DTC P2178:00 [ZJ, ZY]

DTC P2178:00	Fuel system too rich at 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 or the sum total of these fuel trims exceed pre programmed 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 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. • 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 gas ― A/F sensor malfunction • MAF sensor malfunction • Improper operation of purge solenoid valve • Improper operation of EGR valve • Improper operation of variable tumble shutter valve actuator • Improper operation of fuel injector • Improper operation of variable valve timing control system • Fuel supply system 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 unit • Ignition system malfunction ― Ignition coil and related wiring harness malfunction ― Spark plug malfunction • Improper operation of PCV valve • PCM malfunction

DTC P2178:00

Fuel system too rich at 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 or the sum total of these fuel trims exceed pre programmed 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 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.

• 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 gas

― A/F sensor malfunction

• MAF sensor malfunction

• Improper operation of purge solenoid valve

• Improper operation of EGR valve

• Improper operation of variable tumble shutter valve actuator

• Improper operation of fuel injector

• Improper operation of variable valve timing control system

• Fuel supply system 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 unit

• Ignition system malfunction

― Ignition coil and related wiring harness malfunction

― Spark plug malfunction

• Improper operation of PCV valve

• PCM malfunction

STEP	INSPECTION	ACTION
1	VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED • Have the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (fuel system related) been recorded?	Yes	Go to the next step.
No	Record the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on the 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 ON position (engine off). • Verify the related PENDING CODE and stored DTCs using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [ZJ, ZY].) • Are any other DTC present?	Yes	If the misfire DTC is present: • Go to Step 11. If other DTC is present: • Go to the applicable DTC inspection. (See DTC TABLE [ZJ, ZY].)
No	If drive ability concern is present: • Go to Step 11. If other: • Go to the next step.
4	IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA • Is the DTC P2178:00 on FREEZE FRAME DATA?	Yes	Go to the next step.
No	Go to the troubleshooting procedures for DTC on FREEZE FRAME DATA. (See DTC TABLE [ZJ, ZY].)
5	VERIFY CURRENT INPUT SIGNAL STATUS • Connect the M-MDS to the DLC-2. • Perform the PID/DATA Monitor and Record Procedure and access the following PIDs: (See ON-BOARD DIAGNOSTIC TEST [ZJ, ZY].) ― APP ― ECT ― MAF ― TP REL ― VSS • Is there any signal that is far out of specification when KOER? (See PCM INSPECTION [ZJ, ZY].)	Yes	Inspect the suspected sensor and related wiring harness. 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 CONDITION • Perform the PID/DATA Monitor and Record Procedure and access the same PIDs as in Step 5 under the FREEZE FRAME DATA condition. (See ON-BOARD DIAGNOSTIC TEST [ZJ, ZY].) • 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 22.
No	Go to the next step.
7	INSPECT A/F SENSOR HEATER • Inspect the A/F sensor heater. (See AIR FUEL RATIO (A/F) SENSOR INSPECTION [ZJ, ZY].) • Is there any malfunction?	Yes	Replace the A/F sensor, then go to Step 22. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [ZJ, ZY].)
No	Go to the next step.
8	INSPECT A/F SENSOR • Inspect the A/F sensor. (See AIR FUEL RATIO (A/F) SENSOR INSPECTION [ZJ, ZY].) • 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. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [ZJ, ZY].)
10	INSPECT GAS LEAKAGE FROM EXHAUST SYSTEM • Visually inspect if there is exhaust gas leakage 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.
No	Replace the A/F sensor, then go to Step 22. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [ZJ, ZY].)
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. (See ON-BOARD DIAGNOSTIC TEST [ZJ, ZY].) • Verify that the MAF PID changes quickly according to race the 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 [ZJ, ZY].)
12	INSPECT PURGE SOLENOID VALVE OPERATION • Perform the Purge Control System Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY].) • Does the purge control system function 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. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY].) • Does the variable tumble control 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 SHUTTER VALVE ACTUATOR OPERATION • Perform the Variable Tumble Control Operation Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY].) • 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.
15	INSPECT FUEL INJECTOR OPERATION • Perform the Fuel Injector Operation Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY].) • Does the fuel injector 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.
16	INSPECT VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION • Perform the Variable Valve Timing Control System Operation Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY].) • 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.
17	INSPECT FUEL LINE PRESSURE • Turn the ignition switch off. Note • If the engine will not start, inspect the fuel line pressure with ignition switch to the ON position. • Perform the ”FUEL LINE PRESSURE INSPECTION” while the engine running. (See FUEL LINE PRESSURE INSPECTION [ZJ, ZY].) • Is the fuel line pressure normal?	Yes	Go to Step 19.
No	If the fuel pressure is too high: • Replace the fuel pump unit, then go to Step 22. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [ZJ, ZY].) If the fuel pressure is low: • Go to the next step.
18	INSPECT FUEL SYSTEM FOR FUEL LEAKAGE • Visually inspect the fuel leakage in the fuel system. • Is there fuel leakage?	Yes	Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.
No	Inspect for foreign materials or stain inside fuel filter (low pressure). • If for foreign materials or stain inside fuel filter (low pressure): ― Clean the fuel tank and filter, then go to Step 22.
19	INSPECT IGNITION COIL AND RELATED WIRING HARNESS • Inspect the ignition coil and related wiring harness condition (intermittent open or short circuit) for all cylinders. (See IGNITION COIL INSPECTION [ZJ, ZY].) • Is there any malfunction?	Yes	Repair or replace the malfunctioning part according to the inspection results, then go to Step 22. (See IGNITION COIL REMOVAL/INSTALLATION [ZJ, ZY].)
No	Go to the next step.
20	INSPECT IGNITION SYSTEM OPERATION • Perform the Spark Test. (See.ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY]) • 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.
21	INSPECT PCV VALVE OPERATION • Inspect the PCV valve operation. (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [ZJ, ZY].) • Is there any malfunction?	Yes	Replace the PCV valve and the oil separator as a single unit, then go to the next step. (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION [ZJ, ZY].)
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. (See AFTER REPAIR PROCEDURE [ZJ, ZY].) • Perform the KOER self test. (See KOEO/KOER SELF TEST [ZJ, ZY].) • Is the PENDING CODE for this DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [ZJ, ZY].)
No	Go to the next step.
23	VERIFY AFTER REPAIR PROCEDURE • Perform the “AFTER REPAIR PROCEDURE”. (See AFTER REPAIR PROCEDURE [ZJ, ZY].) • Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [ZJ, ZY].)
No	DTC troubleshooting completed.

