Adaptive Fuel Control

DTC P0171, P0174 DETECTION CONDITION & POSSIBLE CAUSES

DTC P0171, P0174	ADAPTIVE FUEL CONTROL
DETECTION CONDITION	P0171 indicates the fuel/air ratio is too lean (RH). P0174 indicates the fuel/air ratio is too lean (LH).
POSSIBLE CAUSE	Fuel system: Low fuel pressure or running out of fuel Excessive fuel pressure Leaking fuel injector(s) Leaking fuel pressure regulator Vapor recovery system Contaminated fuel injector(s) Induction system: Air leaks after the mass air flow (MAF) Vacuum leaks (vacuum lines and gaskets) Restricted air inlet Positive crankcase ventilation (PCV) system Improperly seated engine oil dipstick Exhaust gas recirculation (EGR) system: Leaking gasket Stuck EGR valve Base engine: Oil overfill Cam timing Cylinder compression Exhaust leaks before or near the heated oxygen sensors (HO2S)
HINT	Fuel System Monitor The fuel control system uses fuel trim tables stored in the powertrain control module (PCM) to compensate for variability in fuel system components due to normal wear and aging. The fuel trim strategy learns deviations during closed-loop engine operation. The fuel trim has two means of adapting; a long term fuel trim and a short term fuel trim system. Inputs from engine coolant temperature (ECT), intake air temperature (IAT) and MAF sensors are required to activate the fuel trim system. The HO2S detects the presence of oxygen in the exhaust and provides the PCM with feedback indicating air/fuel ratio. A fuel trim factor is added to the fuel injector pulse width calculation according to the long and short term fuel trims. The long term trim values at their rich or lean limits indicate a fuel system malfunction.

