Dtc 171-Adaptive Learn Bank 1 High (Gasoline) - Kubota WG1605-E3 Diagnostic Manual

WG1605-G-E3,WG1605-L-E3,WG1605-GL-E3, DM
The purpose of the Adaptive Learn Multiplier is to adjust fuel flow due to variations in fuel composition, engine
wear, engine-to-engine build variances, and component degradation. The Adaptive Learn multiplier values are held
in a table and are remembered between key cycles. Adaptive memory tables are erased at battery disconnects and
with the DST.
An "update" (from Set Conditions above) can be thought of as a "variable timer", one that takes longer to set a
fault at low engine speeds than at higher speeds.
This fault of DTC 171 sets if the Adaptive multiplier exceeds the high limit of normal operation indicating that the
engine is operating lean (excess oxygen) and requires more fuel than allowed by corrections. Often high positive
fueling corrections are a function of one or more of the following conditions: 1) exhaust leaks upstream or near the
HEGO sensor, 2) reduced fuel supply pressure to the fuel injection system, 3) a inoperative sensor, 3) an injector that
is stuck closed or dirty, 4) weak spark or lack of spark to a cylinder and/or 5) a MAP sensor that indicates pressure
that is lower than true pressure.
This fault of DTC 172 sets if the Adaptive multiplier exceeds the low limit of normal operation indicating that the
engine is operating rich (low oxygen content) and requires less fuel than allowed by corrections. Often high negative
fueling corrections are a function of one or more of the following conditions: 1) an inoperative O
supply pressure or temperature, 3) internal mechanical engine damage, 3) an injector that is stuck open or leaking,
and/or 4) improper airflow through the engine due to things such as valve timing problems, collapsed lifters/followers,
worn cam lobes or bent pushrods.
To test the O sensor run the CL test. This test tests both pre-cat and post-cat O
2

DTC 171-Adaptive Learn Bank 1 High (Gasoline)

Diagnostic Aids
NOTE
• If any other DTCs are present, diagnose those first.
• Oxygen Sensor Wire-Sensor may be mispositioned contacting the exhaust. Check for short to ground between
harness and sensor and on sensor harness
• Inoperative Oxygen Sensor-sensor may be damaged internally and unable to switch resulting in a system that
over fuels or under fuels the engine.
• Weak Spark or Lack of Spark to a Cylinder-improper burning of the fuel/air mixture in a cylinder results in excess
unburned oxygen exiting the cylinder causing the pre-cat O
• Vacuum Leaks-Large vacuum leaks and crankcase leaks can cause a lean exhaust condition at light load.
• Injectors-System will be lean if an injector driver or driver circuit fails. The system will also be lean if an injector
fails in a closed manner or is dirty.
• Fuel Pressure-System will be lean if fuel pressure is too low. Check fuel pressure in the fuel rail during key-on,
engine off and during normal operating conditions.
• Air in Fuel - If the fuel return hose/line is too close to the fuel supply pickup in the fuel tank, air may become
entrapped in the pump or supply line causing a lean condition and driveability problems.
• Exhaust Leaks - If there is an exhaust leak, outside air can be pulled into the exhaust and past the O
causing a false lean condition.
• Fuel Quality - A drastic variation in fuel quality may cause the system to be lean including oxygenated fuels.
• System Grounding - ECM and engine must be grounded to the battery with very little resistance allowing for
proper current flow. Faulty grounds can cause current supply issues resulting in many undesired problems.
• If all tests are OK, replace the HO
2
S sensor with a known good part and retest.
2
1-165
sensor functionality.
2
sensor to see a lean condition
ECM SYSTEM
sensor, 2) high fuel
2
sensor
2
KiSC issued 12, 2016 A