STEP

INSPECTION

ACTION

VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED

• Have the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (fuel system related) been recorded?

Yes

Go to the next step.

Record the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.

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.

Go to the next step.

VERIFY RELATED PENDING CODE AND STORED DTC

• Turn the ignition switch off, then ON position (engine off).

• Verify the related PENDING CODE and stored DTCs using the M-MDS.

(See ON-BOARD DIAGNOSTIC TEST [ZJ, ZY].)

• Are any other DTC present?

Yes

If the misfire DTC is present:

• Go to Step 11.

If other DTC is present:

• Go to the applicable DTC inspection.

(See DTC TABLE [ZJ, ZY].)

If drive ability concern is present:

• Go to Step 11.

If other:

• Go to the next step.

IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA

• Is the DTC P2178:00 on FREEZE FRAME DATA?

Yes

Go to the next step.

Go to the troubleshooting procedures for DTC on FREEZE FRAME DATA.

(See DTC TABLE [ZJ, ZY].)

VERIFY CURRENT INPUT SIGNAL STATUS

• Connect the M-MDS to the DLC-2.

• Perform the PID/DATA Monitor and Record Procedure and access the following PIDs:

(See ON-BOARD DIAGNOSTIC TEST [ZJ, ZY].)

― APP

― ECT

― MAF

― TP REL

― VSS

• Is there any signal that is far out of specification when KOER?

(See PCM INSPECTION [ZJ, ZY].)

Yes

Inspect the suspected sensor and related wiring harness.

Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.

Go to the next step.

VERIFY CURRENT INPUT SIGNAL STATUS UNDER FREEZE FRAME DATA CONDITION

• Perform the PID/DATA Monitor and Record Procedure and access the same PIDs as in Step 5 under the FREEZE FRAME DATA condition.

(See ON-BOARD DIAGNOSTIC TEST [ZJ, ZY].)

• 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 22.

Go to the next step.

INSPECT A/F SENSOR HEATER

• Inspect the A/F sensor heater.

(See AIR FUEL RATIO (A/F) SENSOR INSPECTION [ZJ, ZY].)

• Is there any malfunction?

Yes

Replace the A/F sensor, then go to Step 22.

(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [ZJ, ZY].)

Go to the next step.

INSPECT A/F SENSOR

• Inspect the A/F sensor.

(See AIR FUEL RATIO (A/F) SENSOR INSPECTION [ZJ, ZY].)

• Is there any malfunction?

Yes

Go to the next step.

Go to Step 11.

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.

Retighten the A/F sensor, then go to Step 22.

(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [ZJ, ZY].)

INSPECT GAS LEAKAGE FROM EXHAUST SYSTEM

• Visually inspect if there is exhaust gas leakage 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.

Replace the A/F sensor, then go to Step 22.

(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [ZJ, ZY].)

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.

(See ON-BOARD DIAGNOSTIC TEST [ZJ, ZY].)

• Verify that the MAF PID changes quickly according to race the engine speed.

• Is the PID normal?

Yes

Go to the next step.

Replace the MAF/IAT sensor, then go to Step 22.

(See MASS AIR FLOW (MAF)/INTAKE AIR TEMPERATURE (IAT) SENSOR REMOVAL/INSTALLATION [ZJ, ZY].)

INSPECT PURGE SOLENOID VALVE OPERATION

• Perform the Purge Control System Inspection.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY].)

• Does the purge control system function properly?

Yes

Go to the next step.

Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.

INSPECT EGR VALVE OPERATION

• Perform the EGR Control System Inspection.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY].)

• Does the variable tumble control work properly?

Yes

Go to the next step.

Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.

INSPECT VARIABLE TUMBLE SHUTTER VALVE ACTUATOR OPERATION

• Perform the Variable Tumble Control Operation Inspection.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY].)

• Does the EGR control system work properly?

Yes

Go to the next step.

Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.

INSPECT FUEL INJECTOR OPERATION

• Perform the Fuel Injector Operation Inspection.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY].)

• Does the fuel injector work properly?

Yes

Go to the next step.

Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.

INSPECT VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION

• Perform the Variable Valve Timing Control System Operation Inspection.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY].)

• Does the variable valve timing control system work properly?

Yes

Go to the next step.

Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.

INSPECT FUEL LINE PRESSURE

• Turn the ignition switch off.

Note

• If the engine will not start, inspect the fuel line pressure with ignition switch to the ON position.

• Perform the ”FUEL LINE PRESSURE INSPECTION” while the engine running.

(See FUEL LINE PRESSURE INSPECTION [ZJ, ZY].)

• Is the fuel line pressure normal?

Yes

Go to Step 19.

If the fuel pressure is too high:

• Replace the fuel pump unit, then go to Step 22.

(See FUEL PUMP UNIT REMOVAL/INSTALLATION [ZJ, ZY].)

If the fuel pressure is low:

• Go to the next step.

INSPECT FUEL SYSTEM FOR FUEL LEAKAGE

• Visually inspect the fuel leakage in the fuel system.

• Is there fuel leakage?

Yes

Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.

Inspect for foreign materials or stain inside fuel filter (low pressure).

• If for foreign materials or stain inside fuel filter (low pressure):

― Clean the fuel tank and filter, then go to Step 22.

INSPECT IGNITION COIL AND RELATED WIRING HARNESS

• Inspect the ignition coil and related wiring harness condition (intermittent open or short circuit) for all cylinders.

(See IGNITION COIL INSPECTION [ZJ, ZY].)

• Is there any malfunction?

Yes

Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.

(See IGNITION COIL REMOVAL/INSTALLATION [ZJ, ZY].)

Go to the next step.

INSPECT IGNITION SYSTEM OPERATION

• Perform the Spark Test.

(See.ENGINE CONTROL SYSTEM OPERATION INSPECTION [ZJ, ZY])

• Is the strong blue spark visible at each cylinder?

Yes

Go to the next step.

Repair or replace the malfunctioning part according to the inspection results, then go to Step 22.

INSPECT PCV VALVE OPERATION

• Inspect the PCV valve operation.

(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [ZJ, ZY].)

• Is there any malfunction?

Yes

Replace the PCV valve and the oil separator as a single unit, then go to the next step.

(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION [ZJ, ZY].)

Go to the next step.

VERIFY DTC TROUBLESHOOTING COMPLETED

• Make sure to reconnect all disconnected connectors.

• Clear the DTC from the PCM memory using the M-MDS.

(See AFTER REPAIR PROCEDURE [ZJ, ZY].)

• Perform the KOER self test.

(See KOEO/KOER SELF TEST [ZJ, ZY].)

• Is the PENDING CODE for this DTC present?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION [ZJ, ZY].)

Go to the next step.

VERIFY AFTER REPAIR PROCEDURE

• Perform the “AFTER REPAIR PROCEDURE”.

(See AFTER REPAIR PROCEDURE [ZJ, ZY].)

• Are any DTCs present?

Yes

Go to the applicable DTC inspection.

(See DTC TABLE [ZJ, ZY].)

DTC troubleshooting completed.