DTC P0171, P0174 DIAGNOSTIC PROCEDURE

PTC P0171, P0174		ADAPTIVE FUEL CONTROL
STEP	INSPECTION		ACTION
1	Was the PCM quick test performed?	Yes	If misfire DTC (P0300-P0306) is present or drive ability concern is present, Go to step 6. If any other DTC is present, Go to appropriate DTC inspection. Otherwise, Go to next step.
1	Was the PCM quick test performed?	No	Perform PCM quick test.
2	IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA Is DTC P0171 or P0174 on freeze frame data?	Yes	Go to next step.
2		No	Go to troubleshooting procedure for DTCs on freeze frame data. See FREEZE FRAME CHARTS .
3	VERIFY CURRENT INPUT SIGNAL STATUS Key on, engine running (KOER). Access ECT V, MAF V, TP V and VSS PIDs using WDS or equivalent tester. Is there any signal that is far out of specification during KOER?	Yes	Inspect suspected sensor and excessive resistance in related wiring harnesses. Repair or replace if necessary. Go to step 14.
3		No	Go to next step.
4	VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION Access ECT V, MAF V, TP V and VSS PIDs while simulating freeze frame data condition. Is there any input signal which causes drastic changes?	Yes	Inspect suspected sensor and related wiring harnesses. Repair or replace if necessary. Go to step 14.
4		No	Go to next step.
5	VERIFY CURRENT INPUT SIGNAL STATUS OF FRONT HO2S (RH, LH) Access O2S11 PID for P0171 or O2S21 PIDforP0174. Check PID under following accelerator pedal condition (in PARK): sudden depress of accelerator pedal (rich condition) should read more than 0.45 V sudden release of accelerator pedal (lean condition) should read less than 0.45 V Is PID reading correctly?	Yes	Inspect for air suction at the following locations due to cracks, damage, and loose 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. Go to step 14.
5		No	Visually inspect for any gas leakage between exhaust manifold and HO2S. If there is no leakage, replace HO2S. See HEATED OXYGEN SENSOR (HO2S) REMOVAL / INSTALLATION . Go to step 14.
6	INSPECT MAF V PID Key on, engine running (KOER). Access MAF V PID using WDS or equivalent tester. Verify that MAF V PID changes quickly according to race engine RPM. Is MAF V PID response OK?	Yes	Go to next step.
6		No	Replace MAF sensor. See MASS AIR FLOW/INTAKE AIR TEMPERATURE (MAF/IAT) SENSOR REMOVAL / INSTALLATION . Go to step 14.
7	INSPECT FOR EXCESSIVE AIR SUCTION OF INTAKE AIR SYSTEM Visually inspect air intake system for cracks, damage, or loose parts. Is there a problem?	Yes	Repair or replace source of air suction. Go to step 14.
7		No	Go to next step.
8	INSPECT FUEL LINE PRESSURE. Key OFF. Connect fuel pressure gauge. Key on, engine running (KOER). Is fuel pressure within 207-448 kPa (30-65 psi)?	Yes	Go to step 12.
8		No	Go to next step.
9	INSPECT FUEL PUMP CIRCUIT Key OFF. Inspect fuel pump circuit for open or poor connection. Is circuit OK?	Yes	Go to next step.
9		No	Repair or replace suspected circuit. Go to step 14.
10	INSPECT FUEL LINE FROM FUEL PUMP TO FUEL DELIVERY LINE Visually inspect fuel line for any leakage. Is any fuel leakage found?	Yes	Replace fuel line. Go to step 14.
10		No	Go to next step.
11	INSPECT FUEL FILTER Inspect fuel filter for: Restriction or clogging at high pressure side Foreign material or stains at low pressure side Is anything found?	Yes	If anything is found at high pressure side, replace fuel filter. See FUEL FILTER REMOVAL / INSTALLATION . If anything is found at low pressure side, clean fuel tank and filter. See FUEL TANK REMOVAL / INSTALLATION . Go to step 14.
11		No	Replace fuel pump. See FUEL PUMP REMOVAL / INSTALLATION . Go to step 14.
12	INSPECT ENGINE COMPRESSION Perform an engine compression test. Is engine compression within correct specification?	Yes	Go to next step.
12		No	Overhaul engine.
13	INSPECT FUEL INJECTOR OPERATION Remove injector from suspected bank and swap with injector from other bank. Key on, engine running (KOER). Is fuel trim system lean for bank which has suspected injector?	Yes	Key OFF. Replace fuel injector. See FUEL INJECTION SUPPLY MANIFOLD AND FUEL INJECTOR - 2.3L REMOVAL / INSTALLATION FUEL INJECTION SUPPLY MANIFOLD AND FUEL INJECTOR - 3.0L REMOVAL / INSTALLATION or FUEL INJECTION SUPPLY MANIFOLD AND FUEL INJECTOR - 4.0L REMOVAL / INSTALLATION . Go to step 14.
13		No	Go to next step.
14	DRIVE CYCLE Connect all disconnected connectors. Clear DTCs from PCM memory using a WDS or equivalent tester. Perform fuel monitor or HO2S monitor drive cycle. See DRIVE CYCLES . Retrieve pending code. Is same DTC present?	Yes	Replace PCM. See POWERTRAIN CONTROL MODULE (PCM) REMOVAL / INSTALLATION . Go to next step.
14		No	Go to next step.
15	VERIFY TROUBLESHOOTING OF DTCs COMPLETED Perform PCM quick test. Is any DTC present?	Yes	Go to applicable DTC inspection.
15		No	Troubleshooting is complete.

DTC P0172, P0175 DETECTION CONDITION & POSSIBLE CAUSES

DTC P0172, P0175	ADAPTIVE FUEL CONTROL
DETECTION CONDITION	P0172 indicates the fuel/air ratio is too rich (RH). P0175 indicates the fuel/air ratio is too rich (LH).
POSSIBLE CAUSE	Fuel system: Excessive fuel pressure Vapor recovery system Induction system: Restricted air inlet Positive crankcase ventilation (PCV) system Improperly seated engine oil dipstick Exhaust gas recirculation (EGR) system: Leaking gasket Stuck EGR valve Base engine: Oil overfill Cam timing Cylinder compression Exhaust leaks before or near the heated oxygen sensors (HO2S)
HINT	Fuel System Monitor The fuel control system uses fuel trim tables stored in the powertrain control module (PCM) to compensate for variability in fuel system components due to normal wear and aging. The fuel trim strategy learns deviations during closed-loop engine operation. The fuel trim has two means of adapting; a long term fuel trim and a short term fuel trim system. Inputs from engine coolant temperature (ECT), intake air temperature (IAT) and mass air flow (MAF) sensors are required to activate the fuel trim system. The HO2S detects the presence of oxygen in the exhaust and provides the PCM with feedback indicating air/fuel ratio. A fuel trim factor is added to the fuel injector pulse width calculation according to the long and short term fuel trims. The long term trim values at their rich or lean limits indicate a fuel system malfunction.

