Adaptive Fuel Control

DTC P0170, P0171, P0172, P0173, P0174, P0175 DETECTION CONDITION AND POSSIBLE CAUSES

DTC P0170, P0171, P0172, P0173, P0174, P0175	ADAPTIVE FUEL CONTROL
DETECTION CONDITION	P0170 indicates the adaptive fuel tables have reached calibration limit (Bank 1). P0171 indicates the fuel/air ratio is too lean (Bank 1). P0172 indicates the fuel/air ratio is too rich (Bank 1). P0173 indicates the adaptive fuel tables have reached calibration limit (Bank 2). P0174 indicates the fuel/air ratio is too lean (Bank 2). P0175 indicates the fuel/air ratio is too rich (Bank 2).
POSSIBLE CAUSE	DTC P0171 and DTC P0174 Fuel filter plugged or dirty. Fuel pump weak or leaking. Leaking fuel injector(s). Low fuel pressure or running out of fuel. EVAP vapor management valve leaking. Fuel supply line restricted. Fuel rail pressure temperature (FRPT) sensor reading incorrect. Air leaks after the MAF/IAT. Vacuum leaks (vacuum lines and gaskets). Stuck EGR valve. Leaking diaphragm or EGR Vacuum Regulator. Cam timing. Cylinder compression. Exhaust leaks before or near the HO2S(s). DTC P0172 and DTC P0174 Excessive fuel pressure. PCV system. Improperly seated engine oil dipstick. Fuel rail pressure temperature (FRPT) sensor reading incorrect. Vacuum leaks (vacuum lines and gaskets). Stuck EGR valve. Leaking diaphragm or EGR Vacuum Regulator. Oil overfill. Cam timing. Cylinder compression.
HINT	Fuel System Monitor The fuel control system uses fuel trim tables stored in the 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 ECT/CHT, IAT, MAP, and MAF/IAT 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 P0170, P0171, P0172, P0173, P0174, P0175 DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	Was PCM Quick Test performed?	Yes	If Misfire DTC (P0300-P0306) is present or drive ability concern is present, see DIAGNOSTIC TROUBLE CODE (DTC) INDEX - POWERTRAIN CONTROL MODULE (PCM) . If any other DTC is present, see DIAGNOSTIC TROUBLE CODE (DTC) INDEX - POWERTRAIN CONTROL MODULE (PCM) . Otherwise, go to next step.
1	Was PCM Quick Test performed?	No	Perform PCM Quick Test. See PCM QUICK TEST .
2	CHECK CONDITIONS RELATED TO MAF/IAT SENSOR NOTE: Most weather service reports are a local barometric pressure that has been corrected to sea level. However, the BARO PID reports the actual barometric pressure for the altitude the vehicle is being diagnosed in. Local weather conditions (high or low pressure areas) will change the local barometric pressure by several inches of mercury. Key ON, Engine Running (KOER). Access the PCM-LONGFT1, PCM-LONGFT2, PCM-MAF V, and PCM-BARO PIDs. Check that the BARO PID is approximately the same as the barometric pressure reading for the location, day, and altitude in which the vehicle is being worked on. BARO PID values in Keep Alive Memory require updating at high throttle openings. If vehicle is driven down from higher altitudes for diagnosing, complete three or four heavy accelerations at greater than half-throttle to allow BARO PID to update. BARO PID must be within +/- 6 Hz. (+/- 2 in. Hg.) of the altitude value in Barometric Pressure Reference Chart. See MASS AIR FLOW (MAF) SENSOR . Make BARO PID comparisons to Barometric Pressure Reference Chart or daily airport barometric pressure reports, if available. Check that LONGFT1 and LONGFT2 PIDs for all injector banks at idle are not more negative than -12%. Check that MAF V PID at idle and neutral is not greater than 30% of the normal MAF V listed, or 1.1 volts. Are two of the three checks OK?	Yes	Go to step 4.
2		No	Key OFF. Go to next step.
3	ISOLATE MAF/IAT SENSOR FROM LEAN DRIVEABILITY OCCURRENCE Due to increasingly stringent emission/OBD2 requirements, a fuel system DTC on some vehicles will be generated without a noticeable driveability concern with or without the MAF sensor disconnected. Under these conditions, if BARO_V, LONGFT1, LONGFT2, and MAF PIDs indicate a MAF sensor concern, install a new MAF sensor. Disconnect MAF/IAT sensor connector. Key ON, Engine Running (KOER). Is the driveability symptom gone?	Yes	Replace the MAF/IAT sensor. See MASS AIR FLOW (MAF) SENSOR - 2.3L . Go to step 7.
3		No	Go to next step.
4	PERFORM KOER SELF-TEST Connect MAF/IAT sensor. Disconnect fuel vapor hose from the intake manifold and plug the fitting at the intake manifold. Start engine and run at 2, 000 RPM for 5 minutes, then return to idle. Key ON, Engine Running (KOER). Perform KOER Self-Test. Check Self-Test DTCs. Are DTCs P0040, P1128, P0041, P1129, P1127, or P0402 present?	Yes	Key OFF. Disregard the current DTCs at this time. See DIAGNOSTIC TROUBLE CODE (DTC) INDEX - POWERTRAIN CONTROL MODULE (PCM) to diagnose other DTCs.
4		No	Key OFF. Go to next step.
5	DETERMINE DTC BEING DIAGNOSED Check Self-Test DTCs. Are DTCs P1131, P2195, P1151, or P2197 present?	Yes	GO to UPSTREAM HEATED OXYGEN SENSOR (HO2S) NOT SWITCHING .
5		No	Go to next step.
6	DETERMINE DTC BEING DIAGNOSED Check Self-Test DTCs. Are DTCs P1132, P2196, P1152, or P2198 present?	Yes	GO to UPSTREAM HEATED OXYGEN SENSOR (HO2S) NOT SWITCHING .
6		No	Reconnect fuel vapor line. Unable to identify fault at this time.
7	VERIFY TROUBLESHOOTING OF DTCs COMPLETED Perform PCM Quick Test. See PCM QUICK TEST . Is any DTC present?	Yes	See DIAGNOSTIC TROUBLE CODE (DTC) INDEX - POWERTRAIN CONTROL MODULE (PCM) .
7		No	Troubleshooting complete.