Step 15. • If there is not foreign material or stains are inside the fuel filter (low pressure), go to the next step.
14	INSPECT VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION • Inspect the variable valve timing control system operation. • Does the variable valve timing control system work properly?	Yes	Go to the next step.
14		No	Repair or replace the malfunctioning parts according to inspection results, then go to the next step.
15	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. • Is the same DTC present?	Yes	Replace the PCM, then go to the next step.
15		No	Go to the next step.
16	VERIFY AFTER REPAIR PROCEDURE • Perform the "AFTER REPAIR PROCEDURE". • Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC table (With WU-TWC).)
16		No	DTC troubleshooting completed.