PTC P0172, P0175 DIAGNOSTIC PROCEDURE

PTC P0172, P0175		ADAPTIVE FUEL CONTROL
STEP	INSPECTION		ACTION
1	Was the PCM quick test performed?	Yes	If a driveability concern or rough idle is present, Go to step 7. If any other DTC is present, Go to appropriate DTC troubleshooting procedure. Otherwise, Go to next step.
1	Was the PCM quick test performed?	No	Perform PCM Quick Test. See PCM QUICK TEST .
2	IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA Key ON, Engine OFF (KOEO). Is DTC P0172 or P0175 on freeze frame data?	Yes	Go to next step.
2		No	Go to troubleshooting procedure for DTCs on freeze frame data. See FREEZE FRAME CHARTS .
3	VERIFY CURRENT INPUT SIGNAL STATUS Key on, engine running (KOER). Access ECT V, MAFV, TP V and VS PIDs as well as BARO and LONGFT using WDS or equivalent tester. Is there any signal that is far out of specification during KOER?	Yes	Inspect suspected sensor and excessive resistance in related wiring harnesses. Repair or replace if necessary. Go to step 9.
3		No	Go to next step.
4	VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION Access ECT V, MAF V, TP V and VS PIDs while simulating FREEZE FRAME DATA condition. Is there any input signal which causes drastic changes?	Yes	Inspect suspected sensor and related wiring harnesses. Repair or replace if necessary. Go to step 9.
4		No	Go to next step.
5	VERIFY CURRENT INPUT SIGNAL STATUS OF FRONT HO2S (RH, LH) Access O2S11 PID for P0172 or O2S21 PID for P0175. Check PID under following accelerator pedal condition (in PARK): Sudden depress of accelerator pedal (rich condition) should read more than 0.45 V Sudden release of accelerator pedal (lean condition) should read less than 0.45 V Is PID reading correctly?	Yes	Go to next step.
5		No	Replace suspected HO2S. See HEATED OXYGEN SENSOR (HO2S) REMOVAL / INSTALLATION . Go to step 9.
6	INSPECT FUEL LINE PRESSURE Key on, engine off (KOEO). Connect fuel pressure gauge. Key on, engine running (KOER). Is fuel pressure within 207-448 kPa (30-65 psi)?	Yes	Go to next step.
6		No	Replace fuel pump. See FUEL PUMP REMOVAL / INSTALLATION . Go to step 9.
7	INSPECT EVAP CANISTER PURGE VALVE Key on, engine off (KOEO). Disconnect both hoses from EVAP. canister purge valve. Blow air through EVAP canister purge valve. Does air blow through?	Yes	Replace EVAP canister purge valve. See CANISTER PURGE VALVE REMOVAL / INSTALLATION . Go to step 9.
7		No	Go to next step.
8	INSPECT PCV VALVE OPERATION Inspect PCV valve for proper operation. Is PCV valve OK?	Yes	Go to next step.
8		No	Replace PCV valve. See PCV VALVE REMOVAL / INSTALLATION - 2.3L . Go to next step.
9	DRIVE CYCLE Connect all disconnected connectors. Clear DTCs from PCM memory using WDS or equivalent tester. Perform fuel monitor or HO2S monitor drive cycle. See DRIVE CYCLES . Retrieve pending code. Is same DTC present?	Yes	Replace PCM. See POWERTRAIN CONTROL MODULE (PCM) REMOVAL / INSTALLATION . Go to next step.
9		No	Go to next step.
10	VERIFY TROUBLESHOOTING OF DTCs COMPLETED Perform PCM quick test. Is any DTC present?	Yes	Go to applicable DTC inspection. See DIAGNOSTIC TROUBLE CODE (DTC) INDEX - POWERTRAIN CONTROL MODULE (PCM) .
10		No	Troubleshooting is complete.