Diagnostic procedure

DTC P0171 DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED Have FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (Fuel system related) been recorded?	Yes	Go to the next step.
1		No	Record FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on repair order, then go to the next step.
2	VERIFY RELATED REPAIR INFORMATION AVAILABILITY Check for related Technical Service Bulletin(s) repair information availability. Is any related repair information available?	Yes	Perform repair or diagnosis according to available repair information. If 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 DTCs present?	Yes	If misfire DTC is present, go to Step 8. If other DTC is present, go to appropriate DTC troubleshooting procedures. (See DTC TABLE )
3		No	If drive ability concern is present, go to Step 8. If not, go to the next step.
4	IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA Is DTC P0171 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 KEY TO ON/IDLE) Access APP1, APP2, ECT, MAF, TP and VSS PIDs using WDS or equivalent. (See PCM INSPECTION .) Is there any signal that is far out of specification when ignition switch is ON and engine runs?	Yes	Inspect suspected sensor and excessive resistance in related wiring harnesses. Repair or replace if necessary. Then go to Step 16.
5		No	Go to the next step.
6	VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION Inspect same PIDs as Step 5 while simulating FREEZE FRAME DATA condition. Is there any input signal which causes drastic changes?	Yes	Inspect suspected sensor and related wiring harnesses, and 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 P0171 PID using WDS or equivalent. Check PID under following accelerator pedal condition (in PARK (ATX) or NEUTRAL (MTX)). Is PID reading normal? Except for California emission regulation applicable model Above 0.55 V when accelerator pedal is suddenly depressed (rich condition). Below 0.55 V just after release of accelerator pedal (lean condition) California emission regulation applicable model Less than 1 mA when accelerator pedal is suddenly depress (rich condition) More than 1 mA just after release of accelerator pedal (lean condition)	Yes	Inspect for air suction at followings due to cracks, damages and loosening parts: From air cleaner to throttle body From throttle body to dynamic chamber From dynamic chamber to intake manifold Vacuum hoses NOTE: Engine speed may change when rust penetrating agent is sprayed on the air suction area. Repair or replace any faulty part, then go to Step 16.
7		No	Visually inspect for any gas leakage between exhaust manifold and front HO2S. If there is no leakage, replace FRONT HO2S. Then go to Step 16.
8	INSPECT MAF PID Start engine. Access MAF PID using WDS or equivalent. Verify that MAF PID changes quickly according to race engine RPM. Is MAF PID response normal?	Yes	Go to the next step.
8		No	Replace Mass air flow sensor, then go to Step 16.
9	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 source of air suction, then go to Step 16.
9		No	Go to the next step.
10	INSPECT FUEL LINE PRESSURE Turn the ignition switch off. NOTE: If engine won't start, inspect fuel line pressure with ignition switch ON. Inspect fuel line pressure while engine running. (See FUEL LINE PRESSURE INSPECTION .) Is fuel line pressure normal?	Yes	Go to Step 12.
10		No	If fuel line pressure is too high: Replace fuel pump unit, then go to Step 16. If fuel line pressure is too low: Go to the next step.
11	INSPECT FUEL LINE FROM FUEL PUMP TO FUEL DELIVERY PIPE Visually inspect fuel line for any leakage. Is fuel leakage found?	Yes	Replace suspected fuel line, then go to Step 16.
11		No	Inspect low-pressure side fuel filter for follows: Foreign materials or stain inside fuel filter Perform following actions as result. If foreign materials or stain is found inside fuel filter (low-pressure side), clean of fuel tank and filter. If normal, replace fuel pump unit. Then go to Step 16.
12	INSPECT IGNITION COIL HARNESSES Inspect the ignition coil related harness condition (intermittent open or short) for all cylinders. Are harness conditions normal?	Yes	Go to the next step.
12		No	Repair suspected wiring harnesses, then go to Step 16.
13	INSPECT IGNITION SYSTEM OPERATION Carry out spark test. (See SPARK TEST ) Is strong blue spark visible at each cylinder?	Yes	Go to the next step.
13		No	Repair or replace malfunctioning part according to spark test result. Then go to Step 16.
14	INSPECT ENGINE COMPRESSION Inspect engine compression. (See COMPRESSION INSPECTION .) Is it normal?	Yes	Go to the next step.
14		No	Implement engine overhaul for repairs, then go to Step 19.
15	INSPECT FUEL INJECTOR OPERATION Remove fuel injector. Inspect injector operation. Is fuel injector normal?	Yes	Go to the next step.
15		No	Replace injector, then go to the next step.
16	VERIFY TROUBLESHOOTING OF DTC P0171 COMPLETED Make sure to reconnect all disconnected connectors. Clear DTC from PCM memory using WDS or equivalent. Perform the "PCM Adaptive Memory Produce Drive Mode" and "HO2S heater, HO2S, and TWC Repair Verification Drive Mode". (See OBD-II DRIVE MODE ) Stop vehicle and access ON BOARD READINESS TEST to inspect DRIVE MODE completion status. Verify FUEL_EVAL PID changes to yes. If not, perform the "HO2S heater, HO2S, and TWC Repair Verification Drive Mode" again. Access PENDING CODE. Is the PENDING CODE for this DTC present?	Yes	Replace 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 applicable DTC inspection. (See DTC TABLE )
17		No	Troubleshooting completed.