DTC P2177 [L8, LF]

DTC P2177	Fuel system too lean 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 lean 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 • Air suction in intake air system • Purge system malfunction ― Purge solenoid valve improper operation ― Improper connection purge solenoid hose ― Purge solenoid valve malfunction (stuck open) • Improper operation of fuel injector • Fuel supply system malfunction or improper fuel line malfunction ― Pressure regulator (built-in fuel pump unit) malfunction ― Clogged or restricted fuel filter (built-in fuel pump unit) ― 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 • Insufficient compression • Misfire • PCM malfunction

DTC P2177

Fuel system too lean 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 lean 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

• Air suction in intake air system

• Purge system malfunction

― Purge solenoid valve improper operation

― Improper connection purge solenoid hose

― Purge solenoid valve malfunction (stuck open)

• Improper operation of fuel injector

• Fuel supply system malfunction or improper fuel line malfunction

― Pressure regulator (built-in fuel pump unit) malfunction

― Clogged or restricted fuel filter (built-in fuel pump unit)

― 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

• Insufficient compression

• Misfire

• PCM malfunction

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. (See ON-BOARD DIAGNOSTIC TEST [L8, LF].) • 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. (See DTC TABLE [L8, LF].)
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. (See ON-BOARD DIAGNOSTIC TEST [L8, LF].) • Is the DTC P2177 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: (See ON-BOARD DIAGNOSTIC TEST [L8, LF].) ― 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? (See PCM INSPECTION [L8, LF].)	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 21.
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. (See ON-BOARD DIAGNOSTIC TEST [L8, LF].) • 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 21.
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 [L8, LF].) • 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. (See AIR FUEL RATIO (A/F) SENSOR INSPECTION [L8, LF].) • 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.
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 21. (See EXHAUST SYSTEM REMOVAL/INSTALLATION [L8, LF].)
No	Replace the A/F sensor, then go to Step 21. (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. (See ON-BOARD DIAGNOSTIC TEST [L8, LF].) • Verify that the MAF PID changes quickly according to engine speed. • Is the PID normal? (See PCM INSPECTION [L8, LF].)	Yes	Go to Step 13.
No	Go to the next step.
12	INSPECT FOR EXCESSIVE AIR SUCTION OF INTAKE AIR SYSTEM • Visually inspect for loosen, cracks or damages hoses on intake air system. • Is there any malfunction?	Yes	Repair or replace the malfunctioning part according to the inspection results, then go to Step 21.
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].)
13	INSPECT PURGE SOLENOID OPERATION • Perform the Purge Control System Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].) • 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.
14	INSPECT FUEL INJECTOR OPERATION • Perform the Fuel Injector Operation Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].) • Is there any malfunction?	Yes	Repair or replace the malfunctioning part according to the inspection results, then go to Step 21.
No	Go to the next step.
15	INSPECT FUEL LINE PRESSURE • Turn the ignition switch off. • Inspect the fuel line pressure. (See FUEL LINE PRESSURE INSPECTION [L8, LF].) • Is the fuel line pressure normal?	Yes	Go to Step 17.
No	If the fuel pressure is too high: • Replace the fuel pump unit, then go to Step 21. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF].) If the fuel line pressure is low: • Go to the next step.
16	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 21.
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. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF].) Go to Step 21.
17	INSPECT IGNITION COIL 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 21.
No	Go to the next step.
18	INSPECT IGNITION SYSTEM • Perform the Spark Test. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].) • 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 VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION • Perform the Variable Valve Timing Control System Operation Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].) • 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 21.
20	INSPECT ENGINE COMPRESSION • Inspect the engine compression. (See COMPRESSION INSPECTION [L8, LF].) • Is there any malfunction?	Yes	Perform the engine overhaul for repairs, then go to the next step.
No	Go to the next step.
21	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 [L8, LF].) • Perform the KOER self test. (See KOEO/KOER SELF TEST [L8, LF].) • 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”. (See AFTER REPAIR PROCEDURE [L8, LF].) • Are any DTCs present?	Yes	Go to the applicable DTC troubleshooting. (See DTC TABLE [L8, LF].)
No	DTC troubleshooting completed.

STEP

INSPECTION

ACTION

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.

Record the FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS on 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 to the ON position (engine off).

• Perform the Pending Trouble Code Access Procedure and DTC Reading Procedure.

(See ON-BOARD DIAGNOSTIC TEST [L8, LF].)

• 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.

(See DTC TABLE [L8, LF].)

If driveability concern is present:

• Go to Step 11.

If not:

• Go to the next step.

IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA (MODE 2)

• Perform the Freeze Frame PID Data Access Procedure.

(See ON-BOARD DIAGNOSTIC TEST [L8, LF].)

• Is the DTC P2177 on FREEZE FRAME DATA (Mode 2)?

Yes

Go to the next step.

Go to the DTC troubleshooting on FREEZE FRAME DATA (Mode 2).

(See DTC TABLE [L8, LF].)

VERIFY CURRENT INPUT SIGNAL STATUS

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

(See ON-BOARD DIAGNOSTIC TEST [L8, LF].)

― 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?

(See PCM INSPECTION [L8, LF].)

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 21.

Go to the next step.

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.

(See ON-BOARD DIAGNOSTIC TEST [L8, LF].)

• 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 21.

Go to the next step.

INSPECT A/F SENSOR HEATER

• Inspect the A/F sensor heater.

(See AIR FUEL RATIO (A/F) SENSOR INSPECTION [L8, LF].)

• 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].)

Go to the next step.

INSPECT A/F SENSOR

• Inspect the A/F sensor.

(See AIR FUEL RATIO (A/F) SENSOR INSPECTION [L8, LF].)

• 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 21.

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 21.

(See EXHAUST SYSTEM REMOVAL/INSTALLATION [L8, LF].)

Replace the A/F sensor, then go to Step 21.

(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [L8, LF].)

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 [L8, LF].)

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

• Is the PID normal?

(See PCM INSPECTION [L8, LF].)

Yes

Go to Step 13.

Go to the next step.

INSPECT FOR EXCESSIVE AIR SUCTION OF INTAKE AIR SYSTEM

• Visually inspect for loosen, cracks or damages hoses on intake air system.

• Is there any malfunction?

Yes

Repair or replace the malfunctioning part according to the inspection results, then go to Step 21.

Replace the MAF/IAT sensor, then go to Step 21.

(See MASS AIR FLOW (MAF)/INTAKE AIR TEMPERATURE (IAT) SENSOR REMOVAL/INSTALLATION [L8, LF].)

INSPECT PURGE SOLENOID OPERATION

• Perform the Purge Control System Inspection.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].)

• Does the purge 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 21.

INSPECT FUEL INJECTOR OPERATION

• Perform the Fuel Injector Operation Inspection.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].)

• Is there any malfunction?

Yes

Repair or replace the malfunctioning part according to the inspection results, then go to Step 21.

Go to the next step.

INSPECT FUEL LINE PRESSURE

• Turn the ignition switch off.

• Inspect the fuel line pressure.

(See FUEL LINE PRESSURE INSPECTION [L8, LF].)

• Is the fuel line pressure normal?

Yes

Go to Step 17.

If the fuel pressure is too high:

• Replace the fuel pump unit, then go to Step 21.

(See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF].)

If the fuel line pressure is low:

• Go to the next step.

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 21.

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.

(See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF].)

Go to Step 21.

INSPECT IGNITION COIL 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 21.

Go to the next step.

INSPECT IGNITION SYSTEM

• Perform the Spark Test.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].)

• 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 21.

INSPECT VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION

• Perform the Variable Valve Timing Control System Operation Inspection.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].)

• 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 21.

INSPECT ENGINE COMPRESSION

• Inspect the engine compression.

(See COMPRESSION INSPECTION [L8, LF].)

• Is there any malfunction?

Yes

Perform the engine overhaul for repairs, then go to the next step.

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 [L8, LF].)

• Perform the KOER self test.

(See KOEO/KOER SELF TEST [L8, LF].)

• Is the PENDING CODE for this DTC present?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION [L8, LF].)

Go to the next step.

VERIFY AFTER REPAIR PROCEDURE

• Perform the “AFTER REPAIR PROCEDURE”.

(See AFTER REPAIR PROCEDURE [L8, LF].)

• Are any DTCs present?

Yes

Go to the applicable DTC troubleshooting.

(See DTC TABLE [L8, LF].)

DTC troubleshooting